The small volume of water sitting in a trap disappearing, allowing air from the drain into the room. It can be caused by evaporation in an unused fitting, or by siphonage when a large discharge elsewhere pulls the seal out.
What it means for you
In a rarely used bathroom, running the tap for a few seconds each week is usually all it takes.
Not sure whether this applies to your property? Ask us. There is no call-out charge and the price is fixed before any work starts.
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