Is there a limit to how far you can run horizontally with a 1-1/2 inch vent
before you go vertical or tie into a stack? Present vent by previous owne
r runs about 15 feet. I could tie it into a 4" stack only 4 feet away. Eve
rything is still open (basement) and accessible. Cutting a 4" vertical cas
t iron stack would not be fun, but maybe there are other methods of tying i
In a case like that, you should probably consider using an air
You see, the whole idea behind vent piping is to prevent the partial
vaccuum that can be created behind draining water from sucking the water
out of the drain's P-trap. By connecting an empty pipe (called a
"vent") to the drain pipe a short distance downstream of the trap, air
will be sucked into the drain pipe behind the draining water instead of
the water in the p-trap being sucked out.
An air admittance valve (also called a Studer valve after the company
that first marketed them) is really nothing more than a spring actuated
check valve. You mount it on the drain pipe a short distance downstream
of the P trap. If a partial vaccuum ever develops in the drain pipe
behind the draining water, the air admittance valve opens allowing air
to rush into the drain pipe behind the draining water, thereby ensuring
that there's no risk of the water in the p-trap getting sucked out.
You see, the worst that can happen if the water in your p-trap gets
sucked out is that you have the smelly air in the sewer coming up
through that empty trap to stink up your bathroom. That sewer gas isn't
pleasant, but it's not poisonous either. So, it's best to have your
drains vented, but where venting isn't practical, most jurisdictions
will allow you to use an air admittance valve instead.
Google "air admittance valve" or "Studer valve" and read all about them.
The air admittance device is probably the easiest option. The height of the
device is supposed to be above the fixture that it is venting.
Cutting the cast iron vent stack and inserting a tie-in there is an option,
but it can be tricky. For one thing, the pipe/stack above the cut needs to
be braced well so it doesn't drop down when you take out a section of the
I noticed that you recently posted:
"Sheet vinyl vs. tile??",
"Circuit Breaker as an input device",
and you received lots of replies to both questions. But, I didn't see any
reply back from you. Did you read what people wrote? Do you have ANY
follow-up on either of those questions and the responses that you received?
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.