Is it a Good Idea to Just Replace the Flush Seal?
Replacing the flush valve flush seal seems a cheaper option. However, in our experience, by the time the flush seal is leaking it is best to consider a replacement valve rather than fiddling about with the time and expense of replacing a small seal. Often, the valve’s other plastic parts have become brittle or distorted with age so the whole unit is defective.
Flush valves are not costly. Once the job is done the new valve will give many years of service. If you are using a plumber for the work (as you should in Australia), then the labour costs will far outweigh the cost of the valve so replacing the seal and then having to have the plumber back soon after is and expensive option.