Clothes Washer Standpipe Drain Height Requirement

[fishe160]

Hi, long time listener, first time caller...

I am installing a clothes washer and am looking for some knowledge on the standpipe requirement in the installation manual. GE requests it to be 36'' from the floor, however I would like to make it closer to 32-33'' to fit into the enclosure it will live in. However, I would also like it to not spew water everywhere...

I haven't come across any posts that gave me enough confidence to shorten the pipe. This post talks about the air break, and the need to be above the wash drum/tub, but didn't really cover the height requirement: https://www.skoolie.net/forums/f50/w...eak-25795.html

I found some plumbing code verbiage, which matches what is in my house house, but it is only kind of helpful as there will be a Hepvo valve, not a trap: "No standpipe receptor for a clothes washer shall extend more than 30 inches (762 mm), or not less than 18 inches (457 mm) above its trap."

I called GE, but they said "Do what the requirements say". Fair I guess.

My current opinion: GE is adding height so that the air break is formed in the pipe. By ensuring the Hepvo valve is at least 18" + 5" for the air break below the top of the pipe, and that the top of the pipe is above the rim of the front loading drum (~10''), it will be ok.

Can any plumber skoolie type person add some clarity for me? I deeply appreciate your time.

[Iceni John]

I have a Splendide 2000 (model WD802) washer/dryer, and when I installed its drainpipe it ended up being slightly lower than Splendide's recommended height. The water drains out just fine, so I'm not sure why the pipe should have been a bit higher. My drain line, like all others in the bus, is 1" ID reinforced vinyl tubing connecting to a 1-1/4" waste water manifold between the frame rails that feeds into the top center of the grey tank, and everything works perfectly, without any Hepvo AAVs or air breaks anywhere! So far, so good.

John

[Albatross]

I would imagine that the requirements listed in the instructions are due to the natural resistances that are likely to occur when you're installing it in a house; namely that the drain pipe is going to be roughly the same size for quite a run, with some 90° turns that will add some flow resistance. They are expecting that pipe to run more or less parallel to the ground for a ways before dumping into a main sewer line or running out to some kind of septic system.



I would also imagine that the instructions did not remotely even consider the possibility that someone might try to install their product in an RV, much less a skoolie. The instructions even talk about "your water department can advise you on your water pressure", so it doesn't even seem to appear to them that someone might have a well-system where they are their own water department.



Considering that your drain pipe is certain to be much shorter than whatever is dumping into a sewer-main, probably by a few hundred feet, you are definitely going to have less flow-resistance, and considering that you're probably be going to dumping into a tank somewhere very close-by, it's almost certain that you could meet the requirements listed in the instructions.



The hint is in #1: eliminating 9.5 gallons per minute. This is likely the maximum flow-rate of the drain pump in that device, so you could very easily drag up three 5-gallon buckets of water and test the drain capacity of your pipe at the length you would like to have it, using something like a large funnel. Using a timer or stopwatch, see how long it takes you to either drain 10-gallons, or just keep dumping water so that there is a level of water in the funnel to make sure that, say, a 30"-32" standpipe could keep up with the demand.

[turf]

on your attachment, the picture of the back of the machine.... whats the corregated pipe across the top?

if its a drain, then your water level in the machine will be at least that high and your stand pipe level will need to match it and exceed it.

cheating their air break recommendation makes for the possibility of backflow. so what are you dumping into and are you ok with that getting sucked into your washing machine?

[Rucker]

Originally Posted by fishe160

Hi, long time listener, first time caller...

I am installing a clothes washer and am looking for some knowledge on the standpipe requirement in the installation manual. GE requests it to be 36'' from the floor, however I would like to make it closer to 32-33'' to fit into the enclosure it will live in. However, I would also like it to not spew water everywhere...

The issue is the volume of water that needs to flow quickly through the drain. Washing machines can have quite high volumes of discharge, and shorter standpipes may not handle the volume-especially if you add a Hepvo.

