Exessive Condensation Around Loft Tanks

22 May 2008
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United Kingdom
Discovered damp patches on ceiling today and found that there was a huge amount of condensation around one of the two 25 gallon loft tanks (the one with the mains feed) which had gradually collected and wicked through the loft insulation. We had the loft re-insulated about 12 months ago and the company left the original tank jackets on and added another over the top with a new lid. It seems as though the condensation is collecting on the tank lid and then running between the two jackets - rather than dripping back into the tank - these are the all in one plastic/glasswool jackets. I guess this has been happening since the additional insulation was added.

My question is - should there only be one jacket? We've never had a freeze in 28 years. I've also removed insulation from under the tanks - I questioned this at the time but they (Miller Pattison) said it was normal to insulate underneath now with the extra tank insulation provided. Also does anyone know if the fitted lids for circular tanks allow any condensate to drip back into the tank although I doubt I'd get one to fit exactly considering the age of the tanks.( Loft is vented at both gable ends and eaves are clear of insulation.

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Are you sure it's condensation and not a leak?

I've checked and can't see any leak from any of the outlets or connection to the other tank. I've drained down and the tank seems sound, I can't see any cracks or anything - are these poly tanks prone to leaking? If it is it would be really slow as the inlet valve doesn't drip and when I removed the jacket it was really wet between the layers. The vent pipe is well positioned within the tank and wouldn't go over so I stll think its condensation. I'll leave the jacket off for afew days and let things dry out and see what happens.

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is the water in the tanks cold ?

Yes it is. Both tanks have a lot of condensation between the jackets but the one with the mains feed in had much more. Never had this until they were double lagged last November. Short of lifting the tanks to see if there's a leak from the bottom I don't know what else to do. I've removed the jackets at the moment to see if the chipboard platform that they stand on dries out. I guess if it does then this is the problem, I can't see any evidence of leaks from any pipework joints; the CH FE tank is also on the same platform and I've checked that for over pumping & leaks but nothing.

Thanks for your help.

check the bidge has not been broken - if it has water spays all over the place when refilling but stops when valve shuts off

check the bidge has not been broken - if it has water spays all over the place when refilling but stops when valve shuts off

Thanks Mick, the valve is the older type with a bottom outlet. However this problem may have occurred recently and not over time as I thought - we have been away for a few days and I turned the water off as usual. I'm told that what can happen is the fibre washer in the tap connector to the valve can dry out and then leak once the water is turned back on until it expands again (it's 28 years old). I wouldn't have noticed this as this fitting is (was) all covered by the tank lagging. I have someone coming to look next week, and check/change tank if necessary - thanks to everyone for their advice. Much appreciated.

check the bidge has not been broken - if it has water spays all over the place when refilling but stops when valve shuts off

Can you tell me what a bidge is ? What is it part of? I think this may be the problem I have with water leaking out of my water tank by the pipe that goes into the top of the tank. I felt a light spray of water when investigating the leak as the tank was being filled up. I thought it was coming from the roof but now I think it wasn't. Up til now I thought it was condensation from the 'in' pipe but not I'm not so sure. Got some nice soggy tank insulation near the tank lid.

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