Foul smell in toilet - caused by air admittance valve? Is this normal?

[katheh]

I have a foul smell in downstairs toilet which also contains a sink and washing machine. Checked the drains outside and everything is flowing well. I suspect water might be being sucked out of the traps for the sink and washing machine. I also investigated what was boxed in under a corner shelf and found the air inlet pictured. Is it normal to have something like this within a room? Could this be the cause of the smell if stuck open or closed?

There is a loft space above so I'm wondering if it would be better to run this pipe and air inlet up there.

I should add I have been living here smell-free for 7 years. This room is in an extension added 8-9 years ago.

Thanks in advance for any help.

Air Inlet

• katheh
• 1 Dec 2020

 

[Hugh Jaleak]

Clue is in the name with those things, Air Admittance Valves, designed to let air into the system when an appliance is discharged. If it's stuck open, then there lies your issue, it should close again once it's done its job. Normal practice to install internally, ultimately that's what they were designed for, although external versions are available.

Options are, and assuming you have another open vent stack on the property somewhere to ventilate the drains, repair that AAV, if that's not feasible, replace it. If you really want to, you can continue the stack upwards, but could have the same issue in future if the valve fails again, and stinks the loft out. Only you wont notice so easily I suspect.

If there isn't another vent, then you seriously need to look at fitting one somewhere convenient, drains need to breathe too.

 

[katheh]

Thanks, yes, there are two others outside extending above the roof line. They are connected to the drains from 2 upstairs bathrooms. Those two drains and this one from the toilet connect together underground at the front of the house. The drain from the kitchen has no air inlet but possibly because there is no toilet?

 

[Hugh Jaleak]

A toilet can connect directly to the drain, under certain circumstances, but common practice these days seems to be to fit an AAV as well. Sinks etc are fine on a direct connection to the drain.

As you've already adequate ventilation elsewhere on the system, you should be fine just to repair or replace the faulty AAV.