Drain piping for washer???


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Old 03-05-07, 09:08 AM
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Angry Drain piping for washer???

My friend needs to install a washing machine in the closet on the first floor. The current drain is located in the crawl space under the floor of the bathroom next to the closet.

The washer drain adaptor will be installed between the studs with cold and hot water supply pipes and the ABS drain pipe in the middle. The 2" drain will make a turn under the subfloor into the crawl space and hooked up to a 2" pipe that is the drain from the bathroom's vanity sink, using a 45 degree Y section. A P trap will be installed before entering the Y section.
The question is.

1. The vanity sink drain has a venting to the roof already. Is it OK to share that venting pipe? Here is the setting: from left to right, the venting pipe, vanity sink drain, then washer drain, then main sewage drain.

2. Is it necessary to install a clean stop cap at the end of the Y section since you have to cut open the pipe anyway?

3. Will the P trap slow down the sucking power of washer drain? He is worrying about the spilling over if water goes away too slowly.

Wall is already open. He cannot write English, but waiting for suggestions. Thank you very much for your input.
 
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Old 03-05-07, 09:53 AM
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The washer P-trap should be at the bottom of the washer stand pipe, that way you ensure the vertical column of water maintains a good flow of water through the trap and things don't slow down. The UPC code (code for my area) for standpipe height is 18-30" min/max, but I really don't see that taller is bad if you have to go that way (P-trap at the bottom of the standpipe in the crawlspace?).

Ideally, after the washer P-trap, the horizontal drain line should have a wye inserted and a vent line tied into the bath vent. That would be ideal. Otherwise, what you describe would be doing a 'wet vent' and that is trickier. Both the washer and bath pipes should be oversized to accomadate the wet vent setup. If you go with the wet vent and don't oversize the pipes, you might get by using a Studor vent or air admitance valve on the washer drain (after the p-trap). This keeps the drain water from sucking the water out of the washer and bath P-traps which is a safety issue!

Re: Is it necessary to install a clean stop cap at the end of the Y section since you have to cut open the pipe anyway? - I'm not sure what this means.

You say the bathroom uses a 2" drain, and the washer will also; 2" is a normal size for bathroom sink and washer drains so there should be no problem carrying the drainwater away as long as the proper slopes are maintained.

Hope this helps.
 
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Old 03-05-07, 10:33 AM
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Thank you , Formula for your prompt response.

The standpipe height (from under the adaptor box) will be 42". That is the height of the washing machine. He can put the P trap as close to the bottom of the standpipe as possible, but not immediate under it, because there is a concrete block wall dividing the two areas under bath and closet. An elbow will be used between the cold and hot pipes to lead the drain to the other side of the wall. (you see cold, hot water pipe and the drain stand side by side and there is no space to install a P between studs.) The P can be put just one foot away right after it turned horizontally into the crawspace. It will go 2 feet further to be elbowed into the wye. The total new drain length will be a bit more than 3 feet only. So I do not see a big difference of putting P trap at the beginning or end of the new horizontal pipe. And there is enough pitch.

I like your term of wet vent. It is a small house, the shower drain is another branch of the main sewer pipe and has its own venting shared with the kitchen sink drain. The bathroom sink (small one) drain will not generate much waste water while you operate the washer. This is the shortest route.

The cap I meant is "standpipe cap." that people used to open the pipe to clean and remove clogs.

I do not know if code in NJ allows to install a stador vent. Is it also called AAV?

Thank you again.
 

Last edited by lzhang; 03-05-07 at 11:03 AM.
  #4  
Old 03-06-07, 01:29 PM
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Yes, I knew a Studor vent as an air admitance valve first, only learning the Studor name later.

Glad you like the 'wet venting terminology, but it's not mine, it's a plumber's term (and I'm not a plumber). Some local building codes allow wet venting and some don't. Basically to wet vent, you use one size larger pipe to allow the water/waste to flow along the bottom of the pipe and the vent air to flow along the top. For your 2" washer drain, you might have to go to 3" pipe to be legal (do they make 2 1/2" pipe"?), which would probably be hard for you to install in the tight quarters I'm imagining you have.

All in all, I think you will have a good installation helping your friend with the washing machine hoopup. Good luck!
 
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Old 03-06-07, 08:05 PM
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Thank you, formula, I noticed you just completed a lovely huge new house. You should be the master of a bit everything. We will try and give you guys some feed back.
 
 

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