Over the years, I've had several forum members ask/comment about porta-potties. Most of the comments were negative and some refused to use one.
We use ours regularly and have never had issues, so I thought I would share our procedures and let everyone chime in with different experiences.
First, it is wonderful to have some facility inside and not have to go out when it is cold or rainy or in the middle of the night. So we started using it with some reservations at first.
The most important lesson we learned is to slowly vent the P-P before you use it. If you change elevation you may find an explosion when you flush, and you really don't want to be sitting there when that happens. I slowly vent it before I open the lid. Do it every time and you won't forget the one time that you should have done it. My P-P will vent the storage compartment if you pull the drain handle ~1/2" out before fully opening it. You can hear the whooosh of air venting from the temperature change either during the day (vent pressure out) or over a cool night (letting air in).
After some experimentation, we found a toilet treatment/deodorant that works for us. TST, available from Camping World:
http://www.campingworld.com/shopping/pr ... iquid/2352
You may find other products that work as well. Make sure whatever you use is safe for septic systems.
Water rinse after every use. Ours has an electric flush and after 8 years of use the batteries still do the job. Sometimes you need to wipe up residue that doesn't rinse away cleanly.
The worst part was and is always remembering not to put TP in it. A radical change from civilization, or normal practice for many parts of the world. That said, we use it and a 'trash' bag for paper.
I never let it get full. The dang thing is tooooo heavy when full. I try to dump it at no more than 1/2 full. With the swiveling drain tube on our P-P it has been no problem to dump it. Make sure you hold down the vent valve (button) when you dump to prevent GLUG GLUG GLUG and big splashes. A slow start will make the drain much neater.
A couple of hints. When solids are in the tank, let the P-P sit for awhile (better yet, drive for a few hours to stir it up) so they can liquify. A thick liquid dumps much better than liquid and chunks, cause after the liquid is gone there is nothing to push the chunks out. Rinse the tank thoroughly, 2-3 or more times. Shake it up, turn it upside down, etc. when rinsing to get all surfaces as clean as you can.
Never let the P-P go more than a week without emptying it. After awhile, the treatments are no longer effective and you may get odors that will linger and defy your best attempts to eradicate them. Even if it has only been used once or twice, clean it thoroughly before storage.
Before you start using your P-P it is a good idea to practice emptying it. Fill it as full as you want with plain water, empty. Repeat but vary the use of the vent valve (button) and speed you use to dump and find a method that you are comfortable with.
Then, get out there and go camping and enjoy it!
Mike
Aaaight Mike! Well done on the description... particularly like the one about how the "chunks" won't come out after the fluid is gone! And all jokes aside, 1/2 full is, in fact, too full 'cause they really are heavy.
How'd y'all like that one? 
Sportsmobile (AKA Money Pit)
Linear Mode
