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stevenmarston

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Sealed or Vented? We want to hire a plumber to install a new heating and plumbing in our home. It seems that before we can get proper quotes or make progress, we have to make a fundamental choice between using a sealed or a vented system. It’s a large house (six bedroom), and we’re a large family of two adults and four teenage children, and our highest priority of all relates to water pressure. It’s vital that we can at least have a system which allows us to be running three or four power showers, at the same time, and not have the water temperature or pressure affected if someone then turns on a tap or the dishwasher starts up etc. Right now, this doesn’t work at all with our current system, even with one shower on, if a tap goes on too then we’re either scalded or frozen, or both alternatively.

I know little of the two system choices, other than the snippets I’ve picked up from plumbers so far. I’m told the advantage of a sealed system is no water tanks or pipework in the attic (so nothing to freeze), less risks of leaks going un-noticed and less risk of air locks (especially in an old house like hours where pipes do tend to go up and down a lot to get around the layout of the house), but with the disadvantage that cold water is based on mains pressure and the hot water only works on pressure, no pump like a vented system would have, so the more taps/showers that are on, the lower the pressure and the more likelihood of temperature changes when taps are turned etc. I’m told the advantage of a vented system is that the water supply to the showers will be from stored water (hot and cold) in the tanks, so constant pressure to all showers until the tanks run dry and much less impact of taps being turned on etc, but the disadvantages are tanks and pipes in the attic that can freeze, leaks can go un-noticed as no drop in pressure and higher risk of air locks…

How on earth am I supposed to make this decision which way to go? I only know I want us all to be able to have a shower without being scaled or froze when the dishwasher starts or one of us stops our shower (and of course I’d prefer not to have frozen pipes, leaks and airlocks). Can anybody help me shine some light on this, how to make the decision, are there other things to be considered, are there ways around the disadvantages of either solution? We really need help here…

Addition: Some replies I got asked about our current cold water pressure. I did a test, using the kitchen tap which is about as close to the mains as possible, I'm getting 10 litres per minute, though it's much slower if I go to the upstairs bathroom taps, less than half that.
 
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I have sent a private message to one of our members, CHRISM, who seems very knowledgeable about plumbing practices in your area. He should be able to provide a much better answer than I am able to.
 
What you need are pressure balanced shower valves. This evens the pressure of the two sides (hot and cold) when one loses pressure ( Toilet flushing or DW running)

To increase volume the best way would be to increase the size of your main and runs to each fixture. The storage tank idea is just problems waiting to happen! IMO
 
StevenMarston - `Sealed or Vented`??

"Hello Steven" - I was alerted to your enquiry by a `Private Message` from Phishfood a Senior Member [USA]
I am a Building Services Engineer from London [UK] - I started off as a Plumbing Apprentice - Qualified - went on
to obtain a HNC in Building Services Engineering - Studied and Qualified in all [possible] aspects of Domestic and
`Light Commercial`Heating - I have `Run` my own Plumbing, Heating and Gas Installation Company for over
30 Years - I also Studied and `Earned` my `Msc. Degree in Building Services Engineering.

I have listed all of the above to `exhibit` my `Qualifications` in commenting / answering your Questions about
installing Plumbing/ Heating into Your property, - NOT to try to obtain Work from You [ I am based in London ].

UNFORTUNATELY - I have JUST seen the `Private Message`& Link to Your Post - and I am not able to answer
any of your points NOW [ 2200HRS].
I am away from Home for 2 Days - but I may be able to Post some suggestions on Sunday [?].

Your property size and occupancy / demand for Power Showers etc. DOES `complicate`matters with regard to
Water Volume - Pressure - Pipe Sizing - Hot Water Volume - Temperature etc.

Almost certainly You WILL need to have the Incoming Water Main Pipework increased in size - Diameter - to provide MUCH MORE than 10 Litres per Minute - whether STORAGE of Water - OR - MAINS SUPPLIED Plumbing is
decided upon.

That `First Comment` will be the `Start` of some Detailed Suggestions - although when I design Plumbing & Heating Systems - I ALWAYS start with a `Site Survey`- otherwise what seems perfectly `feasible` - is often
negated by something at the Property - not on the Drawings !!