I haven't come across any posts that gave me enough confidence to shorten the pipe. This post talks about the air break, and the need to be above the wash drum/tub, but didn't really cover the height requirement: https://www.skoolie.net/forums/f50/w...eak-25795.html

I found some plumbing code verbiage, which matches what is in my house house, but it is only kind of helpful as there will be a Hepvo valve, not a trap: "No standpipe receptor for a clothes washer shall extend more than 30 inches (762 mm), or not less than 18 inches (457 mm) above its trap."

This requirement is probably associated with ensuring the bolus of water in the trap is not swept out (by too high a pipe) or the trap causing back pressure (and making water spew everywhere).

I called GE, but they said "Do what the requirements say". Fair I guess.

My current opinion: GE is adding height so that the air break is formed in the pipe. By ensuring the Hepvo valve is at least 18" + 5" for the air break below the top of the pipe, and that the top of the pipe is above the rim of the front loading drum (~10''), it will be ok.

Can any plumber skoolie type person add some clarity for me? I deeply appreciate your time.

Difficult call. Maybe mock it up and see how much water is dumped at a time?

I wouldn't recommend it but you could put that Hepvo horizontal, under the floor, and get the required freestanding height they recommend.

[Ross]

Most washing machine drain hoses have a U-shaped bend at the end that you just hang in the standpipe. The "air break" they're referring to is simply that the hose doesn't have an air tight seal with the "house" drain pipe. Hanging the drain hose in the drain with gaps around it provides the "air break". It's really a siphon break. Without it, the water will get siphoned out of the washer; and with some machines, the pump sometimes runs backwards in the cycle and without an air gap the machine will pump sewer water out of the drain into the washer tub. The "height of standpipe above the trap" concern is so the trap works right. An S trap or P trap (gravity trap) needs the proper standpipe length. Too high, and the water rushing through it will just suck the water right out of the trap and down the drain. Then you have no trap, and sewer gas comes up into the house. Too short of a standpipe, and you might not have a tall enough (heavy enough) column of water to push through the bend in the trap fast enough to avoid water backing up out the top.

I have a Splendide washer/dryer combo unit in a small cottage, not my bus. Its drain hose goes to a standpipe in the wall which is below the countertop, about 34 inches from the floor. No backups or problems. 2 inch pipe, but it's overkill. The volume and flow rate of water pumped out is not high at all. I don't know your GE model, but I would think if you gave it a 1 1/2 inch drainpipe straight down into a greywater tank with a hepvo trap you'd have no problems.

[fishe160]

Thank you all for the overwhelming response!
Through out this whole project its amazing to me how much building is based on doing things a standard way, and as soon as you deviate from that it gets gray fast. Everyone knows the How, but not always the Why.

TL;DR
I will make a mockup with the Hepvo and try dumping water and timing it (yay calculus!). We'll start with 1-1/2'' but if it needs more buffer time go to a bigger pipe diameter.

John- thanks for the real world results, invaluable. The manual for your washer wanted: "Needs a 1 ¼" (3.2 cm) minimum diameter standpipe with the minimum carry-away capacity of 7 gallons (26 liters) per minute. Top of standpipe must be at least 25" (62 cm) high and no higher than 34" (86 cm) from the bottom of the washer. " You're right in the sweet spot.

Albatross- thanks, thats a good summary of the why. It makes sense.

turf- yes the corrugated is the drain, but it is long enough to reach 50+'' high, so they put some extra in there. Its a front loading washer, so I don't believe that they could fill the machine with that much water, or the door would blow open I understand the backflow warning, makes sense.

Rucker- thanks, makes sense. Yeah definitely going to keep the Hepvo above the floor, too much stuff below.

Ross- thanks, I had thought of the too short overflow portion, but not of the too high sucks the trap empty concept. Also thanks for the real world knowledge.

