If he suggests doing something that is not to code, then yes there is a cause for concern.

If that is the same thing as an island sink vent

it wouldn't be to code but if it's good enough for the island sink it's probably good enough for your sink.

Definitely a red flag but are you willing to pay to do it right?

Doing it right involves opening the walls and either vent through roof individually or tie into the vents of the highest bath group above the flood level rim.

I like that picture above in regards to island sinks but in my area....even though they are code.....have their vents seal off due to clogs on the flat run in the floor joist.

IOW, that second cleanout, which is a crucial one for proper operation...is never installed nor have a place to put it where it is accessible on the floor plan it serves.

Studor Vents aka Pro-Vents aka Cheater-Vent all fall within the same connotation that they are mechanical devices that can and WILL fail over time.

A plumbing system designed with vents as intended provides error free operation without the use of moving parts.

In other words, put it in and forget it. You don't afford that same luxury with cheater vents. I do agree however that "some" situations warrant their use...the degree of cost to vent correctly is immense sometimes on the older homes and can offer structural integrity issues.

I should clarify -- my contractor is very respected, licensed, etc, and I don't think he goes around doing things not to code. I think he suggested this b/c of the prohibitive cost of fixing this situation, and also because this is something that *is* within code in many counties in our state, and used to be to code in our county. So it's maybe a little different from doing something that is universally not to code. Does that make sense?

These pipes all run in an exterior wall. Is it possible to vent out the wall rather than running the pipe all the way to the roof?

Thanks again.

Amy

The Island Vent illustrated above is per the Uniform Plumbing Code.

The International Residential Code also permits an Island Vent but thier layout is a bit simpler.

Note that at the top of the island vent illustrated above both vertical risers have an 1/8 bend with a short section rising at a 45deg angle to a 1/4 bend forming a point on top. In plumbing any line rising at a 45deg or greater angle is said to be a vertical pipe so technically all the pipe in the UPC configuration is vertical pipes. This is because the code does not permit any horizontal dry vents until the vent reaches an elevation of 6" above the flood level rim of the highest fixture served by that vent.

The IRC permits using a 1/4 bend on the top of both vertical risers and a flat horizontal section connecting the risers.

Also note that the UPC requires a vent be attached to the opposite riser from the fixture arm. The IRC island loop does not require any additional venting.

Under the UPC all vents must terminate through the roof. The UPC will permit a maximum of one AAV (air admittance valve- common name -studor vent) per structure with the expressed written approval of the local inspecting authority.

The IRC requires all structures to have one "Main Vent" which must run undiminished in size from the house main drain through the roof. After the main vent is achieved auxilliary vents may terminate through the roof, in the attic space, through a sidewall under certain conditions or you may use an unlimited number of AAV's.

I think the contractor may have been proposing an AAV (AKA Studor) not an island vent.
AAVs have their own set of problems since they have moving parts in the form of teh diaphragm that seals off under pressure but allows air in under vacuum.
They also must be installed in an accessable location and not concealed within finished walls (covered with a removable panel is OK).
AAV acceptability varies all over the place, they are often not allowed in places that have local codes and are not very interested in updating them.
After all it worked fine for Grandpa.