What you can see
Some of the most obvious signs that your drains are blocked are that your shower, basin, sink toilet or bath drain away slowly. If your blockage is particularly bad, then your water may not even drain at all!
If you’re finding only one of your fixtures is having this problem, then your blockage may well be localised to a pipe attached to that fixture. If you’re finding that multiple fixtures are draining poorly, then the blockage may be further down the system in the sewer drain.
If draining of one fixture, such as flushing the toilet or emptying your sink, leads to water rising in another fixture, for example water rising into the floor of the shower, then it’s highly likely you have a blocked drain that will need urgent attention.