Black Tank Odor

[twogypsies]

OP: When you get it out of storage make note if the smell is there before turning the key or does it appear when you start driving. Are ceiling vents open or closed?

[shootist]

It most likely is the backflush valve , usually under the sink. When you backflush they seal, they are an air break so black water cannot go back into the city water system. Mine had a hair in it and that's all it took. The hair came from me using a garden hose I used for grey water to backflush with. New valve 60.00 new hose, new valve went bad in a few months, smell was back. Replaced it with a made up pvc 90 and no more problems. Put a shut off valve at the flush hookup and open it and close it under full water pressure if you flush with any potable water source.

[Steve 716]

Four things come to mind.

First, fill your blank tank 1/2 to 3/4 full. Open your campsite water valve and gate valve for your black hose outlet and let it run until you see clean water coming out, then keep it running for another half hour. Do this every time you dump. The object is to see an empty reading on your level monitor along with no smell. Sometimes I empty my tank and the monitor says as high as 36 percent even though it's empty. Two or three extended rinses bring it back to zero.

Second, when you are parked for a week or more put some Rid-X into your tank. Repeat at your next stop. It will eat away at the solids and clumps in your black tank given enough time.

Third, identify where in your RV the smell is coming from. You have more than one bathroom and other cabinets with PVC plumbing inside. Most or all of them will have an air vent mounted at the highest point in the plumbing. Remove the vents and install a Studor brand air vents in their place. Make sure they are mounted at the high point in the cabinet. There should be vents in each bathroom cabinet, the laundry area if you have one, and under the kitchen cabinet. All have air vents. The smell will be coming from one of these. When they no longer fully open or close the stinky air can escape from your tanks into your coach. Several years ago I had a minor odor in my mid bath and it was caused by the cheap air vents installed at the factory. After all of the vents in my coach the problem never returned. This likely is your problem and it's probably the vent closest to your black tank.

Fourth, don't forget to drop a treatment pack into your black tank after you have drained it. It won't hurt to drop two in if needed. I use TST packets but all of them are probably just as effective.

Studor vents come in different shapes and sizes so measure before you travel to Home Depot.

[Rogan72]

Had similar issues. Installed a turbo vent cap and problem went away.

https://parts.unitedrv.com/collectio...-plumbing-vent

[DJsAllie]

I'm probably a bit late on this but just saw it. We've experienced similar issues and did all that you stated. It was recommended we get the CLEAR part that goes from sewer hose to dump so we could visually observe the water was CLEAR. The first time we did this, it took 4 3/4 fills and then dump before it was clear. Then I stopped using a lot of the commercial products and went to a solution of 1 cup Calgon Bath Oil Beads, 40 oz. bottle Pine Sol in a gallon jug, filling the rest of the gallon with water. Be careful because it suds up BAD so, carefully, turn the gallon jug around a few times and put 1 cup in the now-closed black tank. Dump every 2-3 days if possible and can add a cup each day if needed. One thing it does is help to keep the sides of the tank slippery so solids don't stick. Now, this may not be for everyone but since we started, have not had any serious odor problems. We put about 10,000 miles on ours a year including living in it several months in the winter. Hope this helps. I find this info several years ago on a site where a fellow actually cleans out and repairs black tanks!

[twogypsies]

We full-timed 16 years and never used an additive. Dumped when full. Never any smells.

[nancyinj]

We had an ongoing odor in our 2020 FR3 32DS Dometic 300 toilet. Couldn’t find the cause. Called Dometic and were told they had a non advertised recall on the 300. They said they would replace the toilet for free and we could make arrangements to have it replaced locally. Problem was we received little to no assistance from the local RV center and they wanted to charge us to make the change. So, we upgraded to the 310, for $75.00, porcelain toilet, and will install it ourselves rather than pay the charge for installation to the center. Worth looking into.

[Jlo222]

It’s time to have the black and grey tanks professionally cleaned

[Jlo222]

Originally Posted by tdelong

We bought our Class C in December of 2020 and take it out about once a month all year long (we live in Texas). However, we are having issues with our black tank odor. We use Happy Camper, LOTS of water, and flush the tank 3-4 times every time we dump, then load it back up with water and Happy Camper. When we pick it up from storage, it's fine. After one day of use, it smells like an outhouse - no matter what we do. We've checked the vent, by sending water from the roof, and it lands in the tank with no visible leaks. I'm at a loss as to the problem, and we are taking a three week trip in July. I can't live with an outhouse smell for 3 weeks.
Any suggestions about what I could be missing? Or another way to check the vent? I'm afraid that it is venting into the bathroom, but I thought our trouble-shooting measure proved the vent was functional. Help and advice would be so welcomed.

It’s time to have the black and grey tanks professionally cleaned

[Jlo222]

Originally Posted by tdelong

We bought our Class C in December of 2020 and take it out about once a month all year long (we live in Texas). However, we are having issues with our black tank odor. We use Happy Camper, LOTS of water, and flush the tank 3-4 times every time we dump, then load it back up with water and Happy Camper. When we pick it up from storage, it's fine. After one day of use, it smells like an outhouse - no matter what we do. We've checked the vent, by sending water from the roof, and it lands in the tank with no visible leaks. I'm at a loss as to the problem, and we are taking a three week trip in July. I can't live with an outhouse smell for 3 weeks.
Any suggestions about what I could be missing? Or another way to check the vent? I'm afraid that it is venting into the bathroom, but I thought our trouble-shooting measure proved the vent was functional. Help and advice would be so welcomed.

Time to have black & gray tanks professionally cleaned

[Lynxman]

Professionally cleaned tanks!!?? Do it yourself, it's simple.
Go to your local hardware store or rural grocery store and buy a package of "Septobac" or some other septic tank treatment. Fill the tank with water, add the septic tank treatment, let it sit for a week or more (the longer the better) and after you drain it, if you can see directly down your toilet into the black tank with a flashlight the reflection from the sparkling clean tank will shock you. It did for me when I used that to clear up a partially plugged black tank.
The septic tank treatment releases millions of "Professional" microscopic bacteria that consume all of the things that you put into your black tank and the beauty of it all is that once you buy the treatment, the bacteria work for FREE!

[Gforceone]

Do not have bath fine ON While you are using and flushing the stool. Turn it on, after flushing. Otherwise it will pull odors up when flush valve is opened. EASY PEEZY FIX 😁👍

[Barneyb]

Believe it or not most every tank smell we had was from the grey water tank not the black water tank. Not saying this is your issue but worth a check. I use Tank Blaster in our grey water tank.
Best of luck

[garywilson]

Originally Posted by Rogan72

Had similar issues. Installed a turbo vent cap and problem went away.

https://parts.unitedrv.com/collectio...-plumbing-vent

me x2