# Reduce shower drain size?



## kripes (Oct 8, 2009)

The kerdi drain I'm installing is 2" and the existing drain pipes are 1.5". The vent is about 8" away from where the p-trap meets the main drain run. The vent is 1.5" of course.

I've been doing some reading and people talk about replacing the drain line with 2" pipes but that means ripping up flooring / carpeting in other rooms so I don't see that being at all feasible. I think my options are:

Feed the 2" drain directly to a 1.5" reducer and then use 1.5" pipe from there, keeping the choke point at the drain.

2" drain leads to a 2" p-trap and just after the p-trap reduce to 1.5". Note I'm going to need a 45" elbow at or near the p-trap as the drain pipe leads off-centre.

Notes:
I live in Ontario
I did not install fixtures that increase the water output from before.
The home is about 30 years old


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## oh'mike (Sep 18, 2009)

I believe that doing that is a code violation--also a risk---How long is the drain ?

I've never cut that corner---but always found a way to correct the undersized pipe.

Let's see what the plumbers have to say---


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## ddawg16 (Aug 15, 2011)

I just went through this....showers have to be 2"...but a bath tub can be 1.5". 

Reason....if the drain on a tub gets blocked....the tub holds the water. But with a shower (not tube/shower), you don't have that big volume buffer. The water needs to drain in real time.


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## kripes (Oct 8, 2009)

I can't tell how long it is... It goes about three feet past the vent (under the closet) then makes a right through a joist...


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## ben's plumbing (Oct 6, 2011)

kripes said:


> I can't tell how long it is... It goes about three feet past the vent (under the closet) then makes a right through a joist...


 while it may be a p.i.a. you really have to keep the trap at 2" for code. will 1 1/2 work yes ...will it pass inspection no .. you can now decide which way to go ....


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## kripes (Oct 8, 2009)

ben's plumbing said:


> while it may be a p.i.a. you really have to keep the trap at 2" for code. will 1 1/2 work yes ...will it pass inspection no .. you can now decide which way to go ....


I can fit a 2" trap and then taper to 1 1/2". No PITA for me. So it sounds like you're suggesting I go with my 2nd plan. 


Neither way is "code" but ...as long as it drains I'm happy


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## kripes (Oct 8, 2009)

Ran into my plumber last night and he suggested inserting a 2" reducing bushing.


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## ben's plumbing (Oct 6, 2011)

there is another idea...is it code no ...will it pass inspection no..will 1 1/2 work yes ..you can now decide how to proceed...


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## Ghostmaker (Mar 2, 2013)

ben's plumbing said:


> there is another idea...is it code no ...will it pass inspection no..will 1 1/2 work yes ..you can now decide how to proceed...



It will work with a single shower head. But the drain reduction will be prone to blocking.
Also I'm sure this work requires permits and inspections in Canada.


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## Yodaman (Mar 9, 2015)

Ghostmaker said:


> But the drain reduction will be prone to blocking.


Like ghost said the reduction will be prone to clog. But if you are going to disregard the code and do it anyway, I would suggest putting the reduction in a vertical drop and avoid a horizontal line reduction at all cost. Will there be any accessible clean outs or is it all getting tucked under the floor when finished?


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## kripes (Oct 8, 2009)

I read the permit rules for my town and I don't believe the work I'm doing is large enough to warrant a permit. 
There will be no accessible cleanouts; it'll be under a floor under a shower pan under some tile in the end.
The old 30 year old 1.5" drain was starting to suffer because of calcium buildup, but after some dran-o it would work fine for a couple months.
I don't want to come across as argumentative but I struggle with the notion that a 1.5" drain will no longer be sufficient when I'm still coping with the same water output as before.
I get the undertones that I should be running 2" to the vertical stack, but I have no guarantees that it's even under the closet.


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## Yodaman (Mar 9, 2015)

kripes said:


> 1.5" drain was starting to suffer because of calcium buildup, but after some dran-o it would work fine for a couple months.
> I don't want to come across as argumentative but I struggle with the notion that a 1.5" drain will no longer be sufficient when I'm still coping with the same water output as before.
> I get the undertones that I should be running 2" to the vertical stack, but I have no guarantees that it's even under the closet.


Since you were having trouble with the old line, kinda says that something could be better.

You are getting the undertone because 2" shower drains are the current code. And they want you to plumb it to code. And it will work better.


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## ben's plumbing (Oct 6, 2011)

you ask what you need to do...according to code ...showers need 2" pipe and trap.... over the yrs in the plumbing business i have seen 1.5 pipe drain washers and showers. which require 2" and drain for yrs with no problem ......when we are contracted for work we bring all the plumbing up to code that will pass an inspection...its a must when you file a permit ..


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## kripes (Oct 8, 2009)

So you guys would keep ripping up carpet and subfloor until you found the stack? The stack is 2" for sure?


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## oh'mike (Sep 18, 2009)

The 'stack' is likely to be 3"---however--it is also likely that the shower drain meets up with a sink drain and becomes 2" after that.

You won't know until you open up the floor (or the ceiling below)


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## Yodaman (Mar 9, 2015)

any way to drop a new 2" line down thru a near by wall and tie it in to the main somewhere below?


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## Ghostmaker (Mar 2, 2013)

I would suggest you actually call the code officials. In my area touching a drain and installing a shower all requires permits and inspections. The shower valve itself requires it be pressure balance and temperature controlled to prevent scalding.


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## ben's plumbing (Oct 6, 2011)

we are going to keep telling you the requirements for the code...its what we have to do ...you said if it drains your happy. even though its not code...lets put this one to sleep....:yes::yes:


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## kripes (Oct 8, 2009)

Thanks. Need to think about it


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