Grey Tank Odor

[Chris Hewitt]

Having bad odor issues coming from the bathroom sink. We have been full time in our 2019 GD Transcend 28mks for almost 18 months and this is the first time. It started 2 days ago so we removed the p-trap under the sink and the shower and cleaned them. We treat all of our tanks with tank treatments so pretty sure that is not the problem. When we look using a flashlight there is water in the drain. Any suggestions. Thank you.

[Cate&Rob]

Chris Hewitt
Hi Chris . . . welcome to our owners technical forum.

Under most RV sinks is an AAV (air admittance valve) which is supposed to let air into the drain system, but not let air out. These valves do fail. Replacements are available at Home Depot or similar. I would start by replacing this valve. Usually only hand tightened into the threaded pipe.

Rob

[Chris Hewitt]

Thank you but we cannot find the valve. It is just the plumbing pipe with the removable p-trap section. Any idea where it would be or if we can find schematics on the plumbing system in our rv?

[howson]

Thank you but we cannot find the valve. It is just the plumbing pipe with the removable p-trap section. Any idea where it would be or if we can find schematics on the plumbing system in our rv?

Chris,
This is a pic of the AAV (red arrow pointing to it) under the bathroom sink on my 315RLTS. Is there not one of these in your Transcend?



Howard

[Chris Hewitt]

The p-trap disappears into the wall, there is no T. There is something that looks like that on the tube on the roof.

[howson]

The p-trap disappears into the wall, there is no T. There is something that looks like that on the tube on the roof.

You've got a closet in your 28MKS that's in the same location as the one in my 315RLTS. Assuming it has drawers like mine, if you pull them out there may be an AAV in that area. Here's what it looks like:



If it's not there I'm out of ideas...

I'll check this thread again in the morning.

Howard

[Chris Hewitt]

Thank you, we found it behind the drawers. That part you are pointing to is tight. Do you think we need to replace it? The RV Vacuum Breaker Check valve was loose and we tightened it.

[Cate&Rob]

Thank you, we found it behind the drawers. That part you are pointing to is tight. Do you think we need to replace it? The RV Vacuum Breaker Check valve was loose and we tightened it.

A leaking AAV is a common source of grey tank odors . . . and usually not difficult to replace.

Rob

[howson]

Do you think we need to replace it?

A "sniff test" should provide the answer to that one!

I haven't changed an AAV myself but as Rob has mentioned it is a screwed-on part so *should* be fairly easy to replace.

Excellent video by the "RVGeeks" on the topic (I learned from it):

[boyscout]

Thank you, we found it behind the drawers. That part you are pointing to is tight. Do you think we need to replace it? The RV Vacuum Breaker Check valve was loose and we tightened it.

This is the part that many people who've been through this recommend as a replacement. Not the least expensive, but a popular reliable part.

https://www.homedepot.com/p/STUDOR-1...0341/202275238

It was very easy to replace ours in the bathroom - just unscrewed by hand. The one under our kitchen sink is a lot tighter - it's going to need some persuasion, but it should not be glued on, it should unscrew.

Good luck.

[howson]

Cate&Rob (or whomever!) -- related to this thread (I hope): what's the difference between the AAV and the Hepco? I know there's three of the AAVs in my 315RLTS (kitchen sink, bathroom sink, and then the one near the hot water heater under the closet). There's also the HEPCO attached to the washing machine drain line.

Why not just another AAV?

[Cate&Rob]

howson

The AAV is a one way valve for air. The Hepvo is a one way valve for water.

Rob