If it is not very full run hot water into it with the drain open.  If full you can suspend something like this in your black tank through the commode MAKING SURE it is not touching any pipes.  It will take awhile, but may work.  Something like this which is a sealed unit that can be completely submersed.  Third idea is drive south.....   DH asked if you are sure the black tank is frozen or is it frozen in the piping that drains it?

That is an incredible idea, Talensnana!

...suspend it in the poo poo water through the toilet hole!

Then 'afterward' use it to boil some water in a cup, for a nice warm cup of tea!

(Only kidding about the last part! )

Yes, I've had the same freezing problem just a couple of weeks ago.

...luckily the weather got warmer, which opened up the flood gates for the deluge of 'unmentionables' to come flying out!

Many years ago, I lived 'stationary' in a motorhome for 7 years.

I remember now, not to have any droops in the sewer hose, so the sewer water cannot collect 'in-mass' in the hose.

AND, despite what everybody else says, always leave the sewer spigots 'wide open' when attached to an underground sewer hole.

Here is my reasoning behind this:

It allows warmish air from the fermenting sewer under the ground to flow up through the tank and pipes, up and out through the pipe vents on the roof, thereby preventing anything from freezing.

My condolences to azreark. - It's a horrible thing when it happens.

...not to mention the 'trauma inflicted' while sitting in a cold motorhome, realizing the sewer piping could very well be cracked from the freezing.

The only unfortunate thing about that water heater is that there's no way to suspend it in the wash/shower holding tank.

I'd like to see some solutions for that.

Terry and Jo wrote:

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Millie,

With all due respect, one needs to leave the black tank valve closed when not actually dumping.  Otherwise, one gets a pile of stuff in the tank directly under the toilet.  That stuff has to be in water in order for it to liquify and be able to be flushed out.

Terry

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Terry:

Extremely good advice.  Not following the procedure of “lots of water in the black tank before dumping” can lead to the dreaded “pyramid of doom” as you more eloquently described the resulting situation of leaving the black value open all the time.

This is a very big deal.  Don’t leave the black tank value open all the time.  The results will not be pleasant at the least and expensive to fix at the worst.

Barbaraok wrote:

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If you are a newbie reading this thread, please take Mike's statement to heart. NEVER leave the black tank open, ever. In freezing weather, attach hose to dump, rinse hose, then put it away until your tank is at least 2/3 full before dumping again. In addition to the dreaded pyramid, leaving drains open can allow fecal flies to migrate into your tanks. Even in warm weather, we always keep both tank valves closed.

Barb

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Barb:

Some will say this is overdoing it but we also leave even the gray tank value closed and then dump it when it’s almost full.  IMO that will better flush out the particles and maybe even some of the “grease” that may build up on the bottom if you leave the value open all the time.

You’re the chemist, but I think you will agree this is the best way to keep your tanks in good order is pretty easy to do.  Lots of water in one big dump does the best flushing job, IMO.

This side of a broke frame or delamination, I can’t think of anything with an RV that is worse to deal with than a holding tank issue.

Bill

Well, if ya'll have a hankerin' to be thinkin' 'bout your sewer 24 hours a day, far be it for me to try and dissuade ya's from it!