Water dripping from water tank by pipe in lid

[MsEnforcedDIYer]

I can see the problem but I don't know how to fix it. Where the pipe enters the cold water tank in my loft - this is the small copper pipe that enters through the lid at the side of the tank - I think condensation is forming at the point where the pipe goes through the lid. Even though it is lagged water seems to form between the black plastic lid and the tank by this pipe. The lagging has been absorbing the water here and it has run down the side of the tank - it had been dripping a bit. The chipboard on which the tank sits is also wet in one corner :-(

I tried renewing the pipe insulation with the modern foam tube type and tried pushing this firmly down onto the tank lid to prevent a gap thinking this was where the condensation was forming (when I took off the old lagging the pipe was wet for about 3 inches up from the top of the lid). I also put more lagging round the top bit of the tank and on the lid.

I checked 24 hours later and the new lagging by the tank lid edge is wet so I haven't cured the problem. Though the bucket only has about a teaspoon of water in it and doesn't appear to be dripping now I think it is only a matter of time before it starts again.

The water appears when the cold water in the tank is being topped up. The rest of the time it's ok - well apart from the soggy bit that's not drying in this cold weather.

Any ideas how I can fix this?

 

[MsEnforcedDIYer]

I've found out a bit more ...might be the valve?

I can see the problem but I don't know how to fix it. Where the pipe enters the cold water tank in my loft - this is the small copper pipe that enters through the lid at the side of the tank - I think condensation is forming at the point where the pipe goes through the lid. Even though it is lagged water seems to form between the black plastic lid and the tank by this pipe. The lagging has been absorbing the water here and it has run down the side of the tank - it had been dripping a bit. The chipboard on which the tank sits is also wet in one corner :-(

I tried renewing the pipe insulation with the modern foam tube type and tried pushing this firmly down onto the tank lid to prevent a gap thinking this was where the condensation was forming (when I took off the old lagging the pipe was wet for about 3 inches up from the top of the lid). I also put more lagging round the top bit of the tank and on the lid.

I checked 24 hours later and the new lagging by the tank lid edge is wet so I haven't cured the problem. Though the bucket only has about a teaspoon of water in it and doesn't appear to be dripping now I think it is only a matter of time before it starts again.

The water appears when the cold water in the tank is being topped up. The rest of the time it's ok - well apart from the soggy bit that's not drying in this cold weather.

Any ideas how I can fix this?

I've seen elsewhere someone say that it might be something to do with a broken bidge? Maybe a typo I guess - anyway when the tank was being filled up I felt a very light spray of water coming from somewhere - thought it might have been coming through the roof felt at the time but now think it was from inside the tank and may be the reason for the water coming through the tank lid. It stopped when the water topped refilling. Does this mean I need a new valve?