In Hong Kong you may be able to purchase one of the following tools from local hardware store to try first:
For sinks/basins unscrew the 'U' bend below the sink. You will want a couple of buckets handy depending on how much water is collected in the sink. 90% of the time the blockage will be in this part of the pipe.
First of all we are biased and do not like the use of chemicals because of their effect on the environment.
Also the variation in the chemicals Hong Kong offers leads to unpredicatable results. They range from too weak (basically does nothing) to absurdly strong (potentially strong enough to eat through PVC pipe if left for too long).
Unfortunately for these reasons if you have used chemicals and had no success and decide to call us, we are going to have to take extreme care when attending to your drain. In addition we won’t insert our camera or jetter hose in the drain until the chemicals have drained away so as to avoid damage to our equipment.
For those of you who still decide to use chemicals please take the following safety precautions:
Prior to using chemicals make sure you remove as much water from the fixture as possible, whether that be the sink, shower or toilet. This is because adding 1 litre of drain cleaner to 10 litres of stagnant water will dilute it so much that it isn’t going to do much unless it’s extremely strong. Results from using chemical can take hours or even overnight.