Post
by marrtin »
Thu Nov 15, 2007 9:47 pm
As you are aware, a normal trap works by creating a seal using water to prevent odours from entering the room. In certain conditions this water can under vacuum be drawn out of the trap leaving it empty, and consequently leave a free passage for foul air.
To prevent this, anti siphon or anti vac traps have a one way valve fitted that allows air to enter the trap on the drain side and remove the vacuum which ensures the water seal is not broken. It is not usual to fit these unless this symptom is experienced.
You can get traps that have two connections - one for a washing machine, the other for a dishwasher say. In the past I have tested by draining both appliances together, and the sink still empties at speed!!
I always use this type of installation if the washer or dishwasher is next to the sink.