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Does a basement sink require venting? Answered

 We live in a house built in 1979, and the builder subbed a drain pipe in the basement concrete for a wet bar.  They installed it far too close to the wall to build a bar, but too far from a wall to be useful in any way.  We have enclosed it in a small room behind a fish tank, and we want to make a small utility sink to drain the tank.  It doesn't have a water source, and it is awkwardly positioned in the room, even in this application.  I was looking through a home improvement book and saw a photograph of a basement subbed for a bath and it showed a sink vent.  Our drain most certainly doesn't have a vent.  Is this an issue?  Does every sink/drain need venting, or is it enough that (hopefully) the other drains in the house are vented?



8 years ago

So, there's a rough-in for a drain?  Do you know if the drain is connected to a toilet stack or something, that would act as a vent?  The connection might be buried in the foundation so it might not be obvious.

There was a bath roughed in to this basement as well, but on the other side of the room. I guess I could/should check to see if that sink is vented as well?!  That had been finished prior to our purchasing the house, but I guess I can't assume that the previous homeowner had it finished properly and vented!  Basically the drain pipe in this instance is a black pipe that stuck about a foot out of the poured concrete floor.  There are no pipes nearby or attached.  However, there is what looks like another pipe (steel?) that's flush with the concrete which has a sort of cap on it with a square knob on top.  It looks like it could be opened if you had the a big wrench or something.  Are we confused and the pipe sticking up should be the vent and the covered floor pipe is for the drain?  We added the p-trap and sink to the pipe that protruded.  I was told that it was a rough in for a future sink for a wet bar. Now I don't know exactly what we've got.  Maybe I should take a picture this afternoon to better explain.


Ha, now you've got me intrigued as well!  I think it might be best at this point to get a plumber in there to see it in person.  Even if you don't have them do any work, at least they'll be able to tell you what you've got!


8 years ago

Yes, it does.  The International Plumbing Code requires venting of all sinks, showers, tubs and plumbing fixtures where wastewater drains away.  For sinks, this is usually a 1 1/2" vent line either directly vented to the outside or tapped into a 3" or larger main vent.

...the international plumbing code AFAIK only applies to Americans and Canadians....

In the UK, we have no such requirement, except that means are provided to prevent vacuum in the pipes: this can be done with a valve.


I wish that part of a person's identity on Instructables was a little flag telling us where in the universe they reside.

Sorry, I updated the location.  Algonquin, IL, USA.


I'm sorry also, that was not meant as a direct jab at you.  But I forget when answering that not everyone lives and works under the same rules as I do, and I felt like tossing out a general whine.

The Location field is right there already. What we need is for the admins to make it mandatory, and provide a mechanism to limit it to real locations. People could still lie if they wanted to, but we'd be closer. Of course, I'd be sad about having to lose my "The Hellmouth, GA" location....

Well, I just keep forgetting the the world is bigger than my back yard.

Whether or not its required by law, it's still required in most cases for pragmatic reasons. Without pressure relief, there's a tendency for flow induced vacuum, which can (and often does) result in complete purge of the piping, which then opens your home to intrusion by sewer gases, since the water barrier has been removed..

Modern plumbing codes do require that all sinks etc. be vented.  But they now allow under cabinet vents.  Like in an Kitchen island sink.  I'm not sure of all of the details but it is doable and the plumbing works much better vented than non-vented.