Sink venting

[inspectorwill]

So there are two sinks that sit right in the middle of a large 2nd floor master bathroom suite. I run the sinks and get a strong sewer gas smell before looking around and realizing there does not seem to be a feasible way for the sinks to be vented as far as I know (key point). The sinks are situated on and island cabinet with what I call a partition wall behind them that does not extend to the ceiling. The shower, tub and toilet are at least 8' away and there is no other wall within 6'. Additionally, I did not see any island type venting nor air admittance valves in the cabinets under the sinks. The partition wall is about 6" thick and I cant imagine an island vent was installed within the cavity. The home has been remodeled a few times over the past 20 years and I suspect they cut off the top of the wall behind the sinks that originally extended to the ceiling to open up the master bathroom. The house is 3 stories and I could not get to the roof to look for an abandoned vent and there is no attic space because the ceiling is vaulted. A roofing contractor checked the roof the day prior to my inspection so I couldn't coordinate with him. I am calling it out as a venting issue unless someone has any other ideas on how the venting could be accomplished. However, it still smelled horrible so I am going to call that out. I included a couple pics from different angles to show the bathroom configuration. Thanks as always.

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[Marc]

Are the fixtures trapped?

Marc

[inspectorwill]

Yes

[Erby]

Do you have a picture of the piping under the sink?

[inspectorwill]

Thought I had photographed it but unfortunately not.

[kurt]

Chicago Loop

Or, it's not vented at all.

[inspectorwill]

Kurt, I don't see much difference with the Chicago Loop versus a typical island vent which would have to be in the wall cavity since it was not visible under the cabinet. There were also no clean outs on the walls beneath the cabinets which I would expect to see with this venting. Would the lack of a vent cause the sewer gas smell since the gases are not displaced through a vent? I know that it is not a sure indicator but the combination of smell and visible configuration seemed to make sense for my initial suspicion.

[Scottpat]

The lack of the vent would not cause the sewer gas smell, the lack of a vent would impede the draining of the sinks. Did you see a drain in the floor, was one one of the sink traps dry when you started, shower or tub drain dry? Did it have a mechanical or AAV vent on the line under the sink?

Outside of that I would take a SWAG that they cut the vent pipe off in the wall and left it open or it has a mechanical vent on it and it has failed.

[Marc]

The lack of the vent would not cause the sewer gas smell, the lack of a vent would impede the draining of the sinks. Did you see a drain in the floor, was one one of the sink traps dry when you started, shower or tub drain dry? Did it have a mechanical or AAV vent on the line under the sink?

Outside of that I would take a SWAG that they cut the vent pipe off in the wall and left it open or it has a mechanical vent on it and it has failed.

Wouldn't the lack of a vent result in drain action pulling the water from the trap?

Marc

[kurt]

It can, certainly, but it's not likely. Water sticks to the outer walls of pipe as it drains; air can move in the middle. I'm not saying vents aren't necessary, but drains don't siphon in the hysterically extreme manner described by most plumbers.

[Scottpat]

The lack of the vent would not cause the sewer gas smell, the lack of a vent would impede the draining of the sinks. Did you see a drain in the floor, was one one of the sink traps dry when you started, shower or tub drain dry? Did it have a mechanical or AAV vent on the line under the sink?

Outside of that I would take a SWAG that they cut the vent pipe off in the wall and left it open or it has a mechanical vent on it and it has failed.

Wouldn't the lack of a vent result in drain action pulling the water from the trap?

Marc

And the sink will burp, gurgle, etc...... Very very unlikely that the sewer gas will find its way up through the trap and sink while water is flowing down the drain.

[John Kogel]

Stinky water, maybe?

The water heater can cook up some ugly smells, and with both taps running, you can get a blast of it sometimes.

I'd recommend an AAV anyway. That is CYA and they won't bother to install one unless the drain traps clog up a lot.

[hausdok]

Hi,

It could very well be the water. Was the water heater turned off and left off for a long time before the inspection? When you turn off a water heater bacteria in the water is able to flourish and that bacteria starts to attack and feed off the anode rod. As it does so, the bacteria generates hydrogen sulfide gas and that gas forms a bubble in the top of the tank. Once you start drawing water off that tank the gas enters the house with the hot water and the smell is overpowering and smells exactly like sewage.

I did a cabin out on Hat Island about two weeks ago where the power had been turned off for weeks. There's no gas on the island, so folks out there have all-electric homes unless they have propane appliances. I fully expected that the water in the water heater would stink since the water heater had been turned off; but before I could warn the clients not to turn on the hot water until we'd had a chance to open up all of the windows, the husband did just that, cracked that hot water faucet. Gawd! He only had the tap open for maybe five seconds before he closed it, and I opened all of the windows and doors as fast as I could, but that smell remained for most of the inspection and dissipated very slowly.

They'll now be leaving the power on when they aren't on the island and will turn off power to everything except the water heater and will, per my recommendation, be installing a 24-hour timer on that water heater that will turn it on for about an hour every twenty four hours to cook off any bacteria so they never have to go through that again.

ONE TEAM - ONE FIGHT!!!

Mike