Re: loop vent
Posted by hj on December 25, 19100 at 09:31:25:
In response to Re: loop vent
Some jurisdictions allow you to use a 3" branch to the island/loop vent location. Then you install the 2" loop vent off the top of the 3". The upper portion of the 3" then becomes the venting area. This is the same as a commercial waste and vent system for multiple floor drains where there is no way to individually vent them.
And some of the least sophisticated loop vent installers do not install the separate vent when the drain line is discharging vertically down to a lower level, assuming that by the time the vent becomes functional there will adequate air volume in the waste stack to break the siphon in the trap. This version does not function as well if connected to a horizontal drain line. The fourth option is to install an air admittance valve at the top of the waste pipe. All four operate equally well when everything is flowing properly and none of them function when a partial stoppage of the waste system occurs. Another consideration is that each jurisdiction has the option of approving these versions and often only accept one or two of them. They will normally have a diagram of their preference.

: In a response to a previous question, I became aware that there are 3 ways to install a loop vent. I know of only one way: from the standard sanitary tee in the wall a vent pipe connects into the top and goes up as high as it can and then loops around with a 45, 90, and 45 bringing it down through the floor where another sanitary tee (or combo wye) connects in to allow for a vent pipe to join the side inlet of that tee and from the bottom of that tee a pipe continues down and over to join up with the drain which extends down from the bottom of the first sanitary tee.What are the other 2 possibilities?

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