Toilets don't flush silently, but you get used to the noise your toilet generally makes. However, if you hear a loud bang or bangs at the end of the flush, then you will be wondering if something is wrong with your toilet or your plumbing. Why is your toilet making banging noises and what can you do about it?
Single Bangs After a Flush
If your toilet gets to the end of its flush cycle and then makes a short single bang, then your cistern may have a problem. If you stand in your bathroom or toilet and listen at the end of the flush, you should hear the bang coming from the cistern rather than pipes. This problem is sometimes down to a fault in the valve that lets water into the cistern after a flush. If the valve isn't working right, then the water comes in OK, but the valve doesn't cope so well with shutting off the supply. This makes the bang you hear once the cistern refills.
The valve may need to be cleaned out if it is gummed up with stuff. Sometimes, it — or some of its parts — need replacing. If this isn't possible, you may need to replace the whole mechanism inside the cistern and start afresh.
Multiple Bangs After a Flush
If you don't hear a single bang after a flush but a series of short hammering bangs, then you may have a problem with the ballcock in your system. Alternatively, the noises may be coming from one of the pipes that feed water into your toilet. Ballcock mechanisms can make banging noises when their parts wear out over time, so this is more likely to happen if you have an older toilet. If your ballcock is making the noise, then it may need replacement.
Pipes make banging noises for a number of reasons. For example, a loose pipe can bang if it moves against something like a wall when water flow stops. Securing the pipe again should fix this noise. In some cases, pipes bang because they have problems with restrictor or pressure valves. While you can work out if the problem is coming from inside the cistern or from a pipe, you may not have the skills to fix the banging noise. Call your plumber. Tell them about the bangs and where you think they're coming from. Your plumber can take a look at your toilet or its pipes and recommend a fix.