This reader question was answered by RV technician Chris Dougherty when he served as the technical editor of RVtravel.com.
We’ve been stationary for almost a month, so far. I’ve noticed what I think is a pyramid formed at the pipe base in the black tank. This has occurred twice in two weeks. I use one of those magic wands to clear it. We use probiotics in all tanks and Scott toilet paper. I use the flush king after every emptying. Any thoughts or suggestions? —Alan
This is a common problem, and you’re fortunate that you can actually see into your tank, as many RVers can’t. The problem is a result of too little water in the black tank. This can be an RVer’s error, or it can be a malfunction.
When it comes to sewage, water makes the world go ’round… and the sewage go down. For some people, they use no extra water in the holding tank because they are afraid to fill it up too quickly, especially if they’re dry camping. Others, especially if they’re on a seasonal site, leave the black tank valve open all the time, thinking everything will just drain, and it doesn’t…causing a buildup of sludge. Some folks won’t use chemicals, which can also do the same thing.
From the malfunction standpoint, the black tank system could have a leak. It could be as simple as a poorly sealing termination valve, or it could be more serious, like a cracked tank, or a failed pipe connection at the tank. If the tank has failed, there will be signs of leakage and odor. If your unit has an enclosed underbelly, there should be staining where the liquid has drained, and sometimes pooling which will weigh the underbelly enclosure down causing it to bow.
Finally, if the leak is in the valve, and this is the most common malfunction, it will be obvious when the cap is removed from the termination to dump the tank after use. If you are leaving your hose connected all the time, then there will be no sign of this, of course.
This is often caused by one of a couple of things: there is some stuff jammed in the o-ring part of the valve, the o-ring has failed, or the valve is in need of lubrication to make it close properly.
The best way to fix this is to service the valve, especially if it has been in use for a long time. To do this, disassemble the valve, clean the parts, replace the seals (available on Amazon), reassemble and lubricate using Dow Corning 111 valve lubricant.
Hope this helps!