Absolutely standard problem. Seawater + pee = those crystals. The only solutions are (a) fresh water
toilets; or (b) regular use of descaling agents. Some people use white vinager; others use diluted hydrochloric acid; others use different proprietary liquids.
, as opposed to solution, is best done by being sure everyone on board pumps the toilet enough to get the pee completely out of the pipes. No pee standing in the pipes = no scaling.
A very comprehensive thread on it is here: http://www.ybw.com/forums/showthread.php?t=132681
We use the Jabsco
stuff, which is supposed to lubricate the pumps as well as descale the pipes:
After every cruise
before leaving the boat, we pour the stuff into the toilets and pump it through the system, and let it stand for a few hours. Then we flush it all out with FRESH water
(pour water from buckets into the toilet bowls, while leaving the pump set on "dry"). Then we close the sea cocks and leave the boat.
Has worked ok for us so far (knocking on wood).