Home Run System with Manifolds

Maybe I missed something but YOU SAID:
" Since 3/8" pex tubing doesn't exist in this part of the country I had to settle for the next best thing which is polyethylene tubing with an inside diameter of 0.375". 3/8" pex has an ID of 0.360" and a cross sectional area that is 92% as large as this polyethylene tubing. Even though the PE tubing is not really pex, from now on I'm going to refer to it as 3/8" tubing."

Does that mean you are going to use that in your new home as well?
Or was that just for testing purposes?


Not sure why you are so bent on using 3/8 tubing. Easier to install?
I doubt it. seems like more trouble to adapt and reduce.
Look to the future as well. need to repair or modify. Parts are going to be more difficult to find.

I am impressed by your diligence to set-up and test your theories.
You asked for suggestion on making connection and got more than you expected.
Like Frodo Said do what you want, just remember the old saying.

Thanks for pointing that out... I absolutely do not intend on using the polyethylene tubing in the new house, it's just the closest thing to 3/8" pex that I could find at the local hardware store.

It's not that I'm bent on using the 3/8" pex per se it's just that I see a potential for it's use and what I'm bent on is finding out for myself if that's really true. I'm not the type to do something just because everyone else does and I see a worthwhile reduction in water and energy usage by reducing the size of the supply lines from the standard 1/2".

I'm building a superinsulated passive solar house, which in and of itself is totally unheard of and met with sharp criticism around these parts. A passive solar house would be considered "too high tech" by most people despite its use 1000's of years ago. Ironically, their computer controlled "smart" thermostats, furnaces and gizmos are just fine.

My calculated heat load is ridiculously low... to the point where water heating is my principal energy usage. If I can cut down the amount of hot water wasted and get near instantaneous delivery to my fixtures just by choosing the right pipe size then that represents huge savings in my case.

The parts aren't necessarily hard to get and choosing the right ones won't require adaptation to other sizes. It's just that I have to order them in at the local plumbing supply store since they don't stock them.

As for remodelling, that would normally require a tearout to the point where it would be easy to run a larger plumbing line from the utility room anyways. All of my water use areas share a common wall with my utility room so it's all accessible and ready for a relatively easy update.

Again, I know how opposed everyone is to my ideas. I also know the risks involved with what I'm doing but I'm big and ugly enough to make a careful decision and then live with the consequences.

Hi all,

As promised, I finally got around to building a complete in vitro plumbing setup to fairly test the performance of 3/8" pex against 1/2" pex in a controlled manner.

The test setup includes a hot and cold run for each size of pipe that is 24.5' in length. Each run has four 90 degree turns and is representative of the longest plumbing run in the entire house.

http://www.instructables.com/files/deriv/FWL/81YS/IRO1H43E/FWL81YSIRO1H43E.LARGE.jpg

A faucet and showerhead were tested for working pressure and flow rate for both the 3/8" and 1/2" pex piping runs. A set of PVC ball valves at the supply manifolds were used to select what size pipe was supplying the fixtures.

http://cdn.instructables.com/F51/8YGD/IRO1H3RN/F518YGDIRO1H3RN.LARGE.jpg

http://cdn.instructables.com/F5Q/ZH2S/IRO1H3RE/F5QZH2SIRO1H3RE.LARGE.jpg

In short, the results showed that the difference in pressure and flow rates between 3/8" and 1/2" were not statistically significant when using a mixture of hot and cold water. Both the shower head and faucet in 3/8" showed a 0.5% decrease in flow and 2.5% decrease in working pressure over the 1/2" pipe.

In fact, even with the 3/8" piping, the faucet and shower head flow rates of 5.89 liters per minute and 6.96 lpm, respectively, are too high to qualify for the high efficiency fixtures credit towards LEED certification... I'll have to deliberately have to add more resistance in the 3/8" plumbing run to bring those flow rates down.

I'll provide a link to the full write-up including the testing procedure and raw data when I have time to do it. Hopefully you'll find it interesting.

