Toilet paper

First time we had our septic tank pumped after 5 years...after he was done he told me I probably didn't need to do any more often than 10 years.  There are only two of us and a large tank.

PSU's paper sure seems logical.  But ..  Our mitigating factors include being empty-nesters, 1000 gal tank (3 br, 2 ba house), and sugar sand as a base soil (to a depth of several feet in most places).  Point being, it's tough to develop a hard & fast rule that works in all cases.  2-3 years is probably "safe" from a regulatory viewpoint but sure could be burdensome in a lot of cases.

We used Scotts single ply TP for quite a while and didn't have any problems.  I really don't think it makes too much difference.  Just make sure you use plenty of water when flushing and keep water in the black tank at all times.  Add several flushes to the tank after dumping everything at the dump station.  It's easiest if you keep some water in your fresh water tank for this purpose and while using the toilet at rest areas, etc.

If you know the black tank is nice and clean, no need to keep any water in it.  If you aren't too sure... a couple or three gallons of water in the tank as you're going down the road will slosh the walls of the tank and prevent bits of toilet paper and other things from drying into a hard crust that can be nearly impossible to remove.  Too much of that and you can have clogs and other potential issues.  I like to fill my black tank with clean water sometimes when I'm home; let it sit for a day or two, drain it and repeat.

TT

It is fairly common to put ice cubes down in the black water tank and ride around to clear stuff of the walls and keep it from building up.