I will TRY to explain the `Benefits` & `Drawbacks` of Systems and the `Requirements`- BUT - For example
`Accommodating` LARGE Hot Water Storage Vessals whether `Tank Fed` or `Mains Fed` can be EXTREMELY
Difficult in relation to their SIZE and running LARGE ENOUGH Flow & Return Pipework to Heat the Water contained
within them. [ From the Boiler]

Also - Hot & Cold Water `Distribution Pipework` can be Difficult to `Run`- LARGE sizes cannot usually be
`Accommodated` by notching into `Normal Size` Joists - Joists can only be `Notched` to a MAXIMUM of an
EIGHTH of their Depth - This can be a Problem running Pipework throughout a Large Property.

I don`t want to IMMEDIATELY seem `Negative` about this - BUT to get the recommendations CORRECT - I may
well want to ask a LOT of Questions - even then there is NO Substitute for `On Site` Viewing - WE could correspond and I could offer You my BEST `Technical Suggestions`- only to find that a Plumber / Heating Engineer goes on Site and finds Fault with some of those `Technical Suggestions` !! - Because of something
within the Building Construction / Layout that I was not aware of.

Steven - I hope to have time to Post some further comments on Sunday [21st] - Although I will be travelling back Home on that day - and may be `too tired` to `Post` coherently after that [?].
If I do not respond on Sunday [PM] - I will do so on MONDAY 22nd.

"Sorry" that I could not reply with more detail tonight - I am actually `away` to have a `Break` from
`Work`.



"Regards", CHRISM.


P.S. "Thank You Phishfood" for `recommending` me - although this `System Recommendation` WILL NOT be
in any way `Straight Forward`!
 
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Hi Chris - Finally, it's fantastic to hear from someone so qualified in this topic, as I'm just going round in circles with the advice I'm receiving and I have no idea which way to turn anymore. I am absolutely happy to provide any information you need, I can provide floor plans of the house if that will help, and any other information you need to be able to assist. As this project is going to cost many thousands of pounds, no matter which solution I go down, I really want to make the right fundamental choices and not be regretting later that I spent all that money and still only one or two people at a time can take a shower in the house - With four teenage children, that is the over-riding requirement, that at 8am every day, we can all take a shower without cursing each other...

Upgrading the mains, seems a good idea anyway, whichever way we go, so that's something I can already start to initiate with the water board... Though of course if the pipework internally in the house isn't up to the job, it will make little difference until that is resolved as well.

So far, in answers I've got from various plumbers and posts, the answers seem to almost be 50/50 split between sealed and vented, which is scary, I guess there really is no right or wrong here, just options. Many seem to think that with an improved mains and decent pipework, four simultaneous showers with thermostatic valves could do the job using a sealed system, but others are far less confident and recommend using pumps for the showers which means a vented system I assume, to get the constant pressure...

Any help you can give, would be truly appreciated... Any questions you have, just let me know
 
"Hello Steve", I will try to explain about the Systems that You are asking about - in part
to give information to our colleagues here in the Forum, So THIS may not `inform` You any
further than the knowledge that You already have - BUT - initially I should `Post` some info.
so that our U.S. Colleagues know what we are writing about.


YOUR particular requirements of being able to use 4 Power Showers at the same time - in your
Home - without these Showers negating the Water Pressure in a `noticable`way - and that the
use of other Water Outlets should not lower the Water Pressures either - is quite a Design Challenge.

Every type of Pipework System has Pressure Loses - relating to the amount of Water being transported
and the amount of Pipework & Fittings - Every Metre of Pipe and Every Fitting & Valve has a Negative
Effect on the Flow of Water through those Pipes - And Every Outlet - Tap, Shower, Washing Machine,
Dishwasher etc. that is being used WILL lower the Pressure and Flow Rate [Volume] throughout the
Pipework System - whatever System is Installed.

There is not a Design in a `Domestic situation` where NO Pressure loss is achievable - The Best that
can be done is to achieve Sysyems where even with the Pressure Loss - the Showers etc. - in Your case
are still `Satisfactory`.

The reason that this will be `Difficult` to achieve - whichever type of System is decided upon - is that
in a `Commercial` situation - E.G. a Hotel - the Plumbing Pipework is VERY Large in comparison to the
sizes that can usually be installed in a House.
In a Hotel there will be Ducts adjacent to the Bathrooms in which the Hot & Cold Pipework is `Run`-
these are Very Large Pipes - More than capable of supplying all of the requirements of the Bathrooms
that they supply - Powerful Showers etc.

