shower/tub combo to shower conversion

Hi everyone,
first time here, and of course I need some help to figure out a plumbing issue.
I am converting a bath/tub enclosure to a walk-in shower type.
The rough-ins inspection has been done and all approved, but...the inspector recommended to consider changing the 1.5 inch drain pipe to a 2 inch one.

It would be really a PITA - he said I might be able to have enough flow/drainage, but might have also some slow drainage issues.

The run is properly vented btw

So, my questions are:
- can I indeed leave that existing pipe alone? the water pressure is standard, and the shower pan 3x5 feet will have the drain at the center or about 6 inches from return wall, and will be tiled with sealed stone pebbles (increased slope)
If, indeed this pipe sizing is know to cause a lot of issues with showers, I rather solve it now
- assuming that I keep the 1.5 inch drain pipe - how can and should I adapt the 2 inch drain to the 1-1/2 pipe? - yes I will install a P trap and the pipe runs parallel to return wall so needs a 90 degree elbow in the run for a center pan drain.
Thanks in advance for your help and advice

Phil

...am I asking a "taboo" question or something else wrong?
I mean, I was not expecting to have flood of answers, but neither having no reply of any kind despite over 100 views.

oh well...

been busy, gotta make that dollah bill yo !!!

you mot likely have a 2'' trap under the tub. and 2'' pipe going to the trap

remove tub and cut disgard the old trap.

add new pipe and trap to the showere drain location

on your shower/tub valve raise the valve up and center it

either cap the tub spout pipe, or. install the spout about 18'' off the floor of the shower floor

to rinse feet, was dog, fill a mop bucket

Hi Frodo
glad to hear that you are getting more than enough business.

Actually I already removed the shower/bath combo fiberglass thingy - and in 1994, code allowed for a tub/shower combo to run a 1-1/2 inch line. So, that's exactly what I have
However, the line runs under the floor for another 7 feet or so, and I believe it joins with the drain run from another tub/shower combo from the adjacent bath.Then goes down to the crawl space - it's a split floor house, and baths are located on the second floor btw (the crawlspace is actually walk-able +/- 6 feet.
The shower head I will be using has a 2.2 gpm max output - shower pan will be a 3x5 tiled with flat top pebbles and was planing to build it with the Kerdi system. hence my dilemma/question.
Kerdi drain requires a 2" pipe.
So, I either change the line to 2 inches, or place an adapter just after the drain (before P-trap and vertically, if indeed have room) or don't use Kerdi at all, and have to look for another system.
I have not purchase anything for the pan yet, as I am debating with this issue, and really would appreciate any input from the experienced pros here

Read somewhere else, that similar flow rates usually don't cause issues on smaller diameter pipe drains, but if you can believe in everything you read on the internet....

code calls for a tub/shower to be minimum 1 1/2

you are switching to a shower unit, not a tub/shower unit, minimum code is 2''

you will have to follow the 1 1/2 back to where it ties in.

change out THAT fitting to a 2'' fitting

install a new 2'' line, that can not be more than 5' long with out installing another vent

frodo said:

code calls for a tub/shower to be minimum 1 1/2

you are switching to a shower unit, not a tub/shower unit, minimum code is 2''

you will have to follow the 1 1/2 back to where it ties in.

change out THAT fitting to a 2'' fitting

install a new 2'' line, that can not be more than 5' long with out installing another vent

Click to expand...

Thanks once again Frodo
I got a rough-in inspection done already - the inspector mention that, but said it was acceptable - he said too, it's possible to have minor some flow issues. However, once he was told about the shower flow/setup, he said that was less likely.
For me still means "you want a headache now or later?"
I can hook up to another vent once pass 5 feet, but changing the 1-1/2 run, probably means that I have to open another wall - to the in-between level, extract this length of pipe all he way to the drop, enlarge the existing holes in the joist and then place the new 2 inch run - will be a 8 footer piece (yes, it's perpendicular to the floor joists).
I want to do the right thing, but....all liabilities on me and no one else, what would someone else could/should do in a similar situation as mine?
Take a chance, or take another week to get it done? (mind that technically it's approved by the inspector, scary as that might be or not LOL)

edit:
would two 45 degrese elbows allow for a better flow instead of a 90 degrees one? - it was the original setup before I cut off and tap the pipe
attached is a picture of the rough-in (not completed when taken) and a shower layout drawing in pdf



View attachment bathroom-06-29.pdf

how far back does that 1/1/2 run ?

,,,,,,,,,,,,,,,,,,

frodo said:

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Click to expand...

Hi Frodo,
yes, it's not there ...but it will be once I determine which setup I will use.
-sort of in between the two suds where the water lines go up
Kerdi kit places the drain either in the center or 10 inches offset from center.
a trough drain would allow me to keep the run without any turns, as it would be placed near the return wall edge.
if not going for either option, then it will be whatever fits the best, as the pan will have to be custom made.

what you see in the picture it's a slight longer run from before, and yes, I had to cut off the P-trap and elbow and run past a bit the new vertical connection.
The vent was about 3 inches or so from the framing thru the floor (inside the shower/tub shell) - had to re-route it, and chose to place a longer run after the Y for extra flexibility later when comes time to choose where to place the drain.
the total room width is 7 feet 8 inches, so I estimate that the drop and next vent are 5 feet or a bit less from the vent you see in the picture - it goes to the left, and might join with the other drain run - sort of behind it, and then down to the crawlspace (there is only one vertical run aligning with it)

...and yes the Y is not placed correctly in the picture - neither was glued at the time. This was just a 'does it fit' for me and "it's it legal?' question to the inspector.

if, you are building your own pan in place, just hany the trap on the pipe and swing it out

slope the floor to the trap/drain


NOTE" youu do what you want, but, if you leave the 1 1/2 drain in the floor, you WILL
be taking a shower while wading in 4'' of water

frodo said:

if, you are building your own pan in place, just hany the trap on the pipe and swing it out

slope the floor to the trap/drain


NOTE" youu do what you want, but, if you leave the 1 1/2 drain in the floor, you WILL
be taking a shower while wading in 4'' of water

Click to expand...

