Washing machine drain plumbing

[Stephen Tashiro]

In plumbing for a washing machine drain, is there a limit on how high the outlet of the p-trap can be relative to the outlet of the drain that's built into the base of the washing machine?

I'm only familiar with situations where the p-trap for the drain is in a crawlspace and far below the outlet on the washer. Now I need to plumb a washer that sits on a concrete slab so it drains through an exterior wall.

[Tom M King]

I posted a thread with the code picture in it a while back. I had to change one in a rental house that wasn't working because it was plumbed wrong with too small of a pipe. I'll see if I can find a link to that thread. There is a max for the drop to the trap. Too high and it will flush the water out of the trap.

edited to add: I remembered it wrong. It's in with this thread, but it was another forums that I posted the code diagram on. I'll find it. The pictures of my fix in that thread covered about the only way I could do it. The drop to the trap was 28", so within code.

https://sawmillcreek.org/showthread.php?305208-Washing-machine-shut-off-valve-wall-mounted-not-Sharkbyte&highlight=washing+machine+drain

https://global.discourse-cdn.com/internachi/original/3X/9/5/95e96f0e8f592c404318f190f2b33eb5bda16b91.jpeg

[Bruce Wrenn]

Building inspectors here require trap to be as close as possible to floor level, and stand pipe to be at least 43" off finished floor.

[Stephen Tashiro]

My concern is about the height of the trap outlet (the pipe through the wall) above (or below) the drain outlet on the washing machine. Does this matter at all?

If the pipe through the wall is set 6 inches above floor level, it would be a little below the level of the drain outlet on my washer. (- the outlet built into the washer, not the end of the rubber hose that goes up from that outlet.) Is that why code wants the trap near the floor?

[Jim Becker]

The trap for our laundry room is under the floor in the basement ceiling joist area.

[Lee Schierer]

If the pipe through the wall is set 6 inches above floor level, it would be a little below the level of the drain outlet on my washer. (- the outlet built into the washer, not the end of the rubber hose that goes up from that outlet.) Is that why code wants the trap near the floor?

I built a box that raised our washer ~15" off the floor so that my wife doesn't have to bend over so far to get hings out of the basket to load it and can easily look inside to capture loose socks before they get lost. Raising the washer would solve your drain height problem. The washer installation instructions should have a diagram similar to the one posted above for the drain piping set up.

[Cameron Wood]

My concern is about the height of the trap outlet (the pipe through the wall) above (or below) the drain outlet on the washing machine. Does this matter at all?

If the pipe through the wall is set 6 inches above floor level, it would be a little below the level of the drain outlet on my washer. (- the outlet built into the washer, not the end of the rubber hose that goes up from that outlet.) Is that why code wants the trap near the floor?



The outlet of the washer is not a factor- the discharge water is pumped out. The trap is near the floor so that there is enough stand pipe to handle the water. If water backs up out of the standpipe, a fix is to throttle the drain hose with a hose clamp, so the water comes out slower.

[Maurice Mcmurry]

Toms diagram is excellent. I had a washing machine standpipe installation fail the inspection. I had created a forbidden S trap by not having a minimum of 6 inches of low pitch horizontal pipe just downstream of the U bend. S traps siphon because there is no lateral pipe for the water to flatten out in, therefore no air gap. Where a lateral enters a vertical pipe is the only place our inspector wants to see a sanitary T. For venting a T can be used anywhere. Pipe junctions in laterals are a Y+ 45 degree elbow combination with the Y positioned at 45 degrees from either side of plumb.

[Tom M King]

Here are the applicable codes, depending on which your locality requires:

https://forms.iapmo.org/email_marketing/codespotlight/2020/june4.htm

https://codes.iccsafe.org/content/IPC2018/chapter-8-indirect-special-waste

One of those codes does not allow a trap below the floor.

Minimum size was raised to 2" in 1967. I'm thinking the ABS installation in the rental house was before then because it was 1-1/2". That drain did not take the water and the washer drain hose was hanging over the side of the utility sink right next to it when we bought that house. The new PVC drain in the picture works like one is supposed to and takes all the water, no problem, from the largest size current model washing machine.

[Bill Dufour]

Are you saying you plan to pay to dump the water down the city drain?
Bill D

[Thomas McCurnin]

+1 Same here.

[Tom M King]

I know nothing about city sewer systems, but am curious to hear what you guys are asking about.

[Jack Frederick]

Where you get into trouble on most drains is when your vent arm is no correct/to far away/undersized. 2“ drain and a good vent lay-out and you are pretty good, but pay attention to Tom’s advise.