Also - the Hot Water Storage Cylinders [Calorifiers]and Cold Water Tanks are `Massive` in comparison
to all but the `Biggest` Houses.

Regarding `Sealed or Vented`:

`Sealed Hot Water system`:

In the U.K. a `Sealed` Hot Water System is classified as an `Unvented Hot Water System` - The Hot
Water Cylinder [Tank - U.S.] is a Pressurised Storage Vessal which is supplied by the Water Main - to
provide Hot Water at similar pressures to the `Average Mains Pressure`- USUALLY not much more than
30 PSI - but that depends on IF that pressure is available at the location of the `Cylinder`.
SOME Mains Pressures are so High that they have to be Restricted prior to the connection to the Cylinder
for correct operation / not to cause damage to the Cylinder or Control Valves etc. - BUT - even then the
Hot Water Pressure - leaving the Cylinder is not more than approx. 35 PSI. The VOLUME of Hot Water provided depends upon the Inlet Size to the Cylinder and the Volume that the Mains Water Supplys
at that Inlet point to the Cylinder.
THEN there will be some `loss` of pressure because of `moving` the Stored Hot Water out of the
Cylinder - and also the `Frictional Loss` of Pressure through the Pipework.

These `Unvented Cylinders` are usually Heated by `Flow` & `Return` Pipework from the Domestic Heating Boiler
although they can be Electrically Heated - the LARGE Sizes use more than one Immersion Heater.
Some Installations require a Boiler `Dedicated` to Heat the Cylinder ONLY - whether because of NOT
`Upsizing` the Domestic Central Heating Boiler `too much` [re Energy Efficiency] - OR because of the
`Flow` & `Return` Pipework `Runs` being shorter from a `Dedicated` Boiler than from the `Main` Heating
Boiler.
THAT of course requires a LOT of `investigation` and `calculation` - and when pondering this option one
MUST take into consideration the GAS SUPPLY to your Home - Gas pipework again has `Restrictions` in the
`Flow /`Volume` of Gas carried - Every Metre of Pipe and Every Fitting restricts the Flow/Volume carried by
the Gas Pipe - and EVERY Gas Appliance that is used WILL negate the Flow / Volume carried by the Gas Pipe.

This is another `Design Factor` that You will have to take into consideration when designing your Homes
Heating and Plumbing Sysyems - deciding on HOW you intend to HEAT the Hot Water is part of deciding
which type of System you install on the `Plumbing Design`.
KNOWING that you CAN Heat the Cylinder in such a way determines WHETHER you choose a particular
type of Sysyem.

PART of the Selection Process would be:

Can I Construct a `Cylinder Cupboard` [Fairly Big] to House whichever [Big] Cylinder that is selected -
can this be `Adjacent` to the [New ?] Bathrooms / Shower Rooms - regarding the installation of Large
Pipework in and around the Cylinder Cupboard / From Tank in Roof Space - BUT - NOT all around the House ??

Can I Construct a Tank Base [very strong/well built] in the Roof Space - NEAR to the Cylinder Cupboard
to support a Large Cold Water Storage Tank - installing the Pipework from the Tank down into the Cylinder
Cupboard - so as to NOT have `Long Runs` of Large Pipework ??

Would it be possible to Install a `Dedicated` Boiler [Heat Only] to Heat the New Large Cylinder - in a
`Suitable Location` for the FLUE and Condensate Drain Pipe [To Outside] - AND will I be able to `Upgrade`
the Gas Supply to Supply that Boiler AND the Central Heating Boiler - plus Cooker and any Gas Fires etc. ??
Or would it be `better` to Heat the Cylinder from ONE Boiler - Taking into consideration that this would
be a Bolier which would be classified as `Commercial` - not `Domestic`and would require a Gas Engineer /
Gas Installer with `Non - Domestic` Qualifications / Registration - with `GasSafe` [U.K. Gas Registration ]

What size are the JOISTS in your House ? - have You got anywhere that you can lift a Floorboard on the First
Floor - although they are unlikely to be much different to the `Norm` - it is possible that You have `BIG`
Joists - which would enable Larger Pipework to be Installed than in the `Average` House.

