As DDW posted above, something must have been wrong with the install or the maintenance. I've cruised with Lavacs on 2 different boats for 4 years full time live aboard cruising and have nothing but the highest regard for them. I'm almost disappointed when I go sail on a boat and find I have to use the old fashioned piston type head that likes to clog and never seems to get a good flush and you have to practically study the process in the meantime.

Lavacs are the best, exceeded only by composting heads which I now think are the way to go no pun intended