I have two gray
water tanks originally built with flapper-type float valves to actuate the Whale Gulper 220 pumps which evacuate them.
I have always hated them -- especially the aft one which takes kitchen gray
water so stinks like hell when I have to open it up.
One of the float valves failed in the stinky one last summer during my summer
cruise. I replaced it with the only new one I could get my hands on (no spare) an el-cheapo from a
chandlery in Tallinn. It failed in its own turn just 8 months later. Still no spare on board, so yet another el cheapo from the local
chandlery 
. I don't expect it to last long.
Then last week the float valve in the forward gray water tank failed. This time I had time to look for a better device to replace it with, and allowed myself to get talked into a Johnson Ultima solid state one.
It was not a drop in fit but I managed to make it
work and I'm reasonably pleased with how it is mounted. And it works like a champ so far.
NOW I want to lay in a spare for the aft one, for that inevitable day when the next failure occurs.
I use the Ultimate Junior float valves for my
bilge pumps, but something like this would be overkill for gray water
tanks and probably wouldn't fit.
So what do people think about the Johnson solid state ones? Should I be
buying one of those to keep in spares for the aft tank?
The old flapper valves lasted a hella long time -- they were original to the
boat, one failed at 17 years old and the other at 18 years, and that is not light usage. They were "Rule A Matic" ones, which I believe contained mecury, the absence of which due to regulation is no doubt why the modern ones are such crap.
So -- solid state? What experience do people have?