Unvented Hot Water Storage Vessals are manufactured in various sizes - BUT - even if a suitable
size can be determined regarding the Hot Water Requirements of the House - there is usually a
`Problem` installing BIG ENOUGH Pipework to transport the Hot Water around the House to the various Bathrooms/Showers etc. - without the loss of Pressure/Volume that would `negate` the `Satisfactory Use`
of the 4 Power Showers and allow usage of `other` Water throughout the House.

This Pipework Size `Problem` will apply to whichever System Type - `Sealed` or `Vented` is chosen.

`Vented Hot Water System`:

In the U.K. this type of Hot Water System has been the `Most Popular` for many Years in Homes - it
consists of a Hot Water Cylinder - supplied from a Cold Water Storage Tank [Usually in the Roof Space]
These are usually heated by `Flow` & `Return` Pipework from the Domestic Central Heating Boiler,
although in smaller properties `Direct Heating` from an Immersion Heater [Electric] is sometimes used.
There are Large Size Directly Heated Unvented Cylinders - they have more than one Immersion Heater.
The installation of a `Dedicated` Boiler to Heat this type of Cylinder is also a consideration.
The `Vented` classification relates to the `Open Vent` Pipe that rises from the Cylinder Top to then
penetrate through the Lid of the Cold Water Storage Tank that supplys the Cylinder - THAT Vent Pipe
is a Safety Discharge Pipe - in the event of an Expansion of Water - because of an `OverHeat` situation
primarily - or because of a situation leading to an `Over Pressurisation` of the Hot Water System -
although the Vent Pipe being `Blocked` may NOT provide that `protection.

Immersion Heaters should always be installed as a `Back Up` - in case of Boiler Failure - where
the Heaters are within the range that can be supplied from the Consumer Unit. [Electrical Fuse Board]

The question as to WHICH type of System would be more suitable for Your Property has NO Immediate
Answer - IF one of these TWO Types of System has to be selected - one of the MAIN Problems will be
the LARGE SIZES of the Hot and Cold Water Services - and Installing those LARGE Pipes around the House.

IF VERY Large Hot Water Storage is to be Installed - a purpose provided area must be constructed -
taking into consideration the Weight of the Cylinder [either type] - AND the Distribution Pipework FROM
there throughout the House.
ALSO - If a Cold Water Storage Tank is to be installed - it will be a VERY HEAVY item - it would NOT be
suitable to install a 50 / 70 Gallon Storage Tank in Your Property - it would be MUCH LARGER - with the
necessity of Constructing a STRONG TANK BASE - to Water Regulation Specifications - with an `Access
Route` for `Maintenance`.

Installation of Boilers has to be `surveyed` in relation to Where they can be CORRECTLY Installed - AND
the GAS REQUIREMENTS - regarding the Pipework / Pipework Restrictions [ Supply of Volume]

Steve - this MAY have supplied more Questions than answers - BUT - I wanted to just show You SOME
of the MANY `Considerations that WILL BE required to decide on which type of System that You Install !!

EVERY Property is Different in the Requirements relating to Hot Water Usage / Hot Water Storage / Cold
Water Storage / Mains Supply - How to Heat the Hot Water - the Distribution of the Hot and Cold Water
throughout the House - Amount of Bathrooms / Shower Rooms / Other Water Outllets - What Specification
of Taps [Faucets] Showers etc.

Because the `Norm.` is NOT a Home such as Yours - with the requirement to be able to use 4 Power Showers
at the same time - whilst water is still being used in other parts of the House - Designing the appropriate
system without Constructing the Bathrooms / Shower Rooms around / adjacent to a Purpose Built Cylinder
Room - with either a Large Tank above - WILL BE Difficult regarding the loss of Pressure / Volume of Water
that You quite rightly do NOT want to have.

I feel that I should mention - although I know that You are aware that the new Plumbing & Heating Works
will be `Costly` - A friend of mine had similar requirements to You regarding he wanted to be able to use
3 Showers and water in the Kitchen each Morning - When the `Major Works` were calculated & costed he was
`Horrified` at not only the Costs but also the `Disruption`to his Home that the Works necessitated.

