If you have a problem flushing your toilet, then firstly check inside the tank visually and make sure everything looks okay. If the lever and all its linkage looks okay, then the problem will more than likely be a defective diaphragm washer.Turn off the water supply to the WC tank, there may be a quarter turn valve on the inlet supply pipe. You now need to bail out the water from the tank use a sponge if necessary to draw out every remaining drop of water, otherwise what remains will discharge onto the floor when the siphon is removed. Greenwich Plumbers can replace diaphragm washers. For tanks with a flush pipe, unwind and a large not securing it to the siphon. Next, unwind the big nut securing the siphon to the tank. The siphon can now be lifted from the body of the tank. To complete this action you will need unhook the linkage to the lever arm, if the arm of the float operated valve gets in the way, you may need to remove this also. With the siphon removed you can now see beneath the base and the location of the old perished diaphragm washer. Remove the hook attached to the top of the shaft that pulls the diaphragm, this then allows the diaphragm housing to drop from the base of the siphon. The old washer removed, the replacement can be fitted, these can be bought quite easily. The new washer fitted, everything is replaced in reverse order. All jointing washers should be in good condition, but if they have perished simply wrap some PTFE tape around the joining parts (not around the threads). Turn on the water supply test to make sure it works, also test for any leaks and the job is complete.“