Help, please! Sewer smell

[Rene T]

That’s awesome. Thanks for getting back to us. It may help someone down the road

 

[JudyJB]

One other thing I occasionally do is to dump my black tank and then fill it a third or half full of fresh water and maybe some soap and a cup of bleach. Then find a nice, empty road out in the country where you can do whatever it takes to slosh things around. Maybe some hard stops. And also try swerving back and forth. The latter is why you need a nice empty road so people will not think you are drunk or crazy. Do this for maybe 15 minutes, then drive back to campground and dump your tank again. Maybe even add a couple of gallons of fresh water inside or using your outside flush hose--the object is to try to get stuff out before it dries.

This will help remove any gunk and toilet paper that is stuck to the walls and bottom of your tank.

Also, a very slightly open vent in your bathroom or living area might help sewer gas from being sucked into your RV.

 

[TXMOOSE]

I had no idea where this was going but was interested since I never had the issue. I myself am curious why that effects the AC like that or even the inside. But I'm glad you found a solution and posted it. You are now the King RV tech.

 

[TXMOOSE]

Wait , not sure but if the AC that catches the smell is near the Crack below then as ACs catch and circulate the air I guess maybe that is what it was doing .

 

[Claassen]

One other thing I occasionally do is to dump my black tank and then fill it a third or half full of fresh water and maybe some soap and a cup of bleach. Then find a nice, empty road out in the country where you can do whatever it takes to slosh things around. Maybe some hard stops. And also try swerving back and forth. The latter is why you need a nice empty road so people will not think you are drunk or crazy. Do this for maybe 15 minutes, then drive back to campground and dump your tank again. Maybe even add a couple of gallons of fresh water inside or using your outside flush hose--the object is to try to get stuff out before it dries.

This will help remove any gunk and toilet paper that is stuck to the walls and bottom of your tank.

Also, a very slightly open vent in your bathroom or living area might help sewer gas from being sucked into your RV.

I’ve heard dumping ice into the black tank before you pull out to travel also helps clean the tank. We’ll be sure to do this when we pull out.

 

[Claassen]

I had no idea where this was going but was interested since I never had the issue. I myself am curious why that affects the AC like that or even the inside. But I'm glad you found a solution and posted it. You are now the King RV tech.

Hahahaha! It still doesn’t make sense to me, but I’m glad it was something simple. Definitely not a tech, but if me posting the solution helps someone else I’m happy.

 

[TXMOOSE]

Well like I said , I wonder if from the Crack in your hose if the smell was going through that AC unit and possibly causing the stink during the flush. But I'm glad it's settled it's just not what ya look forward to with you OJ and bagley, I've heard of everything bagles but that's to much.

 

[HueyPilotVN]

The hint about putting a bag of ice cubes in the black water tank works best if you put it in before you drive and slosh it around to loosen the stuff on the sides of the tank.

Maybe even add some soap at the same time.

Stop, start and shake it up with a few turns for the best results.

Then dump it.

Putting it in and dumping right away or letting it melt before sloshing it around does not work as well.

 

[Claassen]

The hint about putting a bag of ice cubes in the black water tank works best if you put it in before you drive and slosh it around to loosen the stuff on the sides of the tank.

Maybe even add some soap at the same time.

Stop, start and shake it up with a few turns for the best results.

Then dump it.

Putting it in and dumping right away or letting it melt before sloshing it around does not work as well.

That’s what I meant. I probably didn’t explain it well. thanks for the clarification.

 

[Kirk]

That’s what I meant

It is far more effective to fill the tanks 1/3 full and then add some laundry detergent before travel and then dump when you arrive. Ice melts very quickly so is a poor answer, especially in hot weather. The other issue is that it is very difficult to get ice cubes into the gray tank but water and detergent get there quite easily.

 

[Laura & Charles]

Resurrecting this thread as we are now having this issue (black tank odor coming inside via the A/C vents. Our issue happens only when the black tank is about 1/3 (or more) full. We usually dump on day five. On day three the smell starts coming in. We have two toilets and the smell comes when flushing either of them, but a little less strong with the macerating toilet. Turning the A/C off before flushing eliminates the issue. We have three A/Cs (ducted together) and the smell comes in if any of them is running, but the smell is strongest in the bedroom. But is certainly noticeable from all vents. And it is definitely coming through the vents; just stronger toward the rear of the coach. (So the smell is strongest where the macerating toilet is, but also strongest when flushing the other (gravity) toilet.). Haven’t tried yet, but I assume when heating with the heat pumps the problem will remain.

OP said it resolved with replacing their sewer hose. Did that last week and today is the third day since last dumping and the smell is back.

