The replacement of a toilet flush valve may be needed when replacing the flapper and other attempts to repair a running seat havent worked. If a toilet flapper doesn’t seem to seal it could be that a toilet flush valve replacement may be the answer. You could ask a Plumber to do the job for you if you are not confident. Here is a basic guide: The first thing to do is, isolate the water supply as the toilet cistern needs to be taken off to carry out the task. When the water is off, flush the toilet to drain the cylinder and then wipe out the remaining water in the cistern. Undo the water supply coupling nut from underneath the tank. Undo the bolts that hold the toilet cistern to the bowl. Use penetrating oil if the bolts are too tight. Unhook the chain from the handle. Place the cistern on an old towel. Take off the spud washer (which is large rubber) and its nut from the bottom of the flush valve using a wrench. London Plumbers are trained professionals. Remove the old flush valve and fit the new flush valve in the valve hole and check the top of the overflow pipe is at least 1″ under the cistern high level mark and the hole where the handle fits. Place the flush valve below the handle lever arm, fixing it to the cistern from underneath with the spud
nut. Hand-tighten the nut, then slightly more with a spud wrench or channel type pliers. Be careful not to crack the cistern when tightening the fittings. Put the new spud washer over the spud nut, small side down. Put the cistern down face up and place the correct washers onto the tank bolts and insert it into the holes from inside the cistern. Put the brass washers and hexagonal nuts onto the bolts from below and tighten them slightly more hand tight. Now place the tank over the bowl and sit it down so the washer will sit over the water inlet in the bowl and the cistern bolts fit through the holes in the bowl flange. Fix the cistern and bowl together. Always test and check for any leaking.