I'm sure this has been a topic many and far, but I have to ask again as many of the issues I've seen regarding this weren't completely answered. But...With my recent purchase of my new Class C RV, the previous owner left a holding "pyramid" (to put it lightly) that we could smell every so often when using the bathroom (primarily when we flushed, letting up all the stench).Well, I did a thorough flush, which involved a high-powered nozzle on the hose, through the open window, directly into the toilet (since we don't have a dedicated flush valve). After about an hour of filling the tank and flushing it out, blasting etc, the water finally came out clear!As an added bonus, the holding tank meter always showed "2/3 full", and after the deep flush it was showing empty, meaning we got out a lot of what was in there.I added chemicals per instruction (1 bottle of chemicals = 40g tank cleaning), with water as per instruction as well. (it is a 40g tank)That night, the same stench from before returned like a phantom. It was horrible, but we had not used the bathroom since we flushed it and chemicalized it. The tank still showed empty.Any earthly idea as to why it would still be stinking? It comes and goes, so I know it's not burned into the walls. We open the vent, close the door (toilet is sealed off with it's own door and room) and after 5 minutes it doesn't smell anymore. an hour later, a stink bomb comes back and we repeat step 1.ANY ideas whats going on? Tips, suggestions? I am knew at this but willing to try anything. I scouted the bathroom, took out the toilet and wall fixtures and there doesn't seem to be any issues. The stink comes in regardless if we're flushing the toilet (yes, there is about an inch or two of water in the toilet as a "stink barrier" per recommendations I looked at before.)Please help! (and thanks!)

Always ensure the house has either a neutral pressure OR a positive pressure to out doors before flushing the loo. In other words, if you have either a kitchen fan or a fantastic fan sucking air from inside to outside when you flush the loo this type of problem happens.And/or if it is a windy day and a downwind door or window is open, presto! etc etc

Harvard wrote:Always ensure the house has either a neutral pressure OR a positive pressure to out doors before flushing the loo. In other words, if you have either a kitchen fan or a fantastic fan sucking air from inside to outside when you flush the loo this type of problem happens.And/or if it is a windy day and a downwind door or window is open, presto! etc etcI made sure of this as well. Fan's off and (it being winter, super cold in northwest Texas, etc) the house is completely closed up. The stench also appears when not flushing as well.How would one check a blocked vent? Do we need to put water down the pipe or something? (which also tells me... I need to find where the vent is!)

I too would check for a blocked vent pipe..

Here's another path to go down, because it happened to me. It wasn't the toilet at all, but the stink was coming from the bathroom sink. Underneath our bathroom sink, there is not a vent that goes directly to the roof. But there is an "air admittance valve" which is a perfectly fine way to vent the plumbing. But our air admittance valve failed, and it was letting tank gasses come into the bathroom at all times. I could have sworn that smell was coming from the toilet, and accused my son of covertly eating pickled eggs and cabbage. If it is the air admittance valve on your sink, it's very easy to fix. Just unscrew it, and buy another one from Lowes or Home Depot for about $20 and replace it.

Bathroom stench after flush and chemicals | Good Sam Community

Bumpyroad
Explorer
Jan 18, 2015
Bobbo wrote:
Ramair wrote:
http://www.uniquedistributing.com/product_info.php?products_id=94

I have used this and its the best for controlling odors and when dumping everything is liquid. It claims it will remove the poop pyramid with 24 hrs.

http://www.uniquedistributing.com/product_info.php?products_id=94

Made clicky

at $19 a quart it better work.
bumpy
Jim_Shoe
Explorer
Jan 18, 2015
Check this first, before you spend money. If your toilet has two foot pedals, one opens the opening to the holding tank and one pumps water into the toilet to flush. After stepping on both pedals to flush and then releasing them, only push the pedal that lets water into the bowl. A couple of inches will keep the fumes from rising up into the bathroom. That may not be the problem, but if that's what's happening, its a free fix.
Bobbo
Explorer II
Jan 18, 2015
Ramair wrote:
http://www.uniquedistributing.com/product_info.php?products_id=94

I have used this and its the best for controlling odors and when dumping everything is liquid. It claims it will remove the poop pyramid with 24 hrs.

http://www.uniquedistributing.com/product_info.php?products_id=94

Made clicky
Ramair
Explorer
Jan 18, 2015
http://www.uniquedistributing.com/product_info.php?products_id=94

I have used this and its the best for controlling odors and when dumping everything is liquid. It claims it will remove the poop pyramid with 24 hrs.
hershey
Explorer
Jan 14, 2015
Does the toilet hold water between flushes? If it doesn't, then the odor will seep upwards and cause the bathroom to smell. And for goodness sakes, quit using chemicals. Your just adding yet another smell to the tank. 10 years of fulltime and never used any chemicals. Only time we ever get a smell is when the toilet seal fails to hold water in the toilet. Then its time to add some vinegar to the toilet and let sit, it removes the calcium.
rvdudes2
Explorer
Jan 14, 2015
Despite diligently and thoroughly cleaning our black tank we had the exact same stinky problem until we installed our Cyclone Sewer Vent. We haven't had any problems since.......
Pangaea_Ron
Explorer
Jan 13, 2015
Remove the cap for the roof vent, as others have said, the vent line could be blocked, but don't do what I did.

I placed a ladder beside the MH reached over and removed the cap. When it was removed, I could see that a wasp nest was blocking the vent, so I reached in and grabbed it with my bare fingers (without thinking). Fortunately the wasps were slow to react, and I was able to retreat down the ladder. I had the visual of me laying on my back in the driveway, bleeding, with the ladder toppled over me, and being stung by wasps.

A bit of wasp spray later, and a thorough cleaning, the smells were gone. I also installed a Venturi rotating vent cap to increase the draw.
CaLBaR
Explorer
Jan 13, 2015
jplante4 wrote:
kyonu wrote:
Thanks everyone for your quick responses! I will definitely check the AAV under the bathroom sink.

The smell only occurs in this space. It's worse with the lid open, and we typically will not smell it unless we open the door (as shown in the pic). If it's NOT the AAV, how should I go about cleaning the vent pipe?

Thanks again!

Climb up on the roof with a running water hose and stick it down the vent. If it's plugged, it will fill up and overflow. Jam the hose in as far as it will go, jiggle is around and when the vent drains you're done.

Yeah, you can do it with a snake, but this is much more fun. And you already have a hose, probably not a snake.

I had the exact same problem with the smell and did the hose water trick and voila no more stink. This is easy to do and if the smell is still there look further.
txdutt
Explorer
Jan 13, 2015
buy a flushking connector & backflush your tank since you don't have a flush fitting, you may have gotten rid of the "pyramid" but there's probably lord knows what still in there (yecchhh!!)
---another thing to try are enzymes---you can get them at any rv supply place--Rid-X might do the exact same thing---fill your black tank at least half full & put a few enzyme packets in there & let it sit for at least 24 hours & then dump/flush it out
coolmom42
Explorer II
Jan 12, 2015
Are you 100% sure you got rid of the pyramid?