venting distances

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ES Frame

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I'm 4 ft 10 inches from stack to trap arm on a bathroom sink using a 2 inch pipe. Is this ok ? my area is covered by the UPC
 

John Gayewski

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I'm 4 ft 10 inches from stack to trap arm on a bathroom sink using a 2 inch pipe. Is this ok ? my area is covered by the UPC
Your trap arm is the piping section from the trap to the vent. Are you saying your trap arm is 4 feet 10 inches?
 

Jeff H Young

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There's more to it than simply distance from the stack... What's above this in the stack?
Breplum nailed it question answered perfect. ESframe asked and provided all the info he chose We would all be happy to elaborate if he still needs help , as there are situations where you cant just cut any ol pipe and wet vent a lav
 

Tuttles Revenge

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There's more to it than simply distance from the stack... What's above this in the stack?
And even what is below the point of connection on the stack..

What is the stack used for. Drainage from above or venting from below? A vent stack you don't want to drain down, because the fittings and slope might not be correct for drainage. And you don't want to use your drain stack for a vent..

A trap arm that is being upsized is technically supposed to have the trap the same size too. A slightly longer trap arm runs into the problem where the overall length and slope causes the bottom of the pipe at the trap to be over the opening of the vent. IE: the run with slope is over a whole diameter of the pipe.
 

Jeff H Young

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Of cource if UPC code officials agreed with the above we would run 6 ft trap arms on 1 1/2 and have no siphon effect. but we have a higher standard I dont know why in case the trap arm isnt perfectly graded or it gets partially reduced in size by soap scum buildup possibly . they are only minimum standards We have codes to follow every detail dosent have a given reason. Also would a 1 1/2" lav into a 4 inch vent stack disturb fixtures below My guess is maybe but likely no (a bad way to plumb though), nevertheless standards for a quality build are important to serve a rough plumbing system to last many years /decades.
 

Tuttles Revenge

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We have codes to follow every detail dosent have a given reason
There are reasons... but they're not explained in the code book. The illustrated code book goes into further depth of why certain codes are the way they are.. and if you really want to get into the weeds, you can read some of these discussions on the Iapmo page.. but its really dry reading.. no real drama. at least publicly.

And honestly I believe some of the things in our codes are there because of tradition and no other good engineered reason.
 

John Gayewski

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If a pipe runs half to two thirds full, then you run 6ft on a 1.5 inch pipe, you have cut the air space above the waterline off from the atmospheric vent opening. That's why the trap arm distances are shorter in the upc. It's generally just more stringent engineering in the upc. In real life the trap might only siphon under very particular conditions. Such as you fill a sink and pull the plug. But most times having your vent within 6' of a 1. 5 trap won't siphon the trap. Most times it won't siphon even further. Where the line is drawn is just up to a vote from IAPMO which is made up of plumbers and engineers. People make presentations and have arguments at IAPMO meetings discussing things like pvc vtr pennatrations and how they need to be painted due to sun exposure, then someone says well what about the inside of the pipe it will still be exposed to the sun, then someone says it should be painted inside and out. Then someone says well won't that make the pipe smaller? I'm sure it's a great time, lol.

I believe IAPMO set out to make a code that could be follwed in any circumstance and be bullet proof in its design while being influenced by solely American design standards. If you look at some of the allowable designs in the ipc the engineering is very permissive and likley wouldn't stand up to every condition. Let alone that if a group of American engineers and plumbers wanted something to change in the ipc I doubt they would have very much influence.
 
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