 

[Gary RV_Wizard]

By design your a/c's do NOT bring in outside air - they only recirculate inside air, so something is very wrong if they are somehow picking up odor from the roof area. More likely you are getting the odor inside and the rear a/c is picking it up a distributing it. I'd be looking around both toilets, and also looking at gray tank sources, e.g. the air admittance valves under the sinks.

 

[Kirk]

We have two toilets and the smell comes when flushing either of them, but a little less strong with the macerating toilet.

This seems to indicate that the odor is when flushing, and that means up the line from the black tank through the open toilet line. I would think that Gary's theory is probably right.

 

[Henry J Fate]

You have 2 toilets and one black tank ? Both toilets are sitting over the tank so that waste drops vertically into the tank ?

There is only so many places that black tank odors can escape. Each toilet flange is supported by a tank seal which seals the pipe entrance to the tank. The vent from the black tank to the roof also has a seal where it enters the tank. If any of the 3 tank seals leak, the odor will get under the floor and travel from space to space. Check to see if you can get a sense of any odors in storage compartments and any other space below the floor.

There are 2 more seals. 1 at each toilet flange. Those seal the toilet to the flange. Those should be air tight.

All the piping used should be glued properly. The roof vent is the pipe I would suspect first. Its a long run and sometimes is not a straight shot to the roof.

 

[Laura & Charles]

You have 2 toilets and one black tank ? Both toilets are sitting over the tank so that waste drops vertically into the tank ?

There is only so many places that black tank odors can escape. Each toilet flange is supported by a tank seal which seals the pipe entrance to the tank. The vent from the black tank to the roof also has a seal where it enters the tank. If any of the 3 tank seals leak, the odor will get under the floor and travel from space to space. Check to see if you can get a sense of any odors in storage compartments and any other space below the floor.

There are 2 more seals. 1 at each toilet flange. Those seal the toilet to the flange. Those should be air tight.

All the piping used should be glued properly. The roof vent is the pipe I would suspect first. Its a long run and sometimes is not a straight shot to the roof.

The macerating toilet pumps what it macerates to the black tank. The other (gravity) toilet drops straight into the tank. And yes, just one black tank. The odor is definitely entering the coach via the ceiling A/C vents.
.

 

[Laura & Charles]

This seems to indicate that the odor is when flushing, and that means up the line from the black tank through the open toilet line. I would think that Gary's theory is probably right.

I know better than to question you or Gary, but what baffles me is, why does odor only get distributed when the tank is 1/3 full or more?

 

[Henry J Fate]

The macerating toilet pumps what it macerates to the black tank. The other (gravity) toilet drops straight into the tank. And yes, just one black tank. The odor is definitely entering the coach via the ceiling A/C vents.
.

You have a single ac unit or 2 units ?

The odor at the vents would have to originate on the intake side of the system which is physically between the intake filter grille and the blower. Not a large distance at all. Probably less that 2 feet. If the odor exits the vents just at start up and not continuous, then i guess it is possible that the odor is migrating into the ceiling ducts when the system shuts down and then blowing into the living space once the system calls for ac.

Being 1/3 full is maybe just a biological boundary that hits an odor volume level that becomes noticable. Things do ramp up as the volume increases. There could be a physical reason for it like maybe the macerator starts turning things up at a certain point.

Looking for the cause is best done when HVAC is off.

 

[ferfer]

Henry J Fate per original post #31 three air conditioners.​

We have three A/Cs (ducted together) and the smell comes in if any of them is running, but the smell is strongest in the bedroom. But is certainly noticeable from all vents.

 

[Kirk]

why does odor only get distributed when the tank is 1/3 full or more?

That is difficult to say but it might be that your empty tank doesn't generate much odor, or if you use a tank chemical the perfume works until you get that much in it. There is another, more challenging thing that may will be the cause, which just crossed my mind. The waste tanks have a vent line that extends up through the roof of the RV where there will be vent caps over them to keep out rain. If the pipe that runs between the tank that the vent cap is not well attached they have been known to slide downward into the tank. One the end of the vent pipe is covered by liquid, the air can no longer fent out through the roof as designed and so when you flush it will push a puff of air up and out of the toilet. If that is the case, you can probably feel that air by holding your open hand, palm down and at the top of the bowl while you flush. If that is the problem, you should be able to go to the roof and remove the vent cover and snag the pipe and pull it back up. This is not a rare problem. Most waste tanks are wide and shallow so that it doesn't have to slip down that far. I have seen very few RV waste tanks that were more than 10-12" deep so if the pipe normally extends 2 or 3" into the tank and it slips down 3" the problem will begin. A slip of 6" will cause that sort of problem in most RVs. When I experienced it in a previous RV, I realized where the odor was coming from one day when the tank was half or more full and I flushed before I stood up from the toilet.