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Question DetailsAsked on 11/30/2017

can I hook up my washer discharge hose up to pvc and go up another 3 feet and over 3 feet to the 4 inch sewer pipe,

this would be right before the sewer pipe exits the basement. i believe there would neeed to be a check valve in here after the trap that would exist between the washer discharge hose and the pvc.

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Oh no - no way. Several major problems with that:

1) First and foremost, you need an airgap between the discharge hose and the sewer to prevent backflow to the washer - and a checkvalve is NOT the way to prevent that, especially with a clothes washer, because backflow check valves clog up with lint so end up staying at least partway open all the time - not to mention being a big-time code violation.

2) going up 3 feet additional your washer might or might not be able to handle, depending on brand - usually rated to only about 39-48 inches from floor to the gooseneck discharge point, though raising the washer on a pedestal can increase that height. But doing so means if the existing backflow checkvalve on the washer drain line (right after the pump in the washer, IF yours has one - most do NOT) leaks as they usually do, instead of having about 3 feet of water from the discharge line (much of which drains out by syphoning at the end of the cycle, so little runs back into the washer) you would have 6 feet worth which is more than will normally syphon out - so you would normally (at least after any washer backflow preventer valve cruds up some) get about 3 feet of discharge pipe backflow into the washer, sitting in it and going stagnant and stinky between uses - possibly enough to even sit in the bottom of the tub and cause it to go slimy and eventually rusty.

3) As I read it, you are talking going up 3 feet more (so presumably 7-8 feet off the floor into the main floor subfloor to reach the DWV stack line), then sideways 3 feet horizontal into the sewer line. This would mean your washer drain line would all be on a level with or below the sewer line level. You suggested a backflow preventer valve there - risky but maybe workable if they actually worked, but as stated in 1) above they are pretty much guaranteed to leak after a month or so, so your washer drain line would become a drain for the sewer line - flowing down it into your washer till it overflowed. Also - you would at least have had to go another foot or so up to get a trap in, even if your scheme worked - so 8-9 feet above basement floor.


Now - right way to do this, depending on your situation - which a Plumbing contractor (your Search the List category for this) can work out for you, is one of six ways I can think of, depending largely on the lift capacity of your washer and outside ground/sewer elevations:

1) get the washer out of the basement (presuming there is no sewer line down there already which it can tie into - from a basement bathrom, floor drain (and no, NOT sump pump), etc.

2) run the discharge hose up to a point legal height ABOVE the sewer line (commonly minimum 18-30" (30" in most areas) standpipe ABOVE the trap which would then be connected to the sewer line) in the walls (so up into an upstairs wall), then discharging as normal into an airgapped vertical pipe down to the trap then to the sewer line. In most areas the code requires that the trap also has to be 6-18 inches above the sewer/DWV line, to prevent the trap getting filled up with sewage from the sewer line), making a total 24-48" height required from where the discharge line goes into the air gap at the DWV line to the DWV stack/sewer line elevation. This would put your washer discharge point probably (assuming 7-8 foot basement ceiling height) some 9-12 feet above the basement floor. I don't know of any washer which can lift that high - plus the backflow from the discharge hose from air gap to washer after it quits pumping out would still create the same stinky/ slimy washer problem.

Couple of articles/graphics here on legal setup for gravity flow:

3) Discharge (as discussed in second article) into a washtub which drains to a lift pump capable of handling heavy lint load (another issue in itself - not a cheap pump and a maintenance issue) or directly to a stack pipe with trap (per first diagram) then into a lift pump. The lift pump would then lift it to above the upstairs sewer stack line to an airgap then dumping into the DWV stack/sewer line at first floor level.

4) Variation on above - rarely done, and makes the washer hose airgap the first place a sewer line backup will come out - is - IF the sewer line is deep enough in the ground outside, to run the washer discharge to a stack per first diagram above, then a separate DWV drain line to the sewer line outside - making a second through-foundation connection to the sewer line. This would require that the sewer line outside be below or (depending on code requirements for standpipe and trap height above sewer line) at least not much above basement floor level, so probably only feasible in areas with quite deep sewer line burial - so areas with deep frost penetration. Not legal in many areas, as many codes require only one DWV exit from the house, and would have to intercept the sewer line upstream of the outside cleanout.

5) Rarely legal except in rural areas, is to run washer discharge water directly to the ground - of course at legal distance from discharged water flow to any well or stream (typically 50 feet), and typically is led to a surface ditch leading to trees or such which need watering - though I have seen it led to a small leach field or wetwell to dissipate the water. Also has to discharge to the downhill dside of the house so the water does not work its way back to the foundation. Needs a free-airspace (not stuck down-in) airbreak at the discharge point, so the washer would have to be rated to lift the water high enough get it at least a foot or so above ground level to discharge to a drain line leading away. Of course, unless really getting complex with the drain line, works only in areas without freezing conditions at any time during the year.

6) Go with discharge per code requirements, to main floor drain lines as you wanted, using a high-lift washer - there are ones rated for up to 8 feet of discharge lift, though that does not solve the backflow into washer problem when it shuts off and the built-in backflow checkvalve cruds up. I don't know if high-lift retrofit pumps are available for existing washers - maybe, but probably $250-300 so a good portion of the cost of a new washer if there are. If your basement has a lot of free unused space, I have seen people raise the washer several steps up on a wood platform (restrain it so it can't walk off the platform in a spin imbalance situation) - make steps large (from front to back and from side to side) for easy negotiating while carrying laundry if you do that, and of course only so far you can do that without getting into headroom problems.

So - now that I have burst your bubble - good luck with choosing a solution. If the washer is the only water-consuming device/fixture in the basement I would NOT recommend going with a lift pump solution - expensive and high-maintenance solution for only that one demand - I recommend finding an upstairs location if possible (presumably there is already one there if you are encountering this situation).

If you want clarification of anything I have said before you talk to a local plumber, you can reply back using the Answer This Question yellow button right below your question. Local plumbing inspector for your city/county building department can answer questions (they commonly have an online guide sheet) about required discharge pipe stickup above trap and trap above DWV branch/stack height and such. Probably would have to call about surface discharge of the waste water - which of course can only be "gray water" from washer, not combined with sewage.

Answered 11 months ago by LCD

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