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What is the reason behind maximum length =4" for a p trap seal ?

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  • Mar 24th, 2021 6:26 am
[OP]
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Jun 27, 2015
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East York, ON

What is the reason behind maximum length =4" for a p trap seal ?

Based on multiple Google search results the maximum seems to be 4"
https://www.google.com/search?q=plumbin ... l%22+lengh
What is the law of physics that imposes this constraint ? What happens if you make it longer ?
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Oct 15, 2007
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CuriousC wrote: Based on multiple Google search results the maximum seems to be 4"
https://www.google.com/search?q=plumbin ... l%22+lengh
What is the law of physics that imposes this constraint ? What happens if you make it longer ?
Canadian code , there is no maximum ,
but the theory behind it is if the trap is too deep, the water may flow through too fast which can lead to siphoning of the trap seal and debris buildup
/thread
Everything has been said before, but since nobody listens we have to keep going back and beginning all over again. - Andre Gide
[OP]
Deal Addict
Jun 27, 2015
2070 posts
355 upvotes
East York, ON
Thank you
Does this look ok to you
Image
Lots of crazy 💡
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Oct 15, 2007
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CuriousC wrote: Thank you
Does this look ok to you
Image
Looks fine. Your trap seal is 2.5” there. You’re not measuring it properly
Everything has been said before, but since nobody listens we have to keep going back and beginning all over again. - Andre Gide
[OP]
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Jun 27, 2015
2070 posts
355 upvotes
East York, ON
Thank you I am trying to make room for the coupler that makes the transition from 2" to 1.5"
Interesting that the tub was OK with 1.5 but the shower needs 2"
the drain was OK with the tub and the shower so I kept is as it was (1.5") hence the need to make the transition
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Oct 15, 2007
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CuriousC wrote: Thank you I am trying to make room for the coupler that makes the transition from 2" to 1.5"
Interesting that the tub was OK with 1.5 but the shower needs 2"
the drain was OK with the tub and the shower so I kept is as it was (1.5") hence the need to make the transition
It’s because a shower has a lower threshold, and also code requires a 2” drain for any shower with more than 1 head/outlet
Everything has been said before, but since nobody listens we have to keep going back and beginning all over again. - Andre Gide

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