An option that I gave to Him - to achieve the Showering requirements was to have his `Incoming Water Main`
size increased - Run a new `Rising Main` throughout the House [Larger] - Install 3 `Mains Fed` Electric Showers
- I believe that He had to get the Incoming Electrical Supply Fuse increased in Size to accommodate this also -
by His Electricity Supplier.
IF You wanted to explore that option - You should in the First instance ask your Electricity Supplier about the
possibility of doing that - I believe that in certain parts of the Country it is not possible to `Upgrade` the
Incoming Supply Fuse ?? - regarding the fact that the extra power is `not available` - although your Home
MAY have a `Larger` Incoming Fuse than smaller properties and You might have the available power to supply
SOME Electrically Powered Showers ??

Because of the vast increase in VOLUME of Water available - which obviously would have to be checked with YOUR Water Supplier - He was able to use all 3 Showers to His Satisfaction - I cannot remember WHICH
Manufacturer / Model of those Showers - BUT - I would have Specified the `Best Quality Manufacturers`.

I have mentioned THIS - ONLY as an Alternative - BUT - If You are going to `Replumb` the entire House you
might have Bathrooms / Showers where an Electrically Powered Shower would be `O.K.` - in relation to what
could be `extreme costs / works` to have a `Power Shower` Installed ??

Because I have NOT been able to preview this - prior to `Posting` - I hope that it does not seem to be
`rambling` - I started off as I mentioned to give some descriptions regarding the `Sealed` & `Vented`
Systems - BUT - while I was writing I thought of `other` points to `mention` - in passing.
Scrolling back - I am sure that THIS will look a bit strange when viewed as a Page of Text - if so - "Sorry"
I have had a VERY busy Day - on returning after my Weeks `Break`.

As I know THIS will probably have `confused` you more than You were before - BUT - perhaps it will
enable You to formulate some specific questions that I will then answer - I wanted to `SHOW` that
`Sealed` or `Vented` is NOT a Simple / Answerable Question - without `LOADS` of Calculations and
probably Construction / Alterations to the Building Layout [?].

THAT is WHY You have not been able to get a `Definitive Answer` from Plumbers - they cannot answer
without knowing `masses` of Information about everything that I have `mentioned` in this Post - AND More !

I look forward to Your response - "Sorry" that I cannot sound more `Positive` !!


"Regards" CHRISM.
 
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"Hello Steve", Some of the above details are NOT applicable to Your House - as I have SINCE POSTING found out that you have OIL Heating - NOT GAS - so unless You plan to change that - what I stated about the Gas Supply being adequate to supply ALL the demands of the House Heating etc. - would now transfer to the
OIL Supply being adequate for any Boiler Upgrade that might be required when the Heating of the Hot Water Cylinders is calculated.

I have noticed that this Text is being `disrupted`- I don`t know why this [often] happens - I try not to type too many words on each line - but still it
happens - please excuse me for NOT wanting to `Edit` out these disruptions
at 22.25HRS this evening.

I look forward to your reply and further questions - although I may NOT be able to respond IMMEDIATELY [?].


"Regards", CHRISM.
 
Hi Chris,

Thanks so much for all your information, as you say, it is a lot to take in, and also quite some questions where I think if I can provide you with more information, you can then help me further. I will give it all some thought, and come back to you when I have the information you need. Thanks.

Steve
 
"Hello Steve" Thanks for your reply - by all means take as long as you like to formulate
some questions - So that I don`t have to keep coming to the Forum to see if You have
`Posted` anything - could you send me a message when You are ready to ask the questions.

Although I do come to the Forum `regularly` sometimes - because I am very busy at Work
at present - I will not be `visiting` as frequently for a while.


"Regards" CHRISM
 
Hi Chris,

Thank you so much for your ongoing help and time, it's very much appreciated....

Some possible answers

In terms of the boiler – As you rightly said, we are oil based here. I think for the purposes of giving help to me, you can assume that we will install a single boiler that is sized sufficiently to be able to heat all the water we will need for heating and hot water tanks, it will be a commercial boiler as domestic boilers are not big enough, and it will be sited on our ground floor in a purpose boiler room. I do not think we would have a dedicated boiler just to heat the hot water in the cylinders, though I cannot discount it entirely as an option if it’s advisable, but preferably we’d like to do it all from one large boiler. I think getting an oil supply to such a boiler would be challenging.

I would expect we would have a back up immersion heater in each hot water tank, just in case of boiler problems. I do not think this will be an issue in terms of electricity supply as our current hot water tanks (of which there are two) also have immersion heaters.

