I have a Toto toilet that came with our apartment, so the model number/year is unknown - or at least, the model number is nowhere to be seen. I've been having problems with the toilet squealing when it is NOT being flushed or the tank being filled - it will, when sitting there idly, start to whine and squeal extremely loudly. This is fixed by turning off the water to the toilet. However, this is a main bathroom and it's getting out of hand.

I have been told that it's either the fill valve or the flapper, or both. The fill valve is a Fluidmaster 400A, and the flapper doesn't seem to have a model number on it. I've contacted Toto customer service, but I can't locate the model number, so they're not much help. At this point, I figure it would be easier just to buy universal parts and replace something myself.

So far, I have removed the top of the fill valve and cleaned it, ran water through the fill valve while the top was removed to rinse out any grit, put silicone grease on the seal, and reinserted it. This seems to help - but eventually the squealing will return, usually within 24 hours. I haven't done anything with the flapper - the toilet isn't leaking water into the bowl from the tank, and I have tested this with dye.

I figure that I should probably just go get a new fill valve, but the one currently installed doesn't look that old. If I go buy a new fill valve, what can I do to prevent this from happening? What about replacing the flapper?

If the flapper was leaking, the dye test should have shown that. When the toilet tank fills up after a flush, note the water level in the tank. When the noise starts, check and see if the water level has dropped or still the same. If still the same, try turning on the sink faucet for a moment and see if the noise stops. If the level dropped, there's a leak, usually the flapper.

with a 400A you don't always have to change the entire valve. the rubber washer that you said you put silicone grease on is replaceable.

I don't remember any model of Toto using a Fluidmaster 400A, from the factory. I believe there was a reason for that. Have you consider going OEM, instead?

Best Wishes

IF the water is not leaking into the toilet and the fill valve shuts off, there is no reason why it would "turn on" and make the noise, so change the flapper first. Toto buys the same generic flapper you will get from a good store.

I seem to remember that Hunter was making the internals for ToTo in the beginning..... Has anything changed?

Best Wishes

Steve, you suggested turning on the sink faucet when the squealing is occurring to see if it stops. It does (I have the same problem). What does this mean?

Thermal expansion from the water heater will increase the pressure in the entire house in a closed system. Running some cold water will help to bleed off the excess pressure. If that helps, you need a thermal expansion tank installed, and possibly a pressure reducing valve as well.