Evaporation is a natural form of trap seal loss that occurs when the water in a trap evaporates due to lack of use of the appliance. The rate of evaporation in the UK averages around 2.5mm per week but can vary and is more problematic in hotter climates as the water in the trap will evaporate faster without use of the appliance.

1. Evaporation:
- A natural form of trap seal loss
- Caused by lack of use of the
appliance
- When the trap is not used, the
water in the trap will evaporate
until it disappears completely
- The rate of evaporation can vary
but in the UK averages around
2.5mm per week
- Evaporation is more of a problem
in hotter climates.