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Stephen S. 04-21-2010 02:01 PM

Tub and Shower drains
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This is my first time doing a bathroom remodel so I have lots of questions. Please bear with me. I'll put up the first few for now ...

I am going to put a left-hand drained whirlpool to where the center-drain fiberglass shower was so I'll need to move the drain.

1) How to determine if the subfloor is strong enough to support the tub (Kohler Archer Whirlpool) + mortar bed? The subfloor was constructed with 2x9? (exact measurement 1.5"x9") and distance is 16" apart.

The overflow assembly came in PVC, and my drain pipes are ABS, I'll connect different materials together by using rubber coupler after the PVC P trap.

2) A big opening (similar to the one at center drain) at the 2x9 so the tub P trap can be tied to the existing pipe using a Tee (depends on Q#3) Is there any problem cutting such a big hole (indicate by red)? I'll repair the existing cutout by sistering the center 2x9.

3) I will put in a new shower. Can I connect the shower drain pipe to the existing drain as shown in the picture (share with the tub) ?

4) P trap should always be placed right under the drain hole, correct ?

Thank you.

Jim F 04-21-2010 08:13 PM

I am doing something similar but having to stop so much it's frustrating. I'm sure the pros will weigh in here but one thing I see is the black 6 ft section where you are tying the shower drain to the tub looks like it may need a vent closer to the shower drain. Or is there one out of sight?

Stephen S. 04-21-2010 10:33 PM

There's no vent near the shower drain at the moment since the shower is an add-on. Can I tie the drain pipe to the same drain pipe as the tub drain and share the vent as well ? If not then I'll need to run a vent pipe up the roof ... Any pro please advise?

oh'mike 04-21-2010 11:09 PM

Showers need a 2" drain--If the black piping is 2" you should be O.K. run a vent pipe near the new shower--join it to the vent in the attic.--Mike---

Nice pictures--thanks

Alan 04-21-2010 11:14 PM

I'm not really sure what your local code is, but oregon requires each fixture to have it's own vent, excluding wet-venting, considering you're in a ceiling/subfloor assembly, you don't really have the space to wet-vent.

Shower drain requires 2" pipe, and the vent can be 1-1/2" and must be within 5 feet of the trap outlet.

Tub drains require 1-1/2" pipe and the vent can be 1-1/2" and must be withing 3-1/2 feet of the trap outlet. Tub drain can be upsized to 2" and then can have the same 5 foot requirement as the shower drain. (use a 2" trap with a 2x1-1/2" bushing in the inlet of the trap if you need to do this)

Also keep in mind you are allowed only 90* change of direction between the vent and the trap outlet.

Alan 04-21-2010 11:15 PM

P.S. for your shower trap hole, if you can line it up just right (should be no big deal) you should only need a 3" round hole.

The notch where the shower trap is going currently looks like it's just blocking, not a support joist. That should be fine, so if you need to notch the other one it should be no big deal.

Alan 04-21-2010 11:22 PM

As for support, we leave that kind of thing to the carpenters... figure the volume of your tub in gallons x 8.3 lbs per gallon of water...

plus 100 lbs give or take for the tub if it's jetted, maybe a third less for a soaker.

add 80 lbs of mortar, and any framing needed underneath to elevate the tub if you're doing something like that.

post the result plus your current framing in the building/construction section.

P.S. your tub specs SHOULD give you the weight of the unit itself.

Stephen S. 04-22-2010 08:57 PM

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Thank you Alan ! In this case I'll need to make a new vent through the roof as the existing stack is 8 feet away. Could you explain only 90* change of direction between the vent and the trap outlet ? Can I put the shower vent along the pipe as indicated in picture ? The horizontal section of the vent will slope towards the drain.

One more question, I know I'll need to drop the drain pipe 1/4" every 1 foot run ... by the time the new shower drain pipe (~6 feet) reach the old drain pipe at green circle area, the new one will be an inch or so lower than the old one. Can I connect them together by sloping back upward there ? Thanks.

Jim F 04-22-2010 10:20 PM

To reiterate what O'Mike said above, you only need to punch another vent hole in your roof if that is your best or only route. The new vent can tee in horizontally with your preexisting vent in the attic space or there are other options.

Alan 04-23-2010 12:27 AM

No. Unfortunately your vent may not travel horizontally until it is 6" above the flood level rim of the fixture. In this case you need to hit the wall first, and then travel toward the center of the shower so you can put a p-trap and tailpiece on.

Is it going to be a custom shower or a fiberglass stall? Make sure you have the drain assembly in-hand before figuring your elevation for your run. You don't want to end up with the p-trap too high to where there's no room between inlet and drain assembly.

Also : going back uphill to connect? No. Is there any way to get a fitting a little lower? This is going to be a bigger problem since you have to run your drain to the wall, now you're travelling a longer distance. Is there a wall downstairs that is any closer? Is your house on a slab? Can you take a picture of the connection that you're going to make?

Stephen S. 04-23-2010 02:02 AM

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Thank you again! I get what you mean now. There's another level downstairs without any plumbing I can connect to unfortunately. All plumbings are on the left wall.

It is going to be a custom shower with Schluter shower system/drain. I'd wait for all the hardware to arrive before doing any actual drilling. I'll take picture once I dry fit all together.

Here's what my revised plan is ...
green line shows the toilet drain,
red line shows new 2" shower drain which can be tied to this pipe (probably sink drain pipe?) with a tee,
orange line shows 1.5" vent (Is there a distance limit if tying to the existing vent assembly purple lines that is 8' away in the attic ?). What do you think ?

Alan 04-23-2010 10:07 AM

It looks good now. The only problem I see is that you say you will tie in with a tee. Use a wye or a combination wye/45* bend to tie into drainage lines.

I believe the max distance horizontal a 1-1/2" vent can travel is 30 feet. 8 feet is no big deal. Just make sure your vent is either perfectly FLAT or grades back to drain.

You may need to take out a little more subfloor....

Your drain should be on the outside of the shower wall so that you have room to put a long sweep 90* and a 2x1-1/2" santee for the vent fitting.

Also make sure you don't put your vent in the same stud bay where the valve is going to be.

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