How to Troubleshoot the American Standard Fluidmaster 400

Fluidmaster is a company founded by Adolf Schoepe in 1957 that makes plumbing supply parts. The company is known for creating efficient and reliable toilet fill valves. Fluidmaster fill valves are used in more toilets than all other brands combined and is a leading global supplier of fluid management solutions. Fluidmaster fill valves are commonly used in American Standard toilets, and the Fluidmaster 400 model is the most popular model used in modern plumbing toilet fixtures. There are several ways to troubleshoot Fluidmaster 400 models. Fluidmaster 400 repair parts can be purchased at home improvement and plumbing supply stores.

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Valve Turns On, Off Without Flushing

Inspect the toilet tank flapper for misalignment and wear.

Clean the flapper sealing surface with a rag so it can create a better seal. If cleaning the flapper sealing surface and aligning the flapper to the flush valve doesn't work, replace the flapper.

Inspect the fill valve's black vinyl fill tube to ensure it doesn't extend too far down into the overflow pipe. This creates a siphon in the overflow tube, lowering the the toilet tank's water level and causing the Fluidmaster 400 to turn itself on.

Flush the toilet and check the water level in the tank; if the water level is set too high, water will leak down into the overflow tube and cause the fill valve to turn on. Squeeze the clips on the level adjustment rod and slide the clip down the rod to lower the water level on the fill valve.

Fill Valve Won't Shut Off

Shut off the toilet tank water supply valve under the toilet.

Lift the float arm attached to the valve cap, twist the cap 1/8 turn counterclockwise and lift the cap off.

Cover the opening with a cup to prevent water from spraying. Turn the water on and off several times to flush the Fluidmaster fill valve.

Pull the rubber washer from the underside of the cap and rinse the cap under running water.

Replace the rubber washer under the cap if cleaning fails to remedy the problem.

Fill Valve Won't Turn On

Shut off the toilet water supply valve.

Lift the float arm, twist the cap counterclockwise 1/8 turn and lift off the fill valve cap.

Place the fill valve cap into position on the fill valve, lifting the arm and twisting the cap 1/8 turn clockwise.

Noisy Refill

Turn the valve handle counterclockwise to fully open the toilet shutoff valve; this prevents a restricted water supply.

Tilt the fill valve refill tube angle adapter so the flow of water hits the side wall of the overflow tube rather than going straight down. The refill cycle is much quieter if the refill water hits the side of the tube instead of hitting the water inside the tank.

Shorten the black vinyl refill valve tube and cut the tube the exact length between the fill valve and the refill tube angle adapter. This will prevent noisy refill cycles due to kinks in the refill tubing.


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