Cheers.

in your test. did you just turn on the sink and shower?

or did you turn on every fixture in the house?

as in, your wife/ life partner is washing dish's
your daughter is washing a load of clothes
your son and you are taking separate showers after playing basketball

this would be real life. for a family. that is how a plumbing system is engineered


fee free to plumb your house any way you wish. it is your house
have a goot day

It shouldn't matter, since every fixture is a separate branch from a larger manifold. Any drop in flow or pressure due to other fixtures being used is an issue with the capacity of the manifold or water supply, not the piping in each branch. Any issues would be felt the same by any size pipe.

In fact, during the testing, the supply manifold was able to hold a slightly higher working pressure when running 3/8" pex over 1/2". If anything, that would make the performance of a 3/8" pex manifold system better than 1/2" during multiple fixture use.

you do not get it, you keep saying pressure, pressure will remain constant because it is being pushed by a pump
volume, volume, volume not pressure





what is the volume of incoming water
what is the volume at each fixture with all fixtures flowing

Again, each fixture is on it's own small branch of a larger manifold. What one branch is doing does not affect the others as long as the manifold is able to keep up with the total demand. If multiple fixtures are drawing water and the manifold is not keeping up with that demand, that's a problem with the manifold or the municipal water supply, not one branch or the other.

If the main water supply or the manifold can't handle the demand then it's of no consequence what size pipe each individual branch is plumbed with.

The manifold is the only common denominator between each individual branch run. If a faucet on one branch is running and then somebody turns on a shower on another branch, it's the manifold that carries the extra load, not the faucet branch.

The working pressure of a piping system is anything but constant and it's affected by a multitude of factors. Perhaps you're talking about static pressure, which is only in effect when no water is flowing anywhere in the system.

I am finished with you, go argue with a wall

I'm sure you're a very highly skilled professional and incredibly knowledgeable in assembling piping systems, picking the correct fittings, components, compatible materials, installations, adjustments, interpreting codes and fixing plumbing problems. And because you follow the codes that are laid out for you, I'm sure all of your work is top notch and performs flawlessly.

But... and I sincerely mean no offense... when it comes to fluid dynamics (i.e. the science behind how it all works) you don't have a clue what you're talking about.

I'm sorry but it had to be said.

I don't care how many years you've been a plumber, you're not going to defy the laws of physics... you're just not.

please excuse my ignorant ass as i humbly...crawl into the room with this unworthy slip of paper in my trembling hand , to lay at the feet of the greatest
math guru since the three stooges..

are your runs matching this minimum size chart, allowed by chapter 6 of the 2015 upc plumbing code.

if yes, i was wrong your good to go.



what is the the runing psi at each faucet ?

Oh so now you ARE concerned with the working pressure of the faucet? Well let me tell you...


For cold only (cold tap fully open)...

1/2" pex: 37psi at the "manifold", 36psi at the fixture, 5.32 liters per minute

3/8" pex: 37psi at the "manifold", 34psi at the fixture, 5.03 liters per minute



For mixed (hot and cold both fully open)...

1/2" pex: 36psi at the "manifold", 36psi at the fixture, 5.93 liters per minute

3/8" pex: 36 psi at the manifold, 35psi at the fixture, 5.89 liters per minute



For the shower head (open to temperature limiting setting on mixing valve):

1/2" pex: 35psi at the "manifold", 35psi before the mixing valve, 19psi after the mixing valve, 7.05 liters per minute

3/8" pex: 35psi at the "manifold", 34psi before the mixing valve, 17psi after the mixing valve, 6.96 liters per minute


The "manifold" is the supply just before water enters the pex piping run.
"At the fixture" or "before the mixing valve" is immediately after the water leaves the pex piping run.
"After the mixing valve" is between the mixing valve and shower head.


As for the chart, I know that 20 years ago some bureaucrat somewhere said that I'm supposed to run 1/2" piping to my shower heads in some arbitrary imaginary test house somewhere in wonderland but why would I do that when I've tested on my own that the practice of doing it "just because" is complete horse****. I mean come on man, you're an American for Christ sake you guys don't stand for this kind of crap (and rightly so)... it's why you fought for your independence in the first place.

Numbers don't lie! The real world is not a one-size-fits-all solution.

