Smell in camper when emptying tanks and flushing

[54Fun]

These are probably separate issues, but in case anyone thinks they are all related, I'll list them out:

1. I pull my gray tank (did not used to do this), and I've been getting a bad odor in the camper itself...it almost smells like black tank...but I know they gray tanks can get very stinky as well

2. I use my blank tank flush inlet, and I get the black tank smells in the camper. I've tried it both with the sewer closed, and open...same result of smells inside

3. I just dumped my black tank, closed the valve, then backwashed the sewer hose by opening my gray (as usual)...black tank smell inside!!

This is getting old (and smelly)...anyone have any advice?

I should also note a few things:
- A few weeks ago I did replace the sink air vents (one in kitchen sink, one in bathroom)
- I do routinely use conditioner & drop-ins for both tanks
- The smell primarily does not seem like it is coming from the bathroom/toilet...but really just outside of there in the rear wardrobe/bunkhouse area FR Vibe 308BHS floorplan
4. I also just posted this thread that my fresh tank is getting filled by my city water somehow...again, guessing it is not related, but throwing it out there. This is my last Forest River

[60sumtin]

Sounds like a blocked vent or vents. As the tanks fill the air in the tank has to exit somewhere. Have you checked the plumbing vents on the roof to see if they are clear?

[BFlinn181]

You said you replaced, "the sink air vents" I guess you're talking about AAV? (cheater vents) You also mention having black tank flushers. They have a vacuum breaker-check valve, often in a cabinet or closet. If that is faulty, it could allow sewer gas to enter the RV. I'd search for that and also AAV valves can be bad from the store, you might recheck them.

As to the water tank filling, it is one of two things. Either the city/fill selection valve is leaking or the water pump check valve is allowing water to go back up into the tank. Does your water pump cycle on when no water is used? That would indicate a leaking check valve. If not, then I'd suspect the city/fill valve.

[raineman]

If you have changed the air admittance valves with no change in smells, you may have a blocked vent pipe. When ours does that, changing the air admittance solves the problem right away.

[Power247]

We are having the same issue with smells in the camper after dumping. Is there a preferred AAV type/brand?

[BFlinn181]

Originally Posted by raineman

If you have changed the air admittance valves with no change in smells, you may have a blocked vent pipe. When ours does that, changing the air admittance solves the problem right away.

A blocked vent pipe can be tested by removing the cap and pouring water, from a bottle or a hose, down the vent. I don't think this is a common problem.

Originally Posted by Power247

We are having the same issue with smells in the camper after dumping. Is there a preferred AAV type/brand?

I'm not that familiar with AAV vent brands, perhaps just don't buy the cheapest?

[Bob_C]

Not only a Forest River problem......I did away with the plastic valve and 12' of extra hose and installed a house style double flapper backflow preventer.....vent pipe on roof is doing it's job......

[54Fun]

Thanks guys. Yes, I was talking about the cheater valve that I replaced by the sink drains. Dumb question...Is that the same as an AAV, or is that the one on the roof? I wonder if you’re on to something with the roof vent being blocked. My roof was recently replaced under warranty, and there is a whole lot of Dicor up there. I guess I need to figure out how to check those

[60sumtin]

Air Admittanace Valve, cheater valve, same thing. Do a google search and you'll see some images of them. In a home you'll often find them where kitchen sinks are installed in an island. In an RV, well its could very well be a short cut to save time and money. They are not the preferred way to vent because when they don't operate properly you get sewer gas coming in. Proper venting is non-mechanical and allows gases to escape to the atmosphere.

The roof vent likely has a removable cap on it to keep debris out. Take the cap off and have a look. A water test will reveal a blockage but not a restriction. While you have it off push a snake all the way down to see if there is perhaps a blockage. The purpose of proper venting is to prevent p-traps from being sucked dry while dumping or when other sinks or tub are drained.

[wingman8]

I found the vents plugged up on my RV with mud dobbers (wasp)

[1bigmess]

Are your windows open when you dump? Could just be the smell from a nearby sewer system vent coming in the window. I've stayed at at least two RV parks that have vents at the far end points of their sewage pipe system because they have a septic system instead of being connected to a sewer utility system.

[Rickho]

I never saw the smell as a venting issue. When I dump some smell does come in and has since it was new. Doesn’t the act of dumping cause a vacuum effect pulling air away from the venting? I would only be concerned if it was a constant smell under normal use which means you have blockage.
When I dump I open the bathroom sky light and turn on the exhaust fan to draw residual odor straight up and out.
When done I give the tank a thorough flush with the hose used only for the tanks and add 1/3 water back in to keep it functioning properly.

[egwilly]

I found a disconnected vent pipe to the grey tank the factory forgot to glue(or disconnected during travel).
It was inside the cabinets area so it was easy to fix.

[Rickho]

Ok, it’s worth checking into. Amazing what we get use to as being normal. Not the biggest issue in the world but worth a look. Thanks