Our electricity supply is relatively flexible, this used to be a farm with three phase electricity which is now downgraded to one, but I think that due to it’s history, it has quite a large supply if needed for immersion heaters and electric showers etc. if they form part of the solution.

You can assume, again for the purposes of giving advice, that if it’s needed, we do have sufficient room, close to the bathrooms, to build cupboards for hot water tanks, albeit that to save lot’s of pipework, it might be easier to have two tanks, spaced out evenly in the top floor, which would also give us a higher volume of water storage.

You can assume that we have plenty of loft space, so if needed, there is scope to put large header tanks into the lofts above the hot water cylinders if needed for a vented system.

I have lifted our floorboards in the first floor, and can confirm that I think our joists are pretty average, they are about 8 inches deep which I think is fairly normal. Also, I should say that we don’t have floorboards in much of the first and second floors, the floors are about 50% floorboards and 50% solid (lime ash), so we will have to be running a lot of pipework either along the bottom of walls in boxed in sections, or taking it up into the loft spaces, then back down into the rooms again.

Some questions

You mention that with a sealed system, the highest pressure of water leaving the cylinder is going to be around 30 psi as the systems can’t cope with more than that… So does that mean the pressure of water, heading toward the showers, is about 30psi? Does it also mean that if four showers are running in parallel and nothing else, then they share that 30psi equally (minus some loss for friction), so each gets around 7psi? How does that compare with a vented system, incorporating a pump per shower, what pressure would the pump be able to deliver water from a vented hot water tank combined with a mains cold supply at 30psi (assuming the size of the pipework is the same for both systems)?

You mention that a friend of yours was horrified by the costs involved in installing a ‘super’system – How horrible were those costs, can you give me some idea?

You mention your friend in the end went with electric showers – Have you any idea what kind of water volume or pressure he was able to get out of each of the three showers when they were all running?

Given all the above information, so to summarize, we could build hot water tank cupboards, we do have plenty of loft space for large header tanks, we do have decent electricity and oil supply and almost certainly could manage with one commercial boiler, we don’t have large joists and not all upper floors are wood, but we could live with pipework going up into the loft and down again, or running in boxed in sections along walls and we are currently renovating the house, so disruption is expected… What solutions are most likely to give us the best chance of meeting the main requirement, four power showers running in parallel, and still able to switch on dishwasher or washing machine without anyone noticing? And what are the comparable costs of the possible solutions (i.e. is one three times more expensive than another, or are they similar etc)… What would the impact of the solutions be on things like frozen pipes, airlocks, leak risks etc..

Any help you can give, would be much appreciated.

Best regards,

Steve Marston
 
CHRIS RESPONDED TO ME AS BELOW BUT HAS NOT HAD TIME TO POST IT YET TO THE FORUM SO I AM DOING IT ON HIS BEHALF:

SOME ANSWERS TO YOUR QUESTIONS ABOUT PLUMBING SYSTEMS

Regarding the Pressure of approximately 30 psi of Hot Water at the point
of `Leaving` an Unvented Cylinder - You asked if the 4 Showers would then
`Share` equally this Pressure at approx. 7 psi [minus Friction Loss].

Calculating Pressure Distribution & Loss to exact parameters is `Impossible`
without knowing the Size of Pipe - Route of Pipe work - Amount of Fittings &
Valves - Flow Rate of the Shower `Roses`- plus Flow Rates of other Taps and
`Outlets`.
However - the Pressure would NOT be shared as you described - depending on
where / which Shower was in use - differing Pressure Loss would occur.

The most important factor regarding Hot Water Usage on `Multiple Showers`
is that there is sufficient VOLUME of Water available - WITH enough Pressure
to `Push` the Water to all Showers.
This can be achieved by ENSURING that enough Water VOLUME is contained
within the System - Tank - Cylinders and Supply Pipe work - and ALSO
ENSURING that the Incoming Water Main can supply enough Water to the
System & TANK so that the Tanks cannot `Run Dry` during `High Usage`
of the Hot Water and Cold [Stored] Water Down Services.

This is where the `Large Pipe work` that I previously mentioned comes into
the design of the Systems - Pipe work must be Large enough to Supply ALL
of the `Outlets` - Showers and all other points, with Pumps on the Supply's
to Showers & Bathrooms - if they are to be installed.
The Pipe work sizes depend upon the VOLUME of the `Draw Offs`.

