The first step to install a Toto replacement fill valve on your toilet is to carefully remove the tank lid. Next, turn off the toilet water using the shut-off valve.
After turning the water off, flush the toilet so that as much water as possible drains from the tank. When the tank is nearly empty, use a sponge or wet vac to remove any water that remains. Disconnect the water supply valve from the fill valve by removing the hose that links them. Locate the lock nut that secures the fill valve to the toilet tank and remove it.
Take out the old fill valve, and discard it. Next, use the lock nut to secure your replacement valve in the old valve's place. Make sure that you follow manufacturer instructions to determine the correct float height after you attach the new valve. Reconnect the fill valve to the water supply valve, and turn the water back on. Finally, check the new setup for leaks.
The manufacturer advises that all replacement parts for Toto toilets be Toto brand to optimize the performance of your toilet. Some models of Toto toilet require a fill valve diaphragm cap in the assembly. To find out which model you own, check the back wall of the toilet tank. The model number is stamped on the porcelain; these numbers are usually three digits long with a collection of letters in front of them.