The waste hose through which the water is removed from my washing machine is inserted into a vertical pipe extending from the floor with a U shape at its end.

The problem is that there is foam coming out of the pipe where the waste hose is inserted.

Can I extend the pipe that is after (above) the U to leave more room for the foam to form and hopefully prevent it from overspilling?

Is there a height limit ?

If the hose can reach 1 meter above the washing machine, does it mean that it is safe to have the hose connected so high?

Is there a danger of causing damage to the washing machine's water pump that pushes the water outside if it has to push a water column that is too long/high ?

  • Are you referring to the trap? You should not force the hose through the trap.
    – Steven
    Dec 5, 2011 at 21:07
  • Totally mistook your comments about foam as relating to foam insulation / permanent shaped foam -- "forming foam" as in forming structure. Dec 5, 2011 at 21:09
  • anyway you can post a pic of your existing standpipe setup?
    – Zach
    Dec 9, 2011 at 16:20
  • Just wanted to update that After (encouraged by @Jeff Ferlands response) I add some 40cm or so of pipe and stretched the drain waste hose a bit (or to be more accurate - just placing its end inside the now higher entry point - as no real stretching was involved). It is now working great with no visible foam or water leaving the pipe. THat said, I will also try and reduce the amount of laundry detergent as suggested by metaEd. Thanks you all.
    – epeleg
    Dec 11, 2011 at 12:48

4 Answers 4


Experience tells me that at least some models of washer won't hold water unless the drain hose extends above the water level of the wash basin. I can't quite figure out what you're trying to say about extending pipes, but it should be safe to have the water drain out of the washer drain hose at its maximum height.

Eventually, the drain hose can be high enough that the water column overwhelms the pump (or hoses), but you'd have to be doing something bordering on insane to reach that. Every foot of height in a water column adds .43 psi of water pressure, so even a hose rising 15 feet above the washing machine will provide less than 7 psi of back pressure. I can't imagine a washing machine pump which doesn't handle that.

  • 1
    Damn, so I shouldn't discharge the dirty water out the roof?
    – Tester101
    Dec 5, 2011 at 20:48
  • @Tester101 No, you shouldn't, but more because of bacteria and environmental concerns. Also, you'd eventually get a very nasty looking roof. You could discharge to the roof with a booster pump and reservoir if you really wanted to, or even directly in a single story if the discharge distance doesn't overwhelm the pump or back-fill the washer too much. Dec 5, 2011 at 20:53
  • 1
    Pump it into the next door neighbor's hot tub. They will enjoy the suds and romanticize their experience.
    – lqlarry
    Dec 5, 2011 at 21:05
  • Thanks Jeff, your calculation of water column weight and estimate re influence on the pump was exactly what I was looking for. I only want to lift it by a feet or so, but was not sure if the was an issue with respect to the height of the washer itself.
    – epeleg
    Dec 8, 2011 at 10:47

An overflow of suds is what you get when you use too much laundry detergent, or when you use a cleaning compound that is not intended for use in a washing machine.

If you are using an appropriate product and you are getting excess foam (foaming out of the machine, or residual foam in the garments, or foaming out of the drain), cut the amount you use in half. If you continue to get foam, cut it in half again, and so on. For example, if you normally use 1 cup, reduce to ½ up, then to ¼ cup, and so on. Do this until you eliminate the foam problem.

If at that point you are not getting adequate cleaning, increase the amount by ½. For example, if you reduced the amount to ½ cup, try ¾ cup. If you cannot get adequate cleaning without foaming, your detergent is at fault. Get a better quality detergent and start over.

If you have a top loading machine, you can use any standard machine laundry detergent. If you have a front loading machine, you should limit yourself to detergents which are compatible with front loaders. These are often labeled "high efficiency" detergents. Foaming products, such as those made for manual washing of delicate garments, and other foaming products such as hand dish soap or soaps for hand cleaning, should never be used in a washing machine.

This answer is based on information I learned while managing a detergent manufacturing company and laboratory.

  • This is also related to the extremely comical occurrence of my mother once filling a dishwasher with regular dish soap. It approximated a en.wikipedia.org/wiki/Foam_party coming from the machine door. Dec 5, 2011 at 20:30
  • 1
    thanks, I will try that, but I don't think this is the real problem. Shouldn't any water with detergent foam when being pushed into "open space"? I think the foam is generated when the water from the hose hit the U. and since the pipe above the U is very short it just overflows instead of being washed away by the flow of the water. (I might be wrong though).
    – epeleg
    Dec 8, 2011 at 10:39
  • Ad agencies have convinced the public that detergents foam, but it's a misconception. It depends on the formulation. Vertical surface cleaners, for example, have a high foaming surfactant added. On the other hand, detergents which are used with agitation in a closed space, such as machine dishwash, machine laundry, carpet washers, and parts washers, use low foaming surfactants, and, if necessary, a defoaming agent such as silicone oil. Having said that, even plain water will froth up faster than the froth can dissipate, when injected at high pressure into an enclosed space.
    – MetaEd
    Dec 8, 2011 at 17:29

Can I extend the pipe that is after (above) the U (to leave more room for the forming foam (and hopefully prevent it from overspilling?)

You should not use any extender or splice the hose. This could be a place that could easily clog or maybe get pulled on and pull out of the clamps. Also, the water pump is only designed for the height shipped with the machine. Any length added to it could cause the pump to fail or not pump out all the water.

Is there a height limit?

In the US it is 42 inches. (Me being part of the evil-non metric society does not know how much that is in evil metric measurement.) 106.68cm Ask a local plumber or somebody in the plumbing section at your favorite diy.

If the hose can reach 1 meter above the washing machine, does it mean that it is safe to have the hose connected so high?

See my answer to Number 1

Is there a danger of causing damage to the washing machine's water pump that pushes the water outside if it has to push a water column that is too long/high ?

See my answer to Number 1

  • let me clarify as I belive I might have used the wrong term when I said "to extend": I do not want to add to the length of the hose. I just wanted to know if I can arrange it is such a way that its end is higher then the machine itself.
    – epeleg
    Dec 8, 2011 at 10:43
  • Just remember that if the hose is stretched too much the hose could pull out from the machine or wall if the machine is moved.
    – lqlarry
    Dec 8, 2011 at 20:03

Manufacturers of washing machines don't recommend exceedingly a 96" (8') lift from the height of the discharge hose. In other words a standard size washing machine will pump waste water to standard ceiling height if necessary in a basement to access existing ABS as opposed to having to access an iron stack for drainage just above the height of the washing machine. This also applies to HE machines.

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