Replace a toilet flush valve

Replace a leaking or noisy toilet flush valve safely, working from isolating the water to testing the finished flush.

RV-01Identify your valve type and buy the right kitTake the cistern lid off and look inside. An older syphon lifts water using a plastic diaphragm and single flush handle; a newer drop valve has a rubber flap and usually a dual-flush button. Take a photo of the cistern make and model to the shop, since syphon kits and drop-valve kits are not interchangeable. Gather an adjustable spanner, pliers, a bucket, and old towels before you start.

1 each · Flush valve or syphon replacement kit

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1 roll · PTFE tape

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RV-02Isolate the water supply and drain the cisternTurn off the isolation valve on the pipe feeding the cistern, or the stopcock if there isn't one. Flush the toilet to empty most of the water, then hold the handle or button down to drain as much as possible. Soak up what's left inside the cistern with an old towel or sponge.

RV-03Disconnect the water supply pipeUndo the nut on the tap connector where the pipe joins the cistern, using an adjustable spanner. Keep a bowl or towel underneath, as some water will still drip out. Move the pipe clear so it doesn't get in the way when you lift the cistern off.

RV-04Remove the cistern from the panOn a close-coupled toilet, undo the two fixing bolts underneath the cistern using a screwdriver while holding the nut steady underneath, inside the pan. Lift the cistern straight up and off. On a low-level toilet, disconnect the flush pipe from the base of the cistern first. Rest the cistern upside down on a towel on a flat surface.

RV-05Remove the old flush valveUndo the large plastic retaining nut on the underside of the cistern, holding the valve steady from inside so it doesn't spin. Lift the whole valve assembly out, along with its rubber sealing washer. Note how the handle or button links to the valve so you can fit the new one the same way round.

RV-06Fit the new flush valveFit the new sealing washer onto the new valve, then push the valve through the hole in the base of the cistern. Hand-tighten the retaining nut underneath, then snug it up with a spanner - do not overtighten, as this can crack the plastic housing. Reconnect the flush handle or button linkage to the new valve's lever or stem.

RV-07Refit the cistern onto the panLower the cistern back onto the pan, lining up the fixing bolt holes. Fit new sealing washers on the bolts if supplied, then tighten by hand until snug, followed by a gentle quarter turn with a screwdriver - overtightening can crack the ceramic. Reconnect the flush pipe if you disconnected it on a low-level toilet.

1 each · Cistern fixing bolt and washer set

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RV-08Reconnect the water and check for leaksReconnect the tap connector to the supply pipe, wrapping the thread with PTFE tape if it's a compression fitting. Turn the isolation valve or stopcock back on slowly. Once the cistern fills, check underneath and around every joint with a dry hand or tissue for drips.

RV-09Test the flush and tidy upFlush the toilet several times, checking the valve seals fully each time and the cistern refills without running on. Adjust the float or fill valve if the water level looks too high or low. Wipe down the cistern and floor, then dispose of the old valve and packaging.

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