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Maximum Standpipe Height


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The UPC, Section 804.1 sez:

No trap for any clothes washer standpipe receptor shall be installed below the floor, but shall be roughed in not less than six inches and not more than eighteen inches above the floor.

Why do you suppose there's a maximum height of 18 inches?

Washing machine manufacturers all (nearly all?) allow their washers to be installed with standpipes up to 96 inches above the bottom of the washer. With a 30-inch standpipe, that would put the trap about 66 inches above the floor. If it's ok with the manufacturers, what problem is the UPC trying to address?

I'm thinking of basements where the sewer line might exit the basement at three or four feet above the floor.

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Trap at:

6" + 30" = 36"

Trap at:

18" + 18" = 36"

I get that, but why?

What would be the harm in putting the top of a standpipe at 96" if the washer manufacturer allows it and it allows one to avoid installing a sewage ejector?

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So the trap might be above the washer?

Then you have to worry about siphoning.

I think they're doing it 1. for convenience, 2. Possibly there is standard for length of discharge hose.

The whole point of the standpipe is to provide an indirect waste receptor, which makes siphoning unlikely.

It would be much less convenient to have to install a sewage ejector.

Supplementary hoses are easily available.

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Just thinking, shouldn't the top of the standpipe be below the top of the washing bowl, for overflow protection?

If so, then there's no mention of it in the codes or in the manufacturers' installation instructions.

How would that protect against overflow? Do you mean overflow at the standpipe or at the washer?

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Wasn't thinking straight about the siphoning?

How would that protect against overflow? Do you mean overflow at the standpipe or at the washer?

At the washer, if the discharge valve was stuck open and water continued to try fill the bowl.

For fun I went to the GE site and they only mention 30" minimum, no maximum stated.

http://products.geappliances.com/ApplPr ... TWN4250DWS

NOTE: If drain hose facility

does not meet 30" minimum

height requirement, thread

drain hose through supplied

anti-siphon clip U and mount

to cabinet back as shown

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Originally posted by patt

Wasn't thinking straight about the siphoning?

How would that protect against overflow? Do you mean overflow at the standpipe or at the washer?

At the washer, if the discharge valve was stuck open and water continued to try fill the bowl.

I don't think that any standpipe would guard against that, no matter what the height.

For fun I went to the GE site and they only mention 30" minimum, no maximum stated.

http://products.geappliances.com/ApplPr ... TWN4250DWS

NOTE: If drain hose facility

does not meet 30" minimum

height requirement, thread

drain hose through supplied

anti-siphon clip U and mount

to cabinet back as shown

Those are the abbreviated instructions for doofuses. Here's a full set of instructions, check out page 18, it say 96 inches, just like Maytag & Whirlpool:

https://www.ptsem.edu/uploadedFiles/Ope ... ctions.pdf

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So the trap might be above the washer?

Then you have to worry about siphoning.

I think they're doing it 1. for convenience, 2. Possibly there is standard for length of discharge hose.

The whole point of the standpipe is to provide an indirect waste receptor, which makes siphoning unlikely.

It would be much less convenient to have to install a sewage ejector.

Supplementary hoses are easily available.

Thanks , Jim. the first time I questioned the basement standpipe was where Mr Handy ran the drain pipe along a ceiling joist and then down to the main drain. The washer specs sheet said it could push a head of 96". His mistake was his standpipe was only 2" tall.

The air gap breaks the siphon. And it is actually harder to siphon with the hose raised, not easier. [:)]

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Suggested as a possible answer on another forum... could the maximum clothes washer trap height be based on the strong possibility that the installation would also include a sink, and the sink trap could be siphoned if the clothes washer discharge is above it? Stole the attached pic from the web, showing a typical install with a sink. Imagine the laundry trap well above the sink tee...

Click to Enlarge
tn_2015517214040_1425226_10204590337578177_3209284427605090948_o.jpg

24.74 KB

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Suggested as a possible answer on another forum... could the maximum clothes washer trap height be based on the strong possibility that the installation would also include a sink, and the sink trap could be siphoned if the clothes washer discharge is above it? Stole the attached pic from the web, showing a typical install with a sink. Imagine the laundry trap well above the sink tee...

Click to Enlarge
tn_2015517214040_1425226_10204590337578177_3209284427605090948_o.jpg

24.74 KB

That 2" vent stack provides plenty of air for the standpipe to drain, I think. There could be a sink on the floor below, not a problem with suction from the stack, I don't think. But I'm not plumber, so I'm open to correction.
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Suggested as a possible answer on another forum... could the maximum clothes washer trap height be based on the strong possibility that the installation would also include a sink, and the sink trap could be siphoned if the clothes washer discharge is above it? Stole the attached pic from the web, showing a typical install with a sink. Imagine the laundry trap well above the sink tee...

Click to Enlarge
tn_2015517214040_1425226_10204590337578177_3209284427605090948_o.jpg

24.74 KB

Seems like a real stretch. Wet venting is either not allowed or allowed with caveats by the various plumbing codes.

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Here's what the UPC handbook has to say on the topic:

"The clothes washer standpipe is considered an indirect waste receptor, not a fixture tailpiece, and, as such, has specific requirements for its use. The minimum and maximum elevations of the trap and the standpipe allow for flexibility in installation. It is not intended that this array of rough-in and standpipe elevations should result in a total rise above the floor of either 24 or 48 inches (the two possible extremes). The objective is to utilize a combination of these options that will have the clothes washer standpipe terminating at approximately 36 inches above the floor (kitchen countertop height) with a minimum of 24 inches of standpipe.

"The intent is to have the clothes washer riser at the flood-level height of the kitchen sink to prevent flooding at the clothes washer standpipe if a stoppage should occur downstream. It is also intended to be high enough to prevent gravity drainage from the clothes washer if roughed in below the water level of the washer. The 24-inch minimum is the height of standpipe required to eliminate the possibility of the clothes washer pumped waste from overflowing the standpipe."

Does anyone else find this explanation rather quaint?

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Here's what the UPC handbook has to say on the topic:

"The clothes washer standpipe is considered an indirect waste receptor, not a fixture tailpiece, and, as such, has specific requirements for its use. The minimum and maximum elevations of the trap and the standpipe allow for flexibility in installation. It is not intended that this array of rough-in and standpipe elevations should result in a total rise above the floor of either 24 or 48 inches (the two possible extremes). The objective is to utilize a combination of these options that will have the clothes washer standpipe terminating at approximately 36 inches above the floor (kitchen countertop height) with a minimum of 24 inches of standpipe.

"The intent is to have the clothes washer riser at the flood-level height of the kitchen sink to prevent flooding at the clothes washer standpipe if a stoppage should occur downstream. It is also intended to be high enough to prevent gravity drainage from the clothes washer if roughed in below the water level of the washer. The 24-inch minimum is the height of standpipe required to eliminate the possibility of the clothes washer pumped waste from overflowing the standpipe."

Does anyone else find this explanation rather quaint?

Thanks for the reference.

The first paragraph makes sense - so much so that it probably doesn't need to be said. The part about the kitchen sink is just silly. None of it explains why the top of a standpipe can't be installed at 96 inches.

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I guess I must now move my laundry room to the same level as my kitchen. Is there a program available to assist me with this traumatic time in my life.

Yes, In my case it would be a 16 step, one door and a hop skip and jump!

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