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 Double Trapping
Author: HelpMePlumb (FL)

I know the plumbing code forbids double traps, but why is it such a no-no?

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 Re: Double Trapping
Author: dlh (TX)

for one it slows down the drainage for two it makes it difficult to clean the line

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PLUMBERS "Protecting The Health Of The Nation"

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 Re: Double Trapping
Author: LemonPlumber (FL)

If at any point the tubular between is full.it must evacuate both traps be for release of vacuum can occur. Negative pressure is pure.

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 Re: Double Trapping
Author: hj (AZ)

They hyrdraulic principles working on the air between the two traps will either prevent drainage entirely, or slow it down initially. IF you can get the fixture to start draining normally, (and that depends on other hydraulic principles occurring), then it will continue until the sink is empty.

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 Re: Double Trapping
Author: packy (MA)

it would be hard to continue AFTER the sink is empty..

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 Re: Double Trapping
Author: woberkrom (MO)

I can think of a situation where water legally passes through three traps...

--Will

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 Re: Double Trapping
Author: woberkrom (MO)

TRIPLE TRAPPED!

A trap under a laundry sink (one trap) with a long indirect drain into a floor drain (two traps) that runs into a drain that exits the house and passes through a yard trap (three traps) before connecting to the public sewer.


--Will

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 Re: Double Trapping
Author: LemonPlumber (FL)

Any indirect p-trap is only installed as oder issues.How about a whole house with only one p-trap?and it is the toilets.I call it, the sweet taste of indirect waste.

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 Re: Double Trapping
Author: hj (AZ)

It can "legally" pass through a dozen, IF each trap has a vent. IF there are no vents, it makes no difference if they are "legal" or not the water will not drain.

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 Re: Double Trapping
Author: hj (AZ)

A sink with an indirect connection to a floor drain DOES not need a trap, and if it does not have a vent, then it will siphon, although the floor drain trap will negate any deleterious effects of the loss of seal. The floor drain may, or may not, have a vent, but the entire system should have at least one vent which would negate the double trap effect of the house trap. You are intentionally misapplying the prohibition regarding double traps.

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 Re: Double Trapping
Author: hj (AZ)

IF you read the statement properly, I am saying that if, or when, the double trap effect is overcome, the vessel drains properly until it is empty. At THAT point the next usage repeats the process, it does not get any "carry over" from the last time it drained.

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 Re: Double Trapping
Author: woberkrom (MO)

Indirect drains over a certain length need a trap (I want to say ten or fifteen feet), and then they need a vent if they are past yet another point.

I just thought it was a neat thing. For every rule, an exception. You are absolutely correct about a "true" double trap possibly not draining.

I was just having some fun "intentionally" constructing a counter example.

Fun. Fun. Fun.

I like to have fun.

--Will

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 Re: Double Trapping
Author: dlh (TX)

over 5' it needs a trap over 15' the trap will need a vent and the vent can not tie into a vent connected to the sewer

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PLUMBERS "Protecting The Health Of The Nation"

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 Re: Double Trapping
Author: hj (AZ)

In any case the trap only obstructs odors originating in the sink's drain line. ANY branch without a trap, regardless of its length, will be an "S" trap and therefore WILL siphon every time the sink drains. It is a "useless" reguirement, since the vent is often just a tee with a short uncapped riser, and the locations of the sinks are seldom where you could install an independent vent through the roof.

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 Re: Double Trapping
Author: PBwrencher (WI)

Double trapping creates an air-lock between the two traps thus impeding flow and not permitting proper air flow in the drainage system that promotes bacterial growth that helps keep the piping cleaner then it would be with no air flow.smiling smiley

There are special requirements in all plumbing code that require certain fixtures and applications tobe double trapped in various ways however; if your not deeply involved in the plumbing industry there is no need to even get into it.smiling smileythinking



Edited 2 times.

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 Re: Double Trapping
Author: hj (AZ)

quote; There are special requirements in all plumbing code that require certain fixtures and applications tobe double trapped in various ways however

I have NEVER heard of any fixture that requires a double trap, and since double traps are universally prohibited, I cannot imagine any fixture requiring it.

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 Re: Double Trapping
Author: PBwrencher (WI)

Scullery sinks to grease traps, indirect waste piping serving bar sinks, ice chest, ice cream dipper wells to open-site drains, Laboratory sinks acid waste to acid waste traps, mobile home parks with house traps serving the homes fixtures.smiling smileythinking

Iam sure you know these..maybe you just forgot.smiling smiley

If you want to more or you need your memory refreshed, I would have to charge you.smiling smiley

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Edited 1 times.

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 Re: Double Trapping
Author: hj (AZ)

NONE of those are "double traps", they TWO traps and they have vents between the two which a "double trap" does NOT.

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 Re: Double Trapping
Author: dlh (TX)

those have 2 traps with a vent or a gap between them thus they are not "double trapped"

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PLUMBERS "Protecting The Health Of The Nation"

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 Re: Double Trapping
Author: LemonPlumber (FL)

Packy.If the sink only was the problem then it would not be a problem, The traps they should protect, not as posted opposed and then, surely defect.

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 Re: Double Trapping
Author: PBwrencher (WI)

Two traps on the same drain line serving a fixture is a double trap, 2 traps = double.thinking smiling smiley



Edited 1 times.

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 Re: Double Trapping
Author: dlh (TX)

but if they are separated then it is 2 different drains thus not "double" trapped

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PLUMBERS "Protecting The Health Of The Nation"

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