Black Tank Question

[MiramarTN]

We are on our first trip and after a couple of days camping, I emptied my black tank and ran the black tank spray wash. That was followed by emptying the gray water tank to help clean the sewer hose. Exactly as I was instructed.

Now we get a blast of sewer gas every time we flush the toilet.

Is this normal or did I do a newbie mistake? ….or has a malfunction occurred within my black tank system?

Suggestions appreciated.

[Yvonnemarc]

Make sure both the black tank and gray tank gate valves are closed tight. Close the lid when you flush. Running the bathroom fan? It'll draw air from the most direct route...the crapper. Check the plumbing vent on the roof so it's not plugged, when you flush the air in the tank gets displaced...usually up the vent.

[Miramar Owner]

Never run your vent fan while flushing the toilet or it will suck the sewer smell from the tank. After flushing you can use the ceiling vent fan for 30 seconds or so to vent your bathroom.

[Trkyte@msn.com]

Use a RV toilet/black tank treatment every time after you finish dumping. Helps with breaking down the paper and smell.

[Dilley-Dilley]

Also make sure you flush the tank really good with the specialist ff system. I usually flush each of my black tanks 3 times. When you use the sprayer system close the black tank dump valve and let some water get in there in case there are some stragglers. After you get a clean rinse then finish it off with the grey water to flush the hose. I always also use the sprayer system to put some water in the black tank and then add some enzymes to that from the toilet. Lastly, always check to make sure the dump valves (gate valves) are closed before removing the cap. The fan tip is a good one! ☝️

[SuperD]

Your roof vent could be fully or partially plugged not allowing the tank to vent properly.

If your bathroom sink dumps into your black tank, and many do, the air admittance valve may be loose, ours was. Open up the sink cabinet and look at the drain pipes, you will see a “T” that has a black piece sticking up about 4” tall, it screws in place. Unscrew the valve, wrap the threads with two layers of Teflon tape and screw back in hand tight. Our valve was only screwed in loosely with no tape and it allowed smell from tank to escape and really stink up the bathroom until I tightened it up. There is one under the kitchen sink you might want to check too!

[JamieGeek]

In addition to all that: If your vent is plugged, the air admittance valve isn't working and your bathroom sink also drains to the black tank perhaps the process of dumping sucked all the water out of the P-trap of the bathroom sink. Have you ran any water through the sink?

[Bob Denman]

http://www.thorforums.com/forums/att...1&d=1533817463

[Hooligan2]

Miramar-- Sounds like you did not have this problem before emptying the tanks...Are you still hooked up to the sewer system and have the tank valves open?? You may be importing the odor..

[MiramarTN]

The bathroom vent has one of those insulator pads inserted so no air being pulled through there. I looked under the bathroom sink. The P-Trap has no extensions other than to exit the sink cabinet toward the shower drain.

We have run the sink faucet many times so the sink P-Trap isn't empty.

Based on your ideas, it sounds like it could be vent pipe related.

In addition to the hot and cold water supply lines that come up to feed the bathroom sink faucet there is a cold water line that connects to a black fitting/box that then connects to a white line and exits through the same entrance hole. Could this be related to the vent pipe like SuperD & JamieGeek were suggesting?

Thanks for your suggestions.

[JamJanTan]

When we took our first couple of trips there was a smell in the air. It cleared up after a few more trips. Hope yours does the same. Sometimes you get a smell depending on where you are camped. But if it is just when you flush that it blasts you in the face it may be a problem that needs more than time.

[Bob Denman]

We added a pair of these to our roof; in order to coax the gases out ...

http://www.thorforums.com/forums/att...1&d=1533851897

[The Gritz Carlton]

Bob, I like that! What's the maintenance on the bearings/swivel part of that device. Does it have an oil port? Does it swing around easily? I could see it getting seized up in the wrong wind direction maybe?

[MiramarTN]

I drained the black tank again and let the tank wash run for a good 5 minutes. I had not left the tank valves open. I won't swear it helped but it didn't seem quite as bad. I didn't see the bubble come up from the black tank as often.

I read on another thread about problems with right hand toilet like I have on my Miramar 34.2. It suggested the black tank is shallow and so I guess wide. The dump is on the left side of the MH and the toilet pipe appears to turn toward the left side of the MH so this sounds correct. That thread suggested pouring 5 gallons of water into the tank to help lubricate the system for flushing. I hear gurgling sounds coming from the toilet. I wonder is there is a clog in the pipe that is not allowing the waste to flush smoothly all of the way to the tank and my odor is coming from that clog.

I am home now and am going to get a bucket of water and try to flush the line to the tank. I will drive to the RV park down the street and do a final tank dump later today.

There were a few other items that popped up on the trip for a little more warranty work to be done. I will ask them about this as well.

Bob, I can see how your vent cap would develop a vacuum and help pull sewer gas while moving down the road but does it help while parked? I know Thor is promoting the 360 degree vent caps on the 2019 models and am thinking about having the dealership install while they are doing the warranty work.

[Dilley-Dilley]

Letting the black tank fill up sufficiently between dumps helps to get some head pressure for stuff to flow. When running the flush system it really helps to keep the gate valve closed to also get everything possible to float as well as build up a little head pressure. The way the black tanks on my Miramar 34.1 are designed they are long with a gradual incline from the passengers side of the coach that flows into a deeper sump on the drivers side where the dump valves and plumbing are.
The layout of the black tanks works better for the toilet on the drivers side of the coach because it is directly above the deeper sump portion of the tank. That puts the heavier waste where it needs to be in order to be dumped out.
However, The toilet on the passengers side of the coach is positioned over the shallowest portion of the black tank furthest away from the dumping valves and plumbing. Since that’s the case the heavier waste is potentially entering on the dry end of the tank and that will likely keep it from flowing down to the sump until there is sufficient waste built up in the tank. That’s why it helps to let the level build up and do some good tank flushing.

[Bob Denman]

Originally Posted by The Gritz Carlton

Bob, I like that! What's the maintenance on the bearings/swivel part of that device. Does it have an oil port? Does it swing around easily? I could see it getting seized up in the wrong wind direction maybe?

There's Zero maintenance, and I'm always prepared for "Shark Week"!
I'm not sure why they spin so freely: they just do!

[SuperD]

These 360 roof vents work great, easy to install, and have NO moving parts!

[MiramarTN]

Pulled out my garden hose and ran it into the MH toilet with my HD Homer bucket in hand. Poured a couple of buckets of water and the sprayed the water hose down the toilet. Leaving the flush valve open produced no sewer odor. Problem solved (I hope).

Next trip I will make sure I dump water down the line before use.

[JamieGeek]

Another way to solve the problem, albeit an expensive one (~$500), is to replace that toilet with a macerating toilet. Then it wouldn't matter what you put in the toilet it will be liquefied before going to the tank.

Hello fellow Chevy Bolt owner !

[MiramarTN]

Originally Posted by JamieGeek

Another way to solve the problem, albeit an expensive one (~$500), is to replace that toilet with a macerating toilet. Then it wouldn't matter what you put in the toilet it will be liquefied before going to the tank.

Hello fellow Chevy Bolt owner !

Love the Chev Bolt. I put 100,000 miles on my Leaf before I traded. Big upgrade.... (opps… I am on the wrong website for this post)