I have two Lavac's - one manual one electric. I couldn't be happier
with them. No valves. No clogs (at least that I've ever witnessed).
Very quiet. Easy to clean. Uses little flush water so my holding tank
lasts longer. You do have to post useful instructions to guests (and
explain it to young children) but most seem to find these less
confusing than the instructions for a traditional head. Defender
reliably stocks parts.

Carl