When I wrote about the Hot Water Cylinders being `Sited` close to the
Shower Rooms / Bathrooms the idea of that was to perhaps install LARGE
Pipes from the Hot Water Outlet of the Cylinder within the Cylinder Cupboard
and to `Tee Off` the Hot Water Supply's to the Showers / Bathrooms from
those large Pipes - creating `Manifolds` within the Cupboards - so NOT needing
to `Run` Large Pipe work under Floors or around the walls [low level].

Something that affects WHICH TYPE of Hot Water Cylinder is Installed is that
Domestic Unvented Hot Water Cylinders do NOT have LARGE Outlets for using
Large Pipe work - `away` from the Cylinder, generally the outlet sizes are not
larger than 22mm - which would be Totally Inadequate.
It MAY be possible to obtain `Commercial Sized` Unvented Cylinders - with
LARGE Hot Water Outlets - although these would probably be prohibitively
expensive - AND possibly Too Large in Dimensions to use in Your Home - ??
Unfortunately - I have not had the need to Install anything of a Commercial
Size recently - so I do not have any Details / Sizes / Costs to hand.

Large Capacity Copper Hot Water `Indirect` - `Vented` Cylinders - E.G. 450 Litre - CAN
be Ordered with LARGE size Outlets - and must be `Pre-Insulated` with
Spray on Foam Insulation.
These `Vented` Cylinders are Supplied from Cold Water Storage Tanks - which in your
System would be Large Capacity - hence Large in Size and Very Heavy.
If these Tanks are installed - the Bases MUST be constructed to minimum specifications
to `Spread the Weight' and `Fully Support` the Tank and associated pipe work.
I would also recommend - if it is possible - that You have a `Housing` constructed for
the Tank which would be Insulated well [except UNDER the Tank] - to `Protect` it
from `Freezing Temperatures`- the Tank also having a `Good Quality` Tank Jacket - and
ALL Pipe work being Insulated - in a `Professional `manner - to Water Regulation Specifications.,
this involves Pipe Insulation of MUCH LARGER `Wall Thickness` than You might imagine -
there are MINIMUM size specifications to adhere to the Water Regulations.

If `Vented` Cylinders are installed - supplied from LARGE Cold Water Storage Tanks -
the Cold Water Supply to the Cylinders should be at least the same size as the Hot Water
Outlet - Depending upon further System Details - we could be talking about 42mm or 54mm Copper Pipe
for the Hot Water and Cold Water Services - WITHIN the Cylinder Cupboard - THAT will
also depend upon calculating the DEMAND for `Water Draw Off`.

When calculating the amount of Hot and Cold Water Draw Off - You would need to have
an approximate `Maximum Expected Time` allowed for each Shower - MULTIPLIED by
the amount of Litres per Minute that the Showers AND other Draw Offs - used at the same
time would `normally` use.

I would be fairly sure that You would be better installing 2 Cylinders - as a VERY Large `Draw Off`
from ONE Outlet is NOT Ideal - IF this could be `Split` between 2 Cylinders - ALSO - That
would make the Pipe work `Manifolds` easier to install - Less Pipe work in each Cupboard,
More room for Pumps in each Cupboard - Less Pipe work to be `Run` to each Shower / Bathroom
etc. - BUT - of course You may have to install 2 LARGE Cold Water Storage Tanks.

The Cold Water Services should also be of the Same Size as the Hot Water Supplies -
Again perhaps LARGE Pipe work within the Cylinder Cupboards with the Supply's to
the Showers and Bathrooms `Teed Off` within the Cupboard.

Although You want to be able to have `Power Showers` - for the purpose of ensuring
that the Showers do NOT require too much Volume of Hot Water [and Cold] - You should
definitely consider Shower Valves that have 15mm Connections - it may also be necessary
to install `Flow Limiters' to the Inlets to the Shower Valves - which would ensure that the
`Nearest` Shower / Other outlet to the Cylinder / Pumps did NOT diminish the Flows to
the other Showers / Outlets - This sounds like it would `Negate` the idea of Power Showers
but it is still perfectly feasible to have GOOD Showers with the Flows `Regulated`.

