Using a plunger If the sink or hand basin is blocked and water refuses to drain out, begin by pouring hot water down the sink.
If that doesn't work, use a plunger or 'plumber's friend' - a large rubber suction cup on a wooden handle.
If you have a double sink, firmly plug the second plughole before plunging the first one, to prevent water spurting up at you.
Cup the plunger tightly over the plughole and plunge it vigorously up and down several times.
If that doesn't work immediately, concentrate on pushing down slowly, making sure the plunger is sealed to the hole and then pulling up quickly.
This tends to loosen the blockage rather than pack it downward.
The same procedure might work for a blocked toilet, but using a cloth mop (the white string tousled type) instead of a plunger.
Push the mop up and down in the bottom of the bowl - a most unpleasant job, but probably necessary! Keep a bucket pretty close by.
Cleaning the S-bend Every sink or basin has an 'S' shape in the pipes directly below the plughole (look in the cupboard below the sink).
It is designed so that water lodges in the first bend, thus preventing unpleasant odours further down the pipes coming up through the plughole.
This 'S' can also trap solid matter (if you've been silly enough to put it down the plughole).
Fortunately, it is quite simple to undo an S-bend, clear the debris, and do it up again.
Scoop the water out of the sink into a bucket, empty the bucket and place it under the S-bend.
Simply turn the plastic threaded flanges as shown in the diagram.
Take care not to lose the O-rings, or the joints will leak when you do them up again.
If there is a tendency for the S-bend to leak, wind some thread tape a few times around the threads before reattaching the flanges.
Drain cleaners It is possible to clear some clogs further down the line by pouring a drain cleaner down the plughole.
However, it is a good idea to get advice from your plumber on what drain cleaner to use, particularly if you have a septic tank system.
Drain cleaners are generally corrosive chemicals or enzymatic substances that break down the clogging material.
Be wary of them as they are hazardous substances and should only be used according to the manufacturer's specifications.
It is also very important never to mix any of these substances or pour different ones down the same drain.
Liquid solutions containing enzymes or bacteria are intended to gradually eat away build-up on the sides of slow drains.
They are safer to use than corrosive chemical cleaners, but they aren't much use on clogged drains.
Liquid solutions containing sodium hypochlorite, sodium hydroxide (lye) or potassium hydroxide are used to dissolve grease and hair clogs.
Solid granules or crystals of sodium or potassium hydroxide also dissolve grease and hair.
All products should be used with caution and following all directions.
Maintaining clear drains For a non-toxic regular drain cleaner, pour ¼ cup bicarbonate of soda down the drain.
Follow it with ½ cup vinegar and plug the drain until it stops fizzing.
Rinse the drain thoroughly with hot water.
Washing soda is also a valuable non-toxic method of maintaining free drains.
Pour a tablespoon of crystals down the plughole.
Leave for a few minutes than follow them with boiling water.