[turf]

backflow is serious but if you understand how and why..... then you can manage it. they don't know where you are so the standard is what works everywhere. apparently they've seen crap jump a 4" gap, so their standard is 5".

a hepvo wont get sucked dry and stop working...... so, idk the standing head pressure of a hepvo but its not apples to apples with ptraps in this example.


try looking at Canadian washing machine drain standards, northern climates use more waterless traps than the us.

a quick search says "1 1/2" pipe 18" above the device".....

a hepvo is about a foot, so about 30" would be the lowest? but you need to keep your pipe as afar above the waterline as possible. with a horizontal hepvo you could go as low as 20". i'd stick with the manufactures recommended minimum of 36".
you may be able to modifiy the washing machine water level by lowering that corrugated hose...... flip the clamp down and lower it 3/4" maybe?
the line where the power cord crosses the the corrugated pipe is about your water level.

in an rv, is backflow possible? sure is.
a fullish waste tank is prime for backflow. how far does that waste pipe stick down into your waste tank? i know a washing machine company thats seen waste jump 4".

[fishe160]

Originally Posted by turf

backflow is serious but if you understand how and why..... then you can manage it. they don't know where you are so the standard is what works everywhere. apparently they've seen crap jump a 4" gap, so their standard is 5".

a hepvo wont get sucked dry and stop working...... so, idk the standing head pressure of a hepvo but its not apples to apples with ptraps in this example.


try looking at Canadian washing machine drain standards, northern climates use more waterless traps than the us.

a quick search says "1 1/2" pipe 18" above the device".....

a hepvo is about a foot, so about 30" would be the lowest? but you need to keep your pipe as afar above the waterline as possible. with a horizontal hepvo you could go as low as 20". i'd stick with the manufactures recommended minimum of 36".
you may be able to modifiy the washing machine water level by lowering that corrugated hose...... flip the clamp down and lower it 3/4" maybe?
the line where the power cord crosses the the corrugated pipe is about your water level.

in an rv, is backflow possible? sure is.
a fullish waste tank is prime for backflow. how far does that waste pipe stick down into your waste tank? i know a washing machine company thats seen waste jump 4".

This makes sense, thanks for doing the initial poke around about the Canadian requirements. Definitely don't want any backflow! I only want to shorten it from 36'' to ~32'', and while I don't mind following directions, it seemed crazy that 4'' would be the end of the world, especially after seeing other people use shorter pipes in other builds.

[turf]

the water level in the corregated pipe would be the minimum level for the drain to work. if you go lower, you may get a siphon going.

[nikitis]

Originally Posted by turf

the water level in the corregated pipe would be the minimum level for the drain to work. if you go lower, you may get a siphon going.

Consider that your bus may be tilted at certain parking spots so account for tilt in your height calculations.

[Albatross]

Another option might be to add a smallish riser underneath the washer, but I'm not sure how feasible that might be in your build. It wouldn't solve every problem, but it might solve the issue of keeping your drain pipe at 36". You might even be able to lift it closer to a foot and turn the riser into some storage. Of course, this solution would also raise some not-insignificant weight in the bus, which would increase the likelihood of wobbling side-to-side a bit more, but the ~200 lbs or less is mostly insignificant to the weight of the rest of the bus; perhaps I'm a bit more sensitive to that kind of thing being in a shorty.

[Ross]

Everyone is offering great info here. This forum is super consistent in that way, unlike much of the internet (YouTube, I'm talking to YOU).

I'm retired from 40 years of appliance repair. Will 32" work? Short answer, yes.
A washing machine pump generally is a high volume, low pressure pump. They can move a lot of water pretty fast, but can't lift it very high. A front loader has very little water in it, compared to a big tub top loader. The drain pump will put out its maximum flow right at first, when the water is pooled at the bottom during the pause before the "distribution spin". After the initial high flow, the pump will only deliver what's actually being spun out of the clothes, ie, not much in terms of volume. Basically a dribble.