I should mention to You that to expect REALLY High Volume & Pressure Showers would be
`unrealistic` from a Design point of view - You would be `Going Beyond` what is possible
to achieve in a `Domestic` situation - BUT - You will be able to achieve `Good Showers`.

With regard to running Pipe work up a floor and then back down again - that is NOT to be
recommended - apart from any [?] Air Lock considerations - the effect upon Pressure would
be detrimental.
This can be done with `Pressurised` Pipe work - BUT I cannot recommend this for Your
Systems - especially not being able to `Survey` the House to view / decide on Pipe work
`Routes`.

When I mentioned about `Upgrading` your Incoming Water Main and possibly Installing
Electrically Heated Showers - this would TOTALLY depend upon the available VOLUME
and PRESSURE that could be obtained - THROUGHOUT the House - sometimes the Pressure
can be `So Good` that Pressure Limiting Valves have to be installed on the supply's to
the Electric Showers to prevent them being `Over Pressurised`.
The VOLUME must be enough to `Satisfy` ALL of the Demands of the Showers AND all
other Mains Water Draw Offs - without any Draw Off `negating` the Showers etc.

When I mentioned my Friend who installed 3 Showers on an Upgraded Water Main -
He was happy with the `Results` - Unfortunately we did not carry out the Installation
- as his Brother is a Plumber - when my Friend originally wanted to `Find Out` about
Upgrading his Plumbing - basically `Re-Plumbing` his Home - I did some `Rough`
Calculations for Him - and described to Him the `Disruption` of His Home that would
be involved in a `Total Re-Plumb` - His Brother was not experienced in `Pricing or Design`.
I have no memory of the Water Volume and Pressure that was achieved - He `Upgraded`
the Water Main after enquiring from the Water Supplier what Volume / Pressure would
be `Supplied` - which was more than adequate to `Support ` 3 Electrically Heated Showers
and his other Mains Water Outlets.

My comment about Him being `Horrified` about the Costs & Disruption was probably
the `Wrong Thing` to write when corresponding with You - He had NO idea of Costs
and somehow did not `realise` the amount of Disruption that the `Proposed Works`
would cause, So He was shocked when He found out these things.
I do not have any of the `Costs` documented still - it was quite some time ago - as
We did not do the Works that were decided upon - We did not keep the `Records`.

Regarding Your question about the `Relative Costs` of an `Unvented` or `Vented`
Hot Water System - As there are `reasons` why Unvented will probably NOT be
suitable for Your Home - Hot Water Outlet Size NOT being Large enough for example
- and the Fact that `Pricing` Your Systems would be a `Massive Task` - as a `Favour`- and
without being able to `Survey` the House and even then a Complete Design would
be required to be able to do the `Costs` - I cannot give You even a `Guide` to the
prospective `Costs` - Sorry if that is `Disappointing`- but I hope that You will
understand.

I HOPE that this does not read as `Confusing` - and I imagine that it will prompt
more questions than perhaps it has answered - Trying to give advice on Your Home
Systems - without ever being able to do `proper` Surveys is very `Demanding` and
it is possible that pertinent items would be missed.
This is `quite a task` when we do it as a Commercial Project - and we then can Visit
Site as often as is `Necessary` - even then it is very `Time Consuming`.

I hope that this is helpful - even if it gives You more `Options` to consider - I have tried
to comment on all of Your questions in your Email / Post on the Forum [?].
 
"Thank You very much Steven" - for `Posting` the Information when I was not able to do so.

By all means take Your time to go through the Details and then perhaps You will have some more questions.

I should mention for `Others` on the Forum that I am NOT able to be exact on anything because I would need MUCH more
Detail - Exact Drawings/ Proposals - Site Surveys etc. - Details of ALL of the Shower Valves and Taps [Faucets] Flow Rates or Flow Limiters - AND have to be able to work out exact Pipe Routes / Numbers of Fittings & Valves/Pumps etc. - To give `Calculated` Information.

THAT IS Possible in a `Commercial Situation` - where I would be providing the `Detailed Information`and Design for `Contracted Works` - BUT - Unfortunately the `Work` involved in doing that is far too much for `Advice`
on this Forum.

I have mentioned this here to explain WHY my Information to Steven is `General` - not `Specific`.

I hope that my Information will still be of some help Steven.


"Regards", CHRISM.
 

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