Watts Floodsafe review
A customer had a problem with the fill valve on a Toto toilet.
It turned out that there was a Watts Flood Safe installed for the water supply.
When the toilet refilled, the supply shut itself off.
It seems that the quick filling Toto fill valve (Korky Quietfill) is too quick fo the Watts Floodsafe.
Replacing with a standard supply tube fixed the problem.
It may work with the slower filling Fluidmaster 400 series.
If it senses too much flow, you have to turn off the shutoff, disconect the hose and the put it back together again.
Also, check out this thread,
Watts Floodsafe, Not very.