Blackwater tank

The original post was about using a "vented" cap in winter! You might try reading the entire thread.

You can try "tissue digester" follow directions on container. I believe this can be bought at Camping World or any RV store that sells supplies and etc.
I have heard others have had good luck with this. Mostly from people buying used trailers.

Ice cubes has very limited results.

Allworth wrote:
During typical winter storage, the tanks are 90% air and 10% liquid (at most).

Water expands 2.2% on freezing. Bad in a closed bottle or pipe, but...

The tank is now 97.8% (compressible) air and 12.2% ice. Even if the air were not vented through the roof, there would not be enough pressure difference to hurt the tank.

That makes sense, but I've seen an open bucket crack with a couple of inches of ice in it. Apparently it expands in all directions. This doesn't make sense to me. If it tries to expand and meet resistance, wouldn't it expand in a direction it could?

Allworth wrote:
During typical winter storage, the tanks are 90% air and 10% liquid (at most).

Water expands 2.2% on freezing. Bad in a closed bottle or pipe, but...

The tank is now 97.8% (compressible) air and 12.2% ice. Even if the air were not vented through the roof, there would not be enough pressure difference to hurt the tank.

NOTE: This is only about tanks during normal storage; not full tanks, water heaters, pipes, toilets, or faucets.

Another solution is to move to Florida, park it in the back yard, and forget about winterizing.

What in Gods name does this have to do with the dreaded pryamid of dung? Am I missing somethig here?

During typical winter storage, the tanks are 90% air and 10% liquid (at most).

Water expands 2.2% on freezing. Bad in a closed bottle or pipe, but...

The tank is now 97.8% (compressible) air and 12.2% ice. Even if the air were not vented through the roof, there would not be enough pressure difference to hurt the tank.

NOTE: This is only about tanks during normal storage; not full tanks, water heaters, pipes, toilets, or faucets.

Another solution is to move to Florida, park it in the back yard, and forget about winterizing.

Are you certain the advice was to let the black open and not the grey? Not that it matters now..

You can use Liquid Drano. Our owner's manual says to use it. Put some in along with say 5 gallons of water and go tow it around for a while then dump the contents. When dumping, never dump it into a private on-site septic disposal system as it can cause serious damage to it. We've used it twice now and it returns your tank to clean and shiny inside like it was at the factory. Also gets rid of false readings.

Dtaylor wrote:
I dont know how yours is, but in mine, the toilet sits directly over the black tank. I can open the toilet and see the bottom of the tank. If your is like this then you can break it up manually.

This isn't always the case with different brands of RVs. My old RV had an elbow below the toilet going into the tank. No way I could manually break up the pile. If the OP can do this then that would be very helpful.

Back in '03 I purchased a 2 year old 5ver and the previous owners didn't understand how to use their black tank valves either. I tried the ice, but don't think it did much good. Over the 12 years that I owned the unit I always put some liquid Calgon into the water I used prior to heading out for a camping trip. I put the deodorizer in and then dumped about 2-3 gallons of water (with the Calgon) into the tank. I think that this eventually dissolved the "Great Pyramid" in my black tank.

I dont know how yours is, but in mine, the toilet sits directly over the black tank. I can open the toilet and see the bottom of the tank. If your is like this then you can break it up manually.

RandACampin wrote:
What is the water softener suppose to do?

I was thinking the same thing. Wouldn't stool softener be better! LOL :)