When a toilet has a problem, it usually gives you a clear sign, and knowing the signs can save you money. If the tank refills by itself when nobody's touched it, water is leaking past the flapper and adding to every bill. A toilet that keeps running after a flush usually has a fill valve that has stopped shutting off. If the toilet rocks at the base, the mounting has often loosened, and the wax seal underneath may fail next, which can turn a toilet problem into a floor problem. Water at the base means the floor is already involved.
Most of those are straightforward repairs. The parts inside a toilet can be replaced one at a time, and a toilet in good shape can keep working with new parts now and then. Replacement makes sense when the porcelain is cracked, when repair costs keep stacking up on an older toilet, or when you simply want something better. Modern units use less water, and a bidet is worth asking about when a toilet's being replaced anyway.
If the toilet keeps backing up, the problem is usually in the drain line rather than the toilet itself, and that's its own service with its own page. Everything else on the toilet, whether it runs, rocks, leaks or needs replacing, is performed by or under a licensed contractor, explained in plain English and decided by you. A toilet that isn't set and sealed carefully can leak over time and leave a stain on the ceiling below, so it's worth doing properly.
