Gurgling pipework may be the first sign of a blockage somewhere in your home's plumbing system. Typically, you hear a tell-tale glug or gurgle coming from a sink or shower, even when it is not in use. Often, the sounds seem to be triggered by the flushing of a nearby toilet, or the emptying of a bathtub.
As water drains out of a household waste pipe, air flows into the pipe behind it. When air is slow to follow, a partial vacuum develops, creating suction that produces a gurgling noise. You get the same effect, a sucking, glugging sound, if you pour liquid out of a bottle's neck faster than air can enter. In extreme cases, suction in plumbing can even drain water from another fixture, such as a toilet.
Any plumbing system needs at least one external vent or "stack". This lets air into the drainage pipes. A blocked vent restricts the air supply, causing gurgles. Typically, you find a vent at roof level, directly above a bathroom or kitchen. Look for a vertical pipe that disappears through the roof, or connects to other outside parts of the plumbing. The open mouth of this pipe is often protected by mesh or a grille.
Waste pipes connected to bathroom or kitchen fixtures can become blocked with grease, hair or food particles carried down the plughole. A blockage like this slows the flow of water and air, causing glugs or gurgles. The overflow opening above the plughole in a sink is also prone to clogging.
Waste water leaves your home through drains connected to an underground sewer. If a partial blockage occurs here, the water seeps slowly past it, producing gurgles that echo back up the pipes to emerge from your sink plughole. You might only notice this when a lot of water drains away, for example, from a bath tub or washing machine. You may also notice an unpleasant "drain odour" coming from the plughole.
The waste pipes in your plumbing system converge on their way to the drains. Water flushing through one pipe may draw air past a partial blockage in another, causing it to gurgle. This is why you sometimes hear a noise from one plumbing fixture when another is in use. Sound travels well through the maze of pipes and can emerge at a point quite distant from its source.
Check external roof-line vents for visible obstructions such as birds' nests, moss and leaves. In freezing weather, snow or ice may block the vent. Use a ladder to reach the vent. Clear the blockage with a stiff wire brush. Replace or repair any damaged mesh or grille that covers the vent to prevent further trouble.
Pour drain cleaning fluid down the plughole to unclog pipes. Alternatively, cover the plughole with a sink plunger's rubber cup. Pump the plunger's handle vigorously to shift the blockage. If this fails, insert a long flexible spring called a "plumber's snake" through the plughole. Work the snake down the pipe by twisting its handle to break up obstructions. Flush the unclogged pipe afterwards with copious amounts of water.
You may need professional help to clear blockages in the outside drain or sewer system. Drain clearing firms use a series of long metal rods to probe the drains and break up any material obstructing the underground pipes.