Incoming water pipe and condensation

Normal on the winter when the incoming water temperature is lower than internal dew point.

Closed cell insulation is what is needed. This will insulate without absorbing water. Most pipe insulation should be such if WRC approved.

In message , Steven Campbell writes

If there's moisture in the surrounding air (which there will be), there will certainly be condensation on the pipe.

Insulation should certainly help, as it would minimise the amount of cold pipe directly exposed to the moist air.

However, instead of the 'foam rubber' type of insulation, consider wrapping the pipe in some material which easily absorbs water. If the pipe still becomes wet, the material will also become damp, and this will allow evaporation to occur more readily.

Under my kitchen sink, many years ago, I 'temporarily' wrapped some kitchen tissue around the incoming water pipe. [Occasionally, the tissue gets renewed.] Maybe something like an old cotton vest would be more permanent. Or I wonder if the 'old-fashioned coarse hairy stuff' which they used to use word be suitable?

Thanks guys. I'll put something on it. Interestingly enough, the pipe that comes from under the floor already has that "hairy stuff" and although it does seem damp its certainly not dripping like the horizontal run of pipe above it.

In article , Ian Jackson writes

Couldn't disagree more I'm afraid, wet insulation is no insulation at all so condensation will continue, all you are doing is storing moisture that may evaporate if the conditions change or will stagnate and smell if it doesn't.

Closed cell insulation will stop moist air reaching cold surfaces and will reduce condensation. Also, being closed cell, if any cold surfaces remain exposed and limited condensation does occur, the insulation will remain effective in the presence of the reduced moisture.

Just checked and the brand name Climaflex (conventional extruded grey pipe insulation) is closed cell and suitable.

In message , fred writes

Well, it's just a suggestion. My 'kitchen tissue lagging' usually seems quite dry. But I think if I was going to do things properly, I too would probably try the foam first.

Aren't mothers-in-law a protected minority nowadays?

and if the pipework and/or fittings are iron, cause them to slowly rust through from the outside.

Agreed.

Armaflex is another manufacturer, or any pipe insulation intended for chilled pipework on aircon systems. Might be difficult buying a short length though.

You could simply try a piece of the dark grey foam insulation sold for heating pipes. Although not explicitly sold as closed cell, some of it looks like it may be. As you are fitting to an existing pipe, you will need to split it, and this needs to be re-sealed air-tight afterwards with something like wide insulating tape binding and sealing the outside of the insulation (and that applies to any closed-cell insulation you use and have to split too).