Washing Machine Standpipes Questions

[MarkSLSmith]

Folks,

In my new (to me) house, we recently overflowed the 2 inch standpipe.  Fortunately, we were standing right next to it, so the impact was probably minimal (although there is a wood floor on the other side of the wall!).  Having previously existed in a state of blissful ignorance about the whole subject of washing machine drainage, I have been trying to learn everything I never wanted to know.  It would be great to get some help from the WN community, especially question #3.

1.  I think my standpipe has a P trap, similar to the one shown in the picture.  From underneath the floor in the crawlspace, I couldn't see a P-trap.  However, when I stuck my endoscope down the standpipe, I observed water at the bottom of the standpipe.  Also, I attacked the standpipe with a plumbing snake, but I hit a brick wall and couldn't go any further; I assume this is the bottom of the P-trap and the snake was unable to navigate through the trap.

1a.  Is this a common plumbing arrangement for the standpipe?
1b.  Is the P-trap always above the floor and behind the wall?  
1c.  If the answer to 1b is yes, how does one access it for cleaning?  Is it assumed that it never needs cleaning because it generally only has water running through it?

2.  I think the root cause of the problem is my washing machine.  Holy guacamole, that washing machine pumps out the water at an amazing flow rate.  We routed the drain hose to a nearby utility sink (decently sized), and a large washing load filled up the sink 2/3 full before the water had much of a chance to drain out.  So my theory is that the washing machine drain may be flowing at a rate which is either dangerously close or even sometimes exceeding the capacity of the standpipe to drain it.  One might think that the standpipe is undersized, however the washing machine manual specifies either a 1.5 or 2 inch standpipe.  At least I have the 2 inch standpipe.

3.  I have considered 3 solutions.  One, do nothing and pray to the plumbing gods for deliverance from my affliction.  Two, the big box store sells a "standpipe adapter" which looks a like a large rubber stopper through which you insert the washing machine hose.  I guess the idea is to try to plug the top of the standpipe so that the water can only drain downstream.  Three, I could buy an extension to the drain hose and permanently route the hose to the aforementioned nearby utility sink.  The volume of the sink would provide a buffer against overflowing.  The longer hose run would be a bit unsightly, but probably better this than causing a flood.  I welcome comments/votes on any of these solutions, or any other solution that one might care to offer.  

Further information: the house was not designed with any sort of secondary drain system.  

Considering the close proximity of some very nice wooden floors, I really want as close to a 100% reliable solution as I can get.

Thanks,
Mark

[Woodenfish]

I’m not a plumber but I know that water won’t go down a pipe without air coming back up. Looking at your drawing you might want to look at the vent going up and see if you can rod it going down. Capping the pipe will most likely end in quite a surprise.

[KC]

Folks,

In my new (to me) house, we recently overflowed the 2 inch standpipe.  Fortunately, we were standing right next to it, so the impact was probably minimal (although there is a wood floor on the other side of the wall!).  Having previously existed in a state of blissful ignorance about the whole subject of washing machine drainage, I have been trying to learn everything I never wanted to know.  It would be great to get some help from the WN community, especially question #3.

1.  I think my standpipe has a P trap, similar to the one shown in the picture.  From underneath the floor in the crawlspace, I couldn't see a P-trap.  However, when I stuck my endoscope down the standpipe, I observed water at the bottom of the standpipe.  Also, I attacked the standpipe with a plumbing snake, but I hit a brick wall and couldn't go any further; I assume this is the bottom of the P-trap and the snake was unable to navigate through the trap.

1a.  Is this a common plumbing arrangement for the standpipe?
1b.  Is the P-trap always above the floor and behind the wall?  
1c.  If the answer to 1b is yes, how does one access it for cleaning?  Is it assumed that it never needs cleaning because it generally only has water running through it?

2.  I think the root cause of the problem is my washing machine.  Holy guacamole, that washing machine pumps out the water at an amazing flow rate.  We routed the drain hose to a nearby utility sink (decently sized), and a large washing load filled up the sink 2/3 full before the water had much of a chance to drain out.  So my theory is that the washing machine drain may be flowing at a rate which is either dangerously close or even sometimes exceeding the capacity of the standpipe to drain it.  One might think that the standpipe is undersized, however the washing machine manual specifies either a 1.5 or 2 inch standpipe.  At least I have the 2 inch standpipe.