The "distribution spin" is a spin speed that's higher than the washing speed tumble, but not nearly as fast as the extraction speed. The slightly faster speed serves to distribute the clothes evenly around the drum, to balance the load. The machine then tries to spin out the load, and MAY need to go through distribution again if it senses excessive imbalance. (speaking in very general terms here, I don't know your specific equipment)

With a front loader, the "high volume" we're talking about isn't really high, when compared to the huge gush you get out of a full top loader.

Standpipe requirements must accommodate old school top loaders flow rates. You're just not going to get flow like that from a front load machine.

A big advantage of the Hepvo valve is its ability to be installed in any position.

[Jolly Roger bus 223]

in a construction setting the distance from the air gap or washer box to the top of the p-trap or first turn has to be a minimum of 2 feet or the rush of the water backs up especially really soapy water.
but as ross mentioned.
and my experience is more commercial size top load washers.
i have learned commercial plumbing over 30 years by fixing other peoples (the real plumbers) mistakes after the building occupants move in and actually start put the stuff threw its paces.
i learned after have to open up a block chase wall to lower the cast iron p traps and piping for 5 or 6 washing machines. also it will be easier if you have the room for it to get a washer connection box with the hammer arrestors built onto the valves and they make some that also has the island vent (air admittance valve).

[Carrier6]

There isn't really a code since it's not a structure. The 18" min and 30" max you found is for suds relief because of pump discharge. If you get too much velocity the suds will fill the pipe and cause the water to back up out the standpipe. You will be fine anywhere in that range. The required air break is just a hose into the pipe, no sealed connection. And air gap is a vertical gap 2.5X the pipe size, but is not required on this installation.

[AlphaHare]

There is a code, NFPA 1192, that covers plumbing, propane, low voltage wiring, etc. Not a bad idea to refer to it for your safety, insurability, and resale. Here's a good diagram of the essential recommendations for washing machine drainage.

1192 wants 1 1/4" min dia everywhere, anything shared downstream must be the next size up. So 1 1/4" drains into 1 1/2", etc. This diagram references 1 1/2" pipe as being the mfg recommendation. If your machine recommends 1 1/4" then the downstream drain only needs to be 1 1/2".

The recommended height is likely just to exceed the theoretical washing machine maximum - if the drain pump failed, the water will get to the top of the drum before overflowing.

Washing machines typically use centrifugal pumps - they aren't very efficient but they don't clog easily. The maximum height probably represents something less than the maximum head the pump can generate.

IMO - don't overthink this. Your machine probably has a 3/4" drain line. 1 1/4" PVC has 3 times the area of that line - you are not going to have volume issues. Likewise, unless you use dish detergent by accident, clothes water isn't really sudsy.

If you end up a couple inches short on the standpipe you're probably going to be just fine.

[fishe160]

Thanks to everyone for their comments! I appreciate the time it takes to jot them down.

As a lazy person, I hate testing, but it really does put all concerns to rest. Here are my results:

Using 1-1/2'' SCH40 the standpipe height it will end up being is 34-1/4''. The height above the Hepvo is 22-1/2'', the Hepvo is about 7-1/4'', and the remainder is the elbow and slope whatnot.

During repeated tests, the max flowrate I could achieve was 9.23 gal/min (funnel was the limiting factor), and the pipe did not overflow. It was around 2-3'' below the top (hard to tell exactly). Note that it shares some volume with a sink drain and the Y (not finished).

Measuring the washing machine discharge, the highest flowrate was 4.51 gal/min during a small discharge after spinning. On average the flowrate was closer to 4 GPM. Typically 2 gallons were drained, and then a pause to spin, then another 2 gallons broken up over 2-3 more events. It was never sudsy.

So given the flowrate needed is half what the drain can handle, and the small volumes of water, I feel comfortable there will be a 4-1/2'' air gap maintained in the pipe.

I'll update the post in the future if there is a catastrophic failure once this bus is done and it is in use...