Hg liquid drain unblocker is very safe. As the product is ready for use, there is a much smaller chance of splashes. There is no danger of making the blockages worse, as can be the case with powder or granular products. Hg liquid drain unblocker is thorough & effective. Plastic pipes are of course unaffected. Carefully pour 300 ml of hg liquid drain unblocker in the blocked trap. Wait about 30 minutes for the substance to work & rinse thoroughly with cold water. Unpleasant odours from sink holes can be effectively got rid of with a few drops of hg liquid drain unblocker.. Contains: anionics, sodium hydroxide, water.