Thanks Frodo.

I agree and hate to say it - trying to make my case to blow the budget and finalizing time a bit with this extra requirement....

wish I could tap onto the existing 2 inch drain that runs behind this 1-1/2", but probably aside illegal, would just bring more issues (as if I need more)

a very silly question follows:
(my gut feeling says no, but I have to hear a no)
- what if, I uncover the floor along the 1-1/2" run, all the way to where I assume it connects to the main run and vertical drop, and instead of a full length of pipe, I use small sections of maybe 2 feet or more (depending of ability of wiggle it in a new widen hole in the floor joist) all with black glue and connectors to make the run from new drain location till existing 2 or 4 inch drain pipe?
what I am trying to do is avoid having to open a wall in order to remove the existing 1-1/2" run....and cutting the floor joists to remove and then reinforce it with two new short 2x6 in each side seems worst and not talking about cutting the whole way down - just to bottom of existing hole for the pipe run (hope that this description makes sense - I can post a quick sketch for clarification if needed)


update: called my local permit/inspector office - they are sending an inspector for a plumbing consultation, to see what I have there and how to solve the problem the best way possible.
They will approve the 1-1/2" drain ( well, it has already). recommend a 90 degrees sweep or two 45s to make the turn smoother, and even the reducer from 2 to 1.5 and the drain flange when placed vertically (and before P-trap)
regarding floor joists, the structural says that would be too much of notching - 5 to 6 2x8 joist - so, the other recommended solution is indeed enlarge the holes and wiggle a 2 inch piece as long as possible and glue all together with connectors and black glue to make the run.

So, this consultation will be to confirm if indeed this can be done, or if there is another way and give me some advice how to get it done - for now I have to open the floor all way to the wall, so we can see what's under

I will update the findings once it gets approved

i frequently install short pipes between studs so that i do not butcher the structure

only caution. make double damn sure your pipe has fall and no bellies.

when i mark holes for a drain to drill. i move my center mark up or down depends

frodo said:

i frequently install short pipes between studs so that i do not butcher the structure

only caution. make double damn sure your pipe has fall and no bellies.

when i mark holes for a drain to drill. i move my center mark up or down depends

Click to expand...

very good point - actually I will dry to induce a small down pitch after the turn if I can.
not sure how the whole whole system gets together at the vertical drop, but I anticipate having to redo the connections....

IPC code allows 1 1/2" to shower drains now. And that will easily handle the flow from a single showerhead. But over time, you will get hair and crud buildup in the trap and horizontal drain, bigger pipe will take a lot longer to clog than will smaller pipe. I would try to change it to 2" if it were my house.

I would also be very concerned about those Sharkbyte fittings on the water pipe. Too many failures on those for my liking.

phishfood said:

IPC code allows 1 1/2" to shower drains now. And that will easily handle the flow from a single showerhead. But over time, you will get hair and crud buildup in the trap and horizontal drain, bigger pipe will take a lot longer to clog than will smaller pipe. I would try to change it to 2" if it were my house.

I would also be very concerned about those Sharkbyte fittings on the water pipe. Too many failures on those for my liking.

Click to expand...

Thanks for you feedback Phishfood - good to know, and that explains a lot, and yes, almost positive that I will change for a 2 inches pipe

I am siting uniform plumbing code not International plumbing code

I believe that is the mix up.

what state are you in, that will tell us which code you are under

frodo said:

I am siting uniform plumbing code not International plumbing code

I believe that is the mix up.

what state are you in, that will tell us which code you are under

Click to expand...

Oregon - city of Hillsboro 97123

Oregon specialty code

table 10-1 2'' trap maximum 60'' trap arm from vent

table 7-3 shower with 1 head 2'' minimum trap

your drain size is 2'' minimum according to oregon code

frodo said:

Oregon specialty code

table 10-1 2'' trap maximum 60'' trap arm from vent

table 7-3 shower with 1 head 2'' minimum trap

your drain size is 2'' minimum according to oregon code

Click to expand...

Thanks once again Frodo,
the consultation went very well actually - yes, he confirm pretty much everything you said, but, they have also the ability of making a judgment based on their experience - in my case there are a few things that allow an exception. The 1-1/2 run actually connects to the 2 inch run about 30 inches after a turn. He advises to hook a sweep 90 and try to install a 2 inch p-trap followed by a bushing to 1-1/2 or if the space becomes too tight just use n adapter on after the drain. worst case scenario, just the sweep should be enough to keep out of problems, but to remain proactive with hair clogs.

my next big task now is to figure out the hook up of the kerdi drain to either p-trap size - as I have no easy bottom access - u-tube videos from kerdi here I come......

you get one of these