Fixing a toilet fill valve (sometimes known generically as a ballcock) is relatively easy to repair if you happen to have a Fluidmaster brand valve. Often, repairing a fill valve is done by simply replacing the entire fill valve, but Fluidmaster fill valves can be repaired by just replacing a seal inside the unit. If your Fluidmaster fill valve is not shutting off all the way or not filling quickly like it did when it was new, then replacing or cleaning the fill valve seal will most likely fix the problem.
Replacement seals for Fluidmaster fill valves are widely available at home centers and hardware stores. You should have no trouble finding one. And while you're at it, pick up an extra to have on hand the next time you have a problem. They are very inexpensive.
How to Replace a Fluidmaster Fill Valve Seal
Before you get started, locate the shutoff valve that controls the water supply to the toilet. The valve is usually located on the wall below the toilet tank and has a small handle. The valve will be connected to a water supply tube leading to the bottom of the toilet tank.
- Shut off the water to the toilet by turning the handle on the shutoff valve clockwise until it stops.
- Flush the toilet to remove most of the water in the tank.
- Loosen the plastic cap on the top of the fill valve: Wrap one hand around the fill valve shaft, then slide it up to push the float cup (the large plastic cylinder that slides on the valve shaft) up towards the top of the fill valve, and grasp the shaft firmly. Use your other hand to turn the cap on top of the fill valve counterclockwise 1/8 of a turn. It may help to push down on the cap while turning.
- Lift the cap from the top of the valve and set it aside. The valve seal is inside the cap.
- Place a mug or drinking cup upside down over the top of the valve and hold it in place with one hand.
- Use your other hand to carefully open the shutoff valve by turning it counterclockwise. Water will flow out of the fill valve, into the cup, and then down into the toilet tank. This flushes any debris from the valve. Close the shutoff valve by turning clockwise until it stops.
- Remove the old fill valve seal from the valve cap.
- Install the new valve seal, fitting the nipple on the seal over the stainless steel needle in the cap so the nipple goes up into the cap; this should match the orientation of old seal.
- Reinstall the fill valve cap by fitting it onto the valve as before and turning 1/8 turn clockwise to lock the cap in place.
- Open the shutoff valve slowly turning counterclockwise until the handle stops.
To finish the job, let the valve refill the toilet tank, then flush the toilet and check the operation of the fill valve. Also check for any leaks at the shutoff valve.