how can i fix my toilet cistern?

it sounds like you need to change the valve on the float operated valve inside your toilet cistern. turn the water off at the service valve on the inlet pipe, and strip down the float valve. there are two types of conical shaped valves here used depending on if toilet is directly fed by mains pressure or the cold water storage cistern in the attic,which means you only have water pressure depending on the head,i.e distance tank is above toilet. red one for high pressure and white one for low pressure. low pressure one has larger diameter hole to let more water in so change it to this one and see what happens.

robert
December 2007