Sink Trap Repairs
DISMANTLING PLASTIC TRAPS
Make sure the container you place under the trap is big enough to hold the contents of the sink or basin before you begin dismantling. (See Problem Solver – Problems with Sink Traps) if there is no room to get a container underneath.
With the trap apart, you should be able to hook out the obstruction with coat-hanger wire. Take the opportunity to clear away any debris around the waste outlet.
Blockages in the waste pipe
If the blockage is further down the waste pipe, removing the trap should make it possible to reach it — either with a sink auger or coat-hanger wire. With upstairs fittings, check the hopper head too: this can easily become blocked with fallen leaves, resulting in the same symptoms as a blocked trap.
If all else fails, you could try using water pressure from a garden hose to shift the blockage. However, to conform with the water byelaws, this must have a double check valve fitted somewhere along its run to guard against back-siphonage. (You may be able to run it from an outside tap containing such a valve.) Pack the mouth of the pipe around the hose to build up pressure in the waste pipe. Few blockages will resist this method.
Most types of plastic sink trap are easily dismantled for clearing, but note which parts go where as you undo them and be sure to save the seals.
If a plastic nut is hard to undo, wrap a piece of rag around it to gain extra purchase, or wear a glove. Only use a wrench if all else fails.
Remove the bath panel to gain access to a bath trap. Empty the bath, and place a tray or old towel under the trap to catch the remaining water.
Bottle traps are the easiest to undo. Most types simply unscrew, but some newer designs have a bayonet fitting which must be pushed up and turned.
Running traps found on shower wastes may be some way from the actual tray. Mark the direction of flow on the side of the trap in pencil before dismantling.
Hopper head blockages sometimes produce the same symptoms as a blocked trap in a fitting upstairs. Hook out the debris and flush with a hose.
A hose used to flush a waste pipe blockage must have a double check valve fitted. Pack around the mouth of the pipe with a wet rag to build up the pressure.