How to Replace a Toilet Cistern
CONVERTING TO A LOW LEVEL TOILET CISTERN
Converting from an obsolete high level cistern to a modern low level one may be a necessity if you can’t get the parts you want. For convenience, you could choose a slimline plastic cistern which only requires around 150mm (6″) between the wall and pan. There should also be around 600mm (24″) clearance between the new cistern and the base of the pan.
Most cisterns are sold complete with siphon, lever mechanisms, ballvalve and overflow outlet. In addition you’ll need a new plastic flush pipe and cone fitting, plus materials to re-route the overflow and supply pipes.
If you find later that the seat won’t stay back, you can also buy cranked seat hinge fittings that bring it forward as it is raised.
Doing the conversion
Start by isolating the , then disconnect and remove the old supply pipe and flush pipe; if they are badly corroded, you may have to saw through them. Afterwards, remove any holding the old cistern to the wall, and carefully lift it off its brackets.
The manufacturer’s instructions should specify maximum/minimum heights for fitting the new cistern, so position it first, then trim the new flush pipe to suit. You’ll find it easier to assemble the siphon and other parts before fitting.
Fit the flush pipe with the new cistern in place, then adapt the supply and overflow connections. The new cistern will probably offer a choice of entry positions — side or bottom — so drill out the appropriate blanking holes.
Running in the supply should be a simple matter of rerouting the pipe. To run the overflow, you’ll probably have to make a new hole in the outside wall, then seal around the pipe with mastic.