Drain odour investigation – under-sink appliance overflow
The customer reported a persistent foul smell originating from the cupboard beneath the kitchen sink. The symptoms suggested that odours from the foul drainage system were escaping into the property, indicating a potential failure of a trap, overflow, or non-return component.
The temporary seal significantly reduced the escape of odours into the cupboard, confirming that the non-return valve issue and open pipe top were the most likely causes. A follow-up with a qualified plumber was recommended to install a permanent, compliant fitting.