To replace a plug, force open the round or triangular ring on the chain with a screwdriver. Put on the new plug and squeeze the ring ends into the hole with pliers. At the other end of the chain the last link may be held in a similar way to an eyebolt at the back of the basin.
To prevent a blockage of the outlet in a sink there should be a grid to hold back solids. If hot fat is poured down a sink, follow with enough hot water to wash it away. Periodically run water for several minutes through the outlet to keep it clear.
Use a bell-shaped rubber plunger to clear a blocked basin. Plug the overflow hole near the top of the sink with a cloth. Run a small amount of water into the sink. Put the plunger over the outlet, press it down, then work the handle rapidly up and down. Now lift the plunger away. If the water runs away, the blockage is probably now cleared. Remove the cloth from the overflow hole and allow the water to run for a few minutes. If you do not have a proper plunger, a thick pad of cloth tied to the end of a stick will work just as well.
If the sink is still blocked after using the plunger, look underneath. There may be a U-bend with a drain plug at its bottom. Put a bucket underneath the sink. Steady the U-bend while undoing the plug with a spanner. Make sure you do not lose the washer along with the waste in the bucket Using a piece of wire, poke and loosen any solid matter. Run water in small amounts to wash through anything loosened. If some of the stoppage seems to be further around the bend, poke a piece of flexible curtain wire into it.
There are two other types of traps used under sinks. If the U-bend does not have a drain plug, it will have two nuts so it can be removed completely for cleaning. A bottle trap has a large cylin der instead of a U-bend. The bottom can be taken off like an upside-down screwed lid, but you may need a wrench to loosen it. Most waste will come away when this is unscrewed, but poke along the pipes with a wire as well.
Waste water is usually taken to a drain outside. If the waste flow is still unsatisfactory after clearing below the sink, partial stoppage further along may be the trouble. Flexible curtain wire can be poked into the end of the waste pipe. A better tool is a drain cleaner, which looks like curtain rail but is stouter and has a corkscrew end. Directing water up the pipe with a hose may also help. If this drives solid matter back into the sink or bath, remove it so it does not get washed down again. Run hot water through to wash out trapped fat or grease.
Occasionally lift out the iron or plastic grill from the outside drain. Turn it over and poke or wash out trapped hairs and other matter.