Fix a toilet cistern that fills noisily

Stop a noisy filling cistern by isolating the water, fitting a new quiet-fill valve, and setting the water level correctly.

AB-01Diagnose the noise and check the cistern typeA whistling or humming noise usually means an old ballcock valve is worn out. A constant trickle or banging often means the float is set too high, or a washer has failed. Lift the cistern lid and look inside: modern toilets usually have a plastic float valve on an arm, older ones have a brass ballcock with a rubber washer. Note which type you have before you buy a replacement part.

AB-02Isolate the water and drain the cisternFind the isolation valve, usually a small flat slot on the pipe under the cistern, and turn it a quarter turn with a screwdriver. If there's no isolation valve, turn off the stopcock, usually under the kitchen sink, and check it turns before you start. Flush the toilet to empty the cistern, then sponge out any water left in the bottom.

1 each · Bucket

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1 each · Sponge or cloth

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AB-03Remove the old fill valveUndo the tap connector nut under the cistern that holds the water supply pipe, then the large backnut that holds the valve against the cistern wall. Lift the old valve and float assembly out. Check the rubber washer and tap connector for wear, and replace them if they look flattened or cracked.

1 each · Adjustable spanner

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1 each · Tap connector washer

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AB-04Fit the new quiet-fill valveFit a modern diaphragm-type valve, such as a Fluidmaster or Torbeck, rather than an old brass ballcock. These run much quieter and use less water. Feed the tail through the hole in the cistern, tighten the backnut by hand then a quarter turn with a spanner, and don't overtighten or you risk cracking the cistern. Reconnect the water supply pipe using a new washer in the tap connector nut.

RULES

1 each · Fluidmaster or Torbeck quiet-fill valve

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1 roll · PTFE tape

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KNOW THE RULES

Any replacement fill valve must comply with the UK Water Supply (Water Fittings) Regulations 1999. Buy one marked as WRAS approved.

AB-05Set the water levelMost quiet-fill valves have an adjustable float on a rod, or a screw adjuster on top. Set the water level about 20mm below the top of the overflow pipe, or to the marked line inside the cistern if there is one. Turning the float or screw clockwise usually lowers the level, anticlockwise raises it.

AB-06Turn the water back on and testOpen the isolation valve or stopcock slowly and let the cistern fill. Listen for whistling, watch the float rise, and check the valve shuts off cleanly at the set level. Flush a few times to bulk test it under normal use.

AB-07Check for leaks and tidy upFeel around the tap connector and backnut for damp patches, and dry them off with a cloth. Wipe down the cistern, put the lid back on, and dispose of the old valve. If it still trickles or whistles after this, the overflow pipe may need checking separately.

1 each · Cloth

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