Sewer smell - only when flushing

[Newcsn]

In the last couple weeks our 2006 Dynasty is occasionally experiencing a terrible sewer smell only when flushing the toilet - have never experienced it previously. I know there are air admittance vents under each sink. Do these have anything to do w/ properly venting the black tank or are they all for the grey tank? We have a black tank rinse feature & use it every time we dump - and also add the orange Camco black tank odor pouches.

Thank you!

 

[Ivan K]

It happens when the toilet fan is on and all the coach windows and vents closed. It has nowhere to suck the air from than from the black tank when flushed or if the seal failed.

[Dr4Film]

Try Happy Campers tank treatment.

[vito.a]

Many of our coaches have sat on a dealer lot or had a previous owner that did not rinse the tanks. 

I use Blue Dawn platinum dish soap.  We get the large size from Costco.  Add it with water to the tank.  Let it sit overnight and then drain/rinse.  Rinse and repeat.  If you can drive it in between even better.  

You should also check the roof vent for the black tank.  

 

Edited January 8 by vito.a

[Bill R]

48 minutes ago, Newcsn said:

In the last couple weeks our 2006 Dynasty is occasionally experiencing a terrible sewer smell only when flushing the toilet - have never experienced it previously. I know there are air admittance vents under each sink. Do these have anything to do w/ properly venting the black tank or are they all for the grey tank? We have a black tank rinse feature & use it every time we dump - and also add the orange Camco black tank odor pouches.

Thank you!

 

The air admittance under sink vent (Studor Vents) do not have anything to do with the black tank roof vent.   Separate systems.  If the under sink vents are not sealing, when you flush the toilet, especially if you have the bowl filled with additional water in it, I believe you can create the slightest amount of negative pressure in the toilet room that allows some of the grey tank gases into the room through the sticking Studor vent.  And you will smell it as the grey tank is smelly as well.  Maybe, maybe not, but I had this problem and replaced the Studor vent, which I found was sticking, and it eliminated the smelly gasses after I flushed.  So try replacing the Studor vent and see what happens.  That will answer the question.  Otherwise, others have made some really good suggestions as well.

[Martinvz]

The ceiling fan could draw the air from the sewer pipe. This may be aggravated by a partially blocked black tank roof vent. Only inspecting the vent will determine if this could be the culprit.

[Newcsn]

This group is amazing - thanks so much for the feedback/suggestions on how to deal w/ our occasionally stinky situation!

We installed a new Lippert 360 Siphon Vent this summer. And, I'm having a hard time getting my head around the flush valve seal leaking - the toilet bowl never loses water & the smell is a very occasional occurrence (there seems to be no correlation to open windows or vent fans).

Just for grins (and b/c our coach is 18 yrs old & they're so reasonable), I'm going to replace all 3 air admittance valves. We're also going to start using the Blue Dawn Platinum in the tanks. Hopefully this resolves it!

Thanks again!