Geoff Wells, bathroom planning expert for Dolphin Bathrooms, comments:

“All air contains moisture to some degree and warm air holds more moisture than cold. Condensation occurs when moist air comes into contact with other air or a surface that has a cooler temperature. The problem here is that the warm air created when the shower has been in use is hitting the chinaware of the cistern which contains cold water, resulting in heavy condensation.

“The best way to overcome condensation is to ventilate the room effectively. After showering, close the bathroom door and open the windows as much as possible in order to allow the moisture in the air to escape. Alternatively, consider installing a good extractor fan, such as those with a special air-moisture switch that will come on automatically when moisture reaches a certain level.

“If you were considering making over your bathroom, I would recommend installing a back-to-wall WC with a plastic cistern enclosed inside fitted furniture. This would give the cistern an air pocket between the furniture, thus eliminating the condensation issue altogether."