Black tank odors

[beaudin12]

We purchased our motorhome used last October, in January we had our black water holding tank professionally cleaned. The fumes and odors are still coming into our motorhome even right after we dump. The odors are present every time we flush or even just open the toilet valve. When I dumped last time the gray water stopped flowing, when I lifted the hose to allow what was in there to finish dumping the hose filled up again and then dumped the rest of the gray tank. My question is this could my vent pipe be blocked or is it something else?

[rockhillmanor]

Check the vent pipe on the roof anyway. It is supposed to have a cover on it. It is only held on by small clips. these get knocked off easily by tree branches when pulling into a CG site. And then stuff CAN go down the pipe and lodge.

[Lynnmor]

Turn off all exhaust fans when flushing. If a fan can be reversed so that it blows into the RV, that would help.

[dougrainer]

If you had the BLACK tank flushed and deodorized. AND, you do use chemical in the Black tank, the odds are your odor is NOT Black Tank odor but Gray Tank odor. Especially since you seem to have a problem when dumping the Gray tank. Gray Tank odors are a much more horrible than Black tank odors. As I have suggested on other threads, fill and flush BOTH tanks. Put your chemical in the Black tank and add about 5 gallons of water. Then put a pint of PINE SOL thru the kitchen or lavy sink. That will get to the Gray tank. Then do your dumping and see if you get the pine sol smell instead of that horrible odor. If so, your problem is a buildup in the Gray tank and you need to fill and flush it numerous times and then fill full and use a Gray tank chemical and let sit for a few days or a week and then flush numerous times again to get rid of that build up. Doug

[1492]

Moved from Forum Technical Support

[Walaby]

x2 on probability of it being the vent valve. On my 2014 Tracer, I had really bad odor. Replaced the vent valve and by next day, all clear. Which I was eternally grateful for, because the odor started right AFTER I decided to trade it in on my new 2016 Lacrosse. Was worried it was something bigger and gonna cost me a chunk of change. $6 at the local Lowes and I was good to go.

Mike

[Trackrig]

I doubt if it's the vent. It's made of 1-1/4" plastic pipe. Dirt or dust won't clog it and it's too small for anything to build a next in - maybe a spider could. We were having odor problems also. Here's my cover removed because someone insisted I go check it.



Look above at downtheroad's diagram. Right in the middle of it are two ASTVD vents. We have three of them and one of them was bad. I changed all three. In reading one of the vent mfg's web sites, they said they usually last ten years before they go bad. So Rather than playing guessing games as to which one was bad and then wondering when another would go bad, I changed all three. They are threaded, just unscrew them to remove them.



This is the sink that gave me a lot of problems. The vent was within a 1/4" of the sink bowl. I went to HD, Lowes, and a couple of plumbing stores. All they had were ones with larger diameters and therefore wouldn't fit. They fit on two of the sinks, but not the third one. It took a lot of driving around to find a small diameter one at an RV shop.

So find your vent valve(s), see if you have room for larger ones, take one off and take it with you to the store.

Bill

[downtheroad]

Yes, VENT PIPE would be the first place I would be looking...
Climb on roof with a hose and run some water down from the top. Make sure your dump valve is open when you do this.

If the pipe is not clogged, then it may have detached from the top of the tank and be pushed too far down - thus not venting and allowing odor to escape. (This will be a much harder fix.

Note: you are keeping the valves closed until you are ready to dump, right? Do not leave them open full time.