Toilet Cistern has condensation on it.

11 Feb 2004
Reaction score
United Kingdom
Hi, whats the easiest way to deal with a toilet cistern that drips with condensation. Everything else is dry. But the cistern contains water and you can see where the water is filled too as it has condensation to that point.

Will it need an extractor? or is there an eaiser solution to this?
Sponsored Links
You are on the right track there ... Thats what I would do!
Problem is caused by humid air condensing on the cold surface of the cistern so you must either remove the humid air or stop the surface of the cistern being cold or accept the problem and catch the drips.
Here's some good and bad ideas
Warming the water up - Not an option in my book due to risk of legionella but I think there was mention of a 'device' on here a few months back.
Making a 'cistern cosy' - Many moons ago I went to an house where this old granny knitted such a 'garment' and it worked in that instance!
Boxing the cistern in - Not always an option
Accepting the problem and fit a drip tray - I recently saw what looked like a proprietary drip tray fitted below a cistern. Looked totally naff though.
Dont create airborne moisture - Not having a bath or shower isn't an option unless you are a minger :LOL:
Opening a window - Helps, but what you need is cross ventilation ie air being dragged in through the door and out through an opening so an extractor will help more but only if its in the right place. Fit it next to an open window and it will short circuit the air leaving the moisture in the room to condense on a cold surface.
Hotter air absorbs more moisture so when using a bath or shower turn the heating up a little. I know you will be chucking valuable heat away as well but that cant be helped.

I was taught that the general remedy for all condensation problems is dry heat and ventilation. It is now apparent that in a lot of cases that insulation could be added to that remedy as well.
Condensation is caused by warm moist air meeting a cold surface. There are three remedies. 1 - increase heating (to hold the moisture in the air). 2 - increase the insulation (to prevent the warm air being cooled). 3 - increase the ventilation (to remove the moist air). You may have to pay attention to all three to eliminate the problem. I've heard, but not seen in practice, that your problem might be fixed by sticking closed cell polystyrene insulation sheet inside the cistern, to prevent the incoming water cooling the surface of the cistern. is the toilet in an unheated, poorly insulated room near to a heated, high humidity, room? eg, in an extension with uninsulated ceiling/roof & several external walls off the nice warm kitchen? If so, you can see how all three remedies are relevant
Why don't cistern manufacturers line the system with some sort of insulation foam, job done, no more condensation problems. It could be as easy as spraying on an expandable foam product around the inside during manufacture :confused:
Sponsored Links
What a good idea about the sheeting in the cistern.

Ive discovered that the cold pipes are wet too.

The problem arose because I relocated the bathroom to half in the utility room and half in the old bathroom. The utility room was poorly insulated as this was an extension.

Taking steps to fix it now.

Cavity is partially filled with insulation....will press husband to do rest :LOL:

Will also try the sheeting and will get some pipe insulation too.

We've also lowered the ceiling in the old bathroom half so will also fit extractor to go out above.

Thx for advice
Sounds like progress! For the pipe insulation, you will need to get 'closed cell' type, not 'open cell'. The difference is that if you put it in water, the closed cell type floats (absorbs no water), the open cell type gets waterlogged. Armaflex make a closed cell sort, sold for lagging chilled water pipes in air conditioning. Black, with a smoother surface than normal. the joints have to be taped up. this is to exclude the warm moist air form getting to the cold surface and making the insulation soggy. Much more expensive unfortunately. Not too pretty. Ask at the plumbers merchant for something suitable for chilled water pipes.
You'll need to allow air into the room as well as putting in the extractor, If the extractor was the only opening in a room, the air wouldn't move

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local