Condensation on Toilet - Cisterns

Summary: Condensation on toilet and toilet cisterns in bathrooms and how to solve condensation issues.

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Diydoctor has devised a method of minimising condensation on toilet cisterns. This is a huge problem for some houses and can lead to bathroom carpets and floorboards actually rotting from the constant drip of water from the water pipes and cisterns in the toilet or bathroom.

If this problem exists in your bathroom or toilet, boxing in the pipes where ever possible can help. Make sure you place insulation inside the boxing also. The hot humid air from the room condenses on the colder water pipes and underside of cistern so any insulation you can use will make things better.

There are fittings available which can add a little hot water to your cistern when the cold water enters after you have flushed. This can be expensive and if it is a loo which is not used often, can be a complete waste. The problem as mentioned above, is that, in any relatively small room, the air gets quite warm. Warm air carries moisture ( see our project on condensation ) which will condense as soon as it hits a cooler surface. The toilet cistern, being full of cold water, is a cold surface.

The answer is of course to ventilate the room to keep everything at a fairly equal temperature but the problem still exists in small bathrooms; therefore we need to make the surface of the cistern warmer and this can be done in a relatively simple way.

Buy a yoga mat, the thin, very dense kind. Strip out the contents of your cistern after turning off the cold water and using a sponge or rags etc, wipe out the cistern until it is completely dry. Then use a hairdryer to warm up the inside. Cut the yoga mat into sections which will fit on the inside of the cistern and stick them in place using the sealant below. The inside of the cistern needs to be completely dry for this to work properly. Make sure none of the mat fouls any of the moving parts of the cistern.

Yoga mat

Yoga mat

Toilet cistern

Toilet cistern

You may need to reset your float valve (see our cisterns and tanks project) because the cistern will now hold a little less water. The yoga mat acts as insulation on the inside of the tank which gives the outside of the tank an opportunity to warm up.

While you have the cistern dismantled it may be an ideal opportunity to insert an isolating valve into the pipe just before it connects to the cistern. This will allow you to turn off the water to the cistern at any point in the future without having to turn the water off to the whole house. It may also be an idea to replace the flushing mechanism with a dual flush to save water. All of these things can be bought below.

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