Long HW pipe run, how much lagging ?

Hi all
we have a Combi boiler one side of the house (in the utility room). the HW pipe runs across the loft, don through the former boiler cupboard, under floorboards to kitchen and bathroom.
The loft run must be about 6-7 metres.
We have noticed whne temperature starts dipping (as it has lately) the HW temperature does too. In summer it was too hot to touch. Now it's uncomfortably hot, but you can touch it ....
The insulation on the (22mm) pipe in the loft is standard grey foam.
two questions :
1) Am I correct in presuming this temperature drop is caused in the loft ? if so 2) What can I do to upgrade the insulation ? I peeked in the F-in-Ls loft a while ago (new house) and he seems to have circular casing around his pipes, about 10-15 cm in diameter.
Thanks in advance.
Jethro
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It's more likely because the incoming mains cold water is colder than it was in the summer. But if you're worried about the insulation you can buy thicker stuff at B&Q etc which just snaps onto the pipe.
--
Tim Mitchell

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You will probably find the drop in temperature is due to the temperature of your mains water supply dropping seasonally. The combi boiler has limited power and can't heat the water to the same high temperature if it starts off colder. If you already have grey lagging on the pipe, I suspect the losses through it won't be substantial enough to affect the outlet water temperature as much as you are observing. It is still a very good idea to have it, though, as it will help prevent freezing pipes, and will have some effect on efficiency.
Christian.
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