I want to install a wall box with a standpipe drain for my washing machine. I'm trying to figure out how to plumb the drain line. Here are my questions:
- Should I use 2" drain lines?
- Do I need a trap (I'm assuming yes)?
- Do I need a vent (I'm 32 inches or less from the stack)?
- If I do need a vent, where should this connect to the drain?
- How far does the vertical part of the standpipe need to go (do I need to put the trap under the floor)?
- Can I tap into an existing sink drain (1 -1/2")?

All of my drain pipes are ABS

Thanks.

jonboy99

Additional question: When I tie into the stack, will I need to put in couplings above and below my new tee (where the new drain comes in) to allow me the movement I need to get the tee in place? I'm on the upper level of my home, but i have 2 tee's above where I'll be tying in (one for a sink drain and another for the bathtub vent). My install location backs up to a bathroom.

doug238

it would be difficult to advise about this installation. are you going to be flushing the washing machine by anything? a washing machine can pull water out of traps by suction if not on a properly vented line. the washer connection must be a 2" trap on a minimum 2" line and i suggest a minimum standpipe height of 18". you are close enough to not need additional venting unless a toilet is above your connection. yes you need a trap. using no hub couplings would make the new sanitary tee fit without moving the pipe up or down during the tie in.

speedball1

1) Should I use 2" drain lines?
Yes, with todays more powerful pumps 1 1/2" won't carry the volume produced away.
2) Do I need a trap (I'm assuming yes)?
You assumed correct
3) Do I need a vent (I'm 32 inches or less from the stack)?
If there's a major fixture that discharges from above then yes you will need a vent. If it's a dry vent stack then no you wouldn't.
4) If I do need a vent, where should this connect to the drain?
Downstream from the trap and before it connects to the stack.
5)How far does the vertical part of the standpipe need to go (do I need to put the trap under the floor)?
the trap does not have to go under the floor. Dougs 18" standpipe falls woefully short of the required length. We place our trap as close to the floor as possible and make our stand pipes 2 inches over the flood rim of the washer. This works out to 30 something inches. You're assured of a back up with a 18" stand pipe.
6)When I tie into the stack, will I need to put in couplings above and below my new tee (where the new drain comes in) to allow me the movement I need to get the tee in place?
Doug was correct when he recomended two No-Hub Couplings. When you make the cuts in the stack don't forget to prop the stack up from falling until you get the sanitary tee in place. Good luck, tom

doug238

woefully short? SBCC STANDARD PLUMBING CODE
PAGE 63 802.4 STANDPIPES
standpipes shall be individually trapped. standpipes shall extend a minimum of 18" [457 mm] and a maximum of 42" [1066 mm] above the trap. access shall be provided to all standpipe traps and drains for rodding.
tom, as you know, many plumbers have a personal preference on heights and distances. i do not particularily like an 18" standpipe but in a location where i cannot get more i will use it. 18" is not woefully short of code requirement, it is woefully short of your personal preference. please check your local codebook before you make a statement about someone not being code compliant.

speedball1

I don't need a code book to tell me that a 18" standpipe will over flow. Experience and common sense tells me that. Who knows when that code was written. It certainty doesn't address todays more powerful washer pumps. I can see suds blowing back every time from a 18" standpipe.

"please check your local codebook before you make a statement about someone not being code compliant."

I didn't say it wasn't code compliment. I said it flat wouldn't work without backing up. Just go back and revieww the back-up complaints we get from askers with standpipes that are over 18" in length that have had the drain lines snaked and are still backing up.. It's a no-brainer.
Doug, codes aren't written in stone. Sometimes you have to use good sense in applying them. Since you seem determined to challange every one of my answers it's time to let us to know just who you are and what your qualifications are. One more time i'm going to ask. Are you a licensed plumber and how long haver you been out in the field? What do you do? Rough ins? Tub sets? trim outs? Service calls? Come on Doug, you've been very vocal with your criticisms and comments. Let us know a little about you? Regards, Tom

doug238

tom, i have practical experience in all phases of residential plumbing installation including abs, pvc, cast iron, cpvc, copper, poly butylene, pex, galvanized pipe,and black iron pipe in slabs, off grade crawl space, basements, multistory and multi family housing. i also have practical experience in commercial plumbing to a slightly lesser degree and i also have practical experience in service work on all of the above. and i also am licensed.
and i have seen many 18" standpipes not back up.

jonboy99

Thank you for your expert help! I really appreciate your time. Since this is an upper level and I'll be tying in above the toilet, it doesn't sound like I need a vent. I'm installing a smaller front-loading washer and it specifies a max 30" standpipe height. According to speedball1, It sounds like taller is better, but I don't know what issues I'll run into if it is more than 30". If there are thoughts on this topic, please let me know...

Now, I just have to figure out what a "no hub coupling" looks like (now that I know what to call it, I'm sure I can figure it out).

doug238

taller is better. i was only giving minimum code requirements. a fernco couple [coupling] is simply a back rubber sleeve with 2 hose clamps on each end.
if your traps on the lower floors are dry, remember these posts about venting and vacuum.

speedball1

These are No-Hub Coulpings ,(see image). I prefer them over Fernco neoprene couplings because they are a more ridged connection. If you're discharging the washer into a vent stack that services the downstairs toilet it's doubtful that you will have to vent it, but as Doug suggested If you hear "gurgling" out of the downstairs traps when the washer discharges then vent the washer.
When we install a stand pipe or a washer box we try to keep the washer trap as close to the floor as possible and terminate the stand pipe about 2 inches over the flood rim of the washer. And you will not run into any issures if the standpipe exceeds 30 inches. Good luck, Tom