- a small amount of water contained in the trap of a drain to prevent the passage of foul smells
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Examples from the Web for water seal
Between the soil-pipe and the fixtures a trap must be provided with a water-seal of about an inch.Rural Hygiene
Henry N. Ogden
The best arrangement in all respects, especially between the generator and the holder, is a water-seal.
There are two automatic devices which may be employed for the purposes in view, the non-return valve and the water-seal.
It bubbles through the water in the washer, which therefore also serves as a water-seal, and passes thence to the gasholder.
The flanges of the cover were sufficiently long to dip into a water-seal surrounding the tank.The Preparation of Plantation Rubber