I feel like you're getting very defensive and hostile towards me just for posting the results of my testing. I'm only doing it because I figured that a forum full of plumbers would find this interesting. I'm not trying to rag on anyone. Chill it a little.

does your system comply with the numbers I submitted ?


are you getting a minimum of 8 psi at each flowing fixture ?



plumbing inspectors do not give a damn about any BS stories.
it either complies or is red tagged. til it does comply.
the arbitrary numbers from 20 plus years age are still the numbers of today. math has not changed
as you so eloquently pointed out to me '''I don't care how many years you've been a plumber, you're not going to defy the laws of physics.''' same goes for these old ass plumbing laws and the math the engineers used to arrive at these numbers.

look, i am happy as **** you went thru all of this, i am sure you learned a lot and enjoyed it every minute.
but in reality, we have a code that we must use, i will not endorse anything that does not meet or exceed this code
dont you think we all have come up with ideas and practices that we are convinced are better than the code ?
come on man, I have been slinging pipe for over 35 years, hell yes i know stuff that i think is way better.
but, when it comes down to installing. it is done by the code book

talk to your inspector, show him your findings ask him for a variance, hell, he dont care
its your home. he will issue a variance with a written warning or recommendation, a cya type deal
but. here is the kicker. people add on to homes, it is a huge industry.
if you knowingly install undersized piping. you must disclose that fact when you sell
someone is going to open a wall one day and be pissed !!

What our disagreement boils down to then, is not whether or not this plumbing system will work and provide virtually the same performance as the same configuration done in 1/2" pex, it's whether or not the code book should be blindly followed even though it's not a good fit for this situation.

My problem with the table is that it has absolutely no context. The pipe sizes seem to be made up out of nowhere. There's no consideration given to the length of the run, number of turns, flow rate of the fixtures, etc. It doesn't even discriminate between two different tub sizes listed in the same table. In a perfect world, it shouldn't have to be used to dictate every piping run, everywhere. I think it's old and outdated and was probably made when fixtures and appliances used a lot more water than the do today.

You as a plumber should absolutely follow the code since your license depends on it. However, there are no inspectors whatsoever where I'm building. It's a small town rural area in the middle of nowhere. This past weekend I framed up the first three exterior walls and yet I've had the occupancy permit since May. I can do whatever I want with the plumbing.

Hopefully someday the code books will be updated to allow more appropriate pipe sizes to be used. They can use my house for a case study if they wish. Like everything, somebody has to be the first one to do it.

As for renovations, all rooms in the house with a plumbing fixture share a common wall with the utility room. It should be very easy to create a new branch run from the manifold to anywhere in the house. I was also planning to run a couple of stubs to each end of the house to allow for easy expansion in the future.

Hey frodo you are talking to a wall I think now everyone understands why I get so frustrated when some asked for help then tries to re write how things work. Let him screw it up it will come back in the end the he will pay out the ass for one of us to fix it. College degree in math don't make you a plumber or smart. And this comes from a high school drop out making six figures a year. You can't fix stupid. A degree don't give you common sense

A degree certainly does not give you common sense but neither does being a plumber or making a six figure salary a year, apparently.

I'm sure you're a great plumber and society has benefited greatly from that. However, being so quick to throw out scientific data and empirical evidence in favor of or own stubborn beliefs or blind faith in some piece of paper, society has also benefited greatly from you NOT being a doctor, lawyer, scientist or engineer.

How else would we have moved out of the stone age?

Being willing and able to question the world around you, keeping an open mind, thinking outside the box and challenging the status quo are not signs of stupidity or lack of common sense.

Don't try to re invent the wheel it is round for a reason. You are asking for advice use it or don't. But I deal with people all day long that throw a college education around like it has any weight in the world and all it tells me is that you had to spend money for someone to teach you how to think. So take your damn degree and figure it out. But apparently you need some one else to think for you again and do all the leg work. Man that sounds like money well spent on that higher education

The irony in the things you say is rich, so very rich.

https://youtu.be/9yoQgAQOALc

!!!OMGAWD!!!

Will the powers that be please lock this thread???

Why when it's getting so good. It's like the plumbing version of the young and the restless....coded and plumbless. I've had a few laughs out of it. Just reminded me of when I was teaching my helper and he questioned everything and was determined to get the code changed because it did not make any sense to him.. all I could say was good luck and let me know before the new book comes out.

HIJACKED

FRODOS MUSIC THREAD




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