There are some cleaning agents for sale that can be used to try and clear a blockage in pipe. However, these can be very dangerous to the health of anyone using them if not used correctly. Waste pipework has to deal with lots of things from food to human waste to food waste so it is no wonder that these cleaning agents are sold to try and unblock pipework. There is a tried and tested way to deal with a block and that is to use a very simple device called a Plunger. These can vary but the principle does not change, that is, to try and force high pressure or vacuum into the system to try and loosen up the blockage. With some water just covering the plunger base, pump back and forth a few times to create the vacuum. Do this several times if it does not do the trick. Bounds Green Plumbers can plunge a sink. Pipework blocks that are in hard to get to to places and cannot be dealt with by normal means for example deep in a pipework system some distance away can be dealt with by something called a drain rod. As its name implies it is a long narrow rod that can be up to 6metres in length and made up of threaded sections that screw together to form one long piece (if needed). On one end of the rod is a corkscrew piece should tangle itself with the mass, so it can be dragged out. The traps that are fitted below sinks can also become blocked, so make sure that you have a bowl situated under the trap before you open it. When this is done you can undo the trap and hopefully clear the block, generally by hand, and catch any water etc. in the bowl. Once it is cleared, re-assemble and replace. Check for leaks and also see if the water is flowing again. A Bounds Green Plumber can carry out this task.