Toilets have an elaborate plumbing system which carries waste out of the home and often miles away to sewage and reclamation plants. In most cases, as a result of this complicated system, toilets tend to make a range of noises, with some being normal and others occurring due to the breakdown or malfunction of one or more parts. A groaning noise is often a common problem. It comes from a problem with the diaphragm in the bullock (fill-valve). This is the case even if the diaphragm looks like it is okay. It will not require cleaning or repair, but a replacement of the fill-valve diaphragm and an adjustment of the water level in the tank will solve the problem.