Dealing with a blocked drainage system is one of those tasks most of us do not look forward to, but it is as necessary as it is potentially grotty, so how is it done?
Using a Plunger
All drainage systems will become blocked, so the first task is to locate the blockage itself only once this is done can the correct course of action can be taken. A plunger functions by using changes in air pressure to dislodge the blockage. The device is most effective when there is water backed up from the pipe to the plug hole.
This is because water does not compress and so transmits the applied force much more effectively than air, which as a mixture of gases does compress. Pressing the plunger into the drain forces air in and when the plunger is pulled out a vacuum is created and it is this process that loosens, dislodges or breaks up whatever is blocking the drain.
If the plunger does not work then before dismantling the system try using a steel or metal snake that can be pushed into the blockage.
Checking the Waste Trap
If the plunger (or snake) proves to be ineffective, the next task is to check the waste trap. It is located under the plughole and provides air and water tight seal between the drainage system and the external environment.
First, make sure that the sink is as empty as possible the more water you can remove, the less is going to spill when you open the pipe. Make sure there is a wide receptacle to collect any spillage and then take the waste trap and dismantle it and remove any waste material under a stream of running water. At this juncture it would be advised to make any additional repairs, cleaning or maintenance to the trap. Then refit it and run boiling water an appropriate cleaning solution through the entire system to remove any residual material. This technique also applies to blocked U-bends and U bend traps.
These are highly corrosive substances (normally concentrated alkalis) which are poured into the drainage system and must be used following the manufacturers instructions. If these say wear rubber gloves wear them, spillage will hurt!
The concoction functions by literally breaking the blockage down by chemical means and often requires a minimum period of time to work and it may also be necessary to use the cleaner in a well-ventilated setting. In addition, different cleaners are designed to work inside drainage systems made of different materials, we are seeking to dislodge the blockage not dissolve the pipes, so if in doubt check before use.
Finally, once the water is flowing properly to keep the pipes clear for longer a little preventative maintenance is in order. Strainers in the plug hole will mean that physical debris does not begin to accumulate.
A monthly infusion of boiling water will help emulsify any fats and grease thus curtailing their build up. This can be combined with a dose of vinegar followed by a dose of bicarbonate of soda, both of which can be flushed away with a further liberal dousing in boiling water.