jaynews wrote:
I've been unable to solve the low pitched "thunk" noise (vibrating pipes)
that happens when the Fluidmaster 400a shuts off the water after a flush. I
tried reducing the flow at the shutoff valve, but then I got a worse type of
problem of an oscillating bang caused when the toilet shutoff valve closed
beyond a certain point.

I tried shutting off the water altogether and draining the pipes but that
didn't help.

It seems a cost effective solution would be for me to replace the darn
Fluidmaster valve with a Korky Quietfill valve (which does not cause
hammer). Only thing is I hate to having to waste the time replacing the
valve just because of, what, in my opinion, was a bad design choice (if it's
really true that the pipes are being harmed by the abrupt shutoff of the
Fluidmaster.)

According to the Fluidmaster website, they make a "whisper" model that
supposedly mitigates water hammer (albeit with a slower fill). I'm
wondering if a good quick fix could be done by swapping the top part of a
"whisper" model??? Or, is there is any other inexpensive modification I
could make to the Fluidmaster that would accomplish the same thing (WITHOUT
having to drain the tank and remove whole)???

(and, no, I don't think it makes any sense have a "hammer arrestor"
installed is much more expensive than simply replacing the toilet valve)

Doesn't make sense? Maybe you don't want to go to the effort, seeing
as you're hesitating with changing the Fluidmaster, but it still makes
sense.

Just change the valve and get it over with. You're wasting time.

R