3.  I have considered 3 solutions.  One, do nothing and pray to the plumbing gods for deliverance from my affliction.  Two, the big box store sells a "standpipe adapter" which looks a like a large rubber stopper through which you insert the washing machine hose.  I guess the idea is to try to plug the top of the standpipe so that the water can only drain downstream.  Three, I could buy an extension to the drain hose and permanently route the hose to the aforementioned nearby utility sink.  The volume of the sink would provide a buffer against overflowing.  The longer hose run would be a bit unsightly, but probably better this than causing a flood.  I welcome comments/votes on any of these solutions, or any other solution that one might care to offer.  

Further information: the house was not designed with any sort of secondary drain system.  

Considering the close proximity of some very nice wooden floors, I really want as close to a 100% reliable solution as I can get.

Thanks,
Mark

Mine (done by plumbers three years ago) is exactly like the picture.

[harderhandyman]

Had a tenant once that got a higher capacity washer that would overflow the standpipe.  We stuck a fitting in the end of the hose that limited how much water could come out at a time and that seemed to help.

[sweensdv2]

Your issue might be caused by a lint buildup in the p-trap or discharge piping. If you are not already using one, a mesh lint trap may help, https://www.menards.com/main/plumbing/pl...c-9414.htm .

[Cabinet Monkey]

2” pipe is standard and should be fine unless you have some sort of commercial washer like you’d find at a hotel or linen service.  Even then ,………..

What brand /model are we dealing with ?


I’d prefer the p-trap closer to the floor - at least below the tub of the washer. Doesn’t look to be the case from your drawing.  It’s always (supposed to be) above the floor.  Usually concealed in the wall.  Even if it wasn’t , it’s a glued trap and not serviceable.  

I’d suspect blockage in your pipe(s) or inadequate venting design.  That could be blocked too. Seems likely since you sink is slow draining too.

[MarkSLSmith]

2” pipe is standard and should be fine unless you have some sort of commercial washer like you’d find at a hotel or linen service.  Even then ,………..

What brand /model are we dealing with ?


I’d prefer the p-trap closer to the floor - at least below the tub of the washer. Doesn’t look to be the case from your drawing.  It’s always (supposed to be) above the floor.  Usually concealed in the wall.  Even if it wasn’t , it’s a glued trap and not serviceable.  

I’d suspect blockage in your pipe(s) or inadequate venting design.  That could be blocked too. Seems likely since you sink is slow draining too.

For clarification, I don't know what's behind my wall because I haven't opened it up.  I assume the drawing (pilfered from the internet) is a reasonable representation.  As stated above, my testing has indicated that there is a P trap.

The washer details are shown in the picture.

Thanks,
Mark

[Cabinet Monkey]

For clarification, I don't know what's behind my wall because I haven't opened it up.  I assume the drawing (pilfered from the internet) is a reasonable representation.  As stated above, my testing has indicated that there is a P trap.

The washer details are shown in the picture.

Thanks,
Mark

That's a reg. ol  SpeedQueen.  Good machine BTW, nothing special or out of the ordinary though.  2'' pipe will handle that no prob. It's the exact setup in a house I bought 2 yrs. ago, so I know it works.

I'd investigate a line blockage or blocked/ insufficient vent stack first.

[Snipe Hunter]

If a plumber installed the pipe, there is a P-Trap. If there wasn't a P-Trap, you'd probably smell sewage. My guess is you have lint clogging the P-Trap.
You should be using a lint trap on the discharge hose. 2" pipe is the correct pipe. Don't close off the top of the standpipe. It will not drain as it needs air admittance from the top of the pipe for water to flow. You may also have a plugged vent stack slowing the water velocity but I doubt it. 9 times out of 10, it's a clogged P-Trap... especially if you aren't using a lint trap.

[Woodenfish]

Another thing you might try is a medium-sized rubber drain bladder available Home Depot. Harbor Freight, etc., and blast that clog out of the P-trap. Be sure to turn the water off and let the water drain out of the bladder for a while before removing it.