Mystery water from tank

[Casperthefriendlyspook]

Looking for a bit of advice.... I went to get clean sheets from the airing cupboard, which also houses the water tank. The sheets and towels were all wet. I've taken everything out of the cupboard, and checked all round the tank, but can't see where it's coming from. No sign of a drip or anything.

I got a new water tank about 3 years ago, as the previous one split, so it shouldn't be a wear and tear fault, I wouldn't have thought. Any suggestions? It is an electric water heater, so old fashioned overnight immersion system. I'm loathe to call out a plumber when I can't see any signs. Any thoughts?

Thanks - off to wash all the affected sheets and towels. :(

You need Pigletjohn on the case with this, but I did wonder if it was condensation?

Pinhole leaks in the pipes - are they copper

Pipes are copper. I've felt them all, and none seem wet, though. I'd be surprised if it were condensation - it's a completely internal cupboard. Also, it's two crates of sheets/towels which are wet, so it seems like quite a lot of water.... Thank you for suggestions!

Google pinhole leaks - I had them in 6 year old pipes

when you say "tank" I expect you mean "cylinder"

Unless it is a white one, I expect there is a cold water tank, either on top of it, or in the loft.

There will be a 15mm copper pipe going to the cold water tank, which holds the cold water supply at mains pressure. Due to the pressure, water is more likely to spray out of this if there is a defect. The spray may be so small that you can't see it, but if you put kitchen roll round all the pipes, valves and connectors, it may show up. Because the incoming main is cold, this pipe will usually be dirtier than the others, and will feel colder.

A leak in a pipe fed from the cold tank, including hot water pipes, will be at lower pressure and is more likely to drip or run out. Again tying kitchen roill round suspect points will identify it.

If the cold water tank is in the loft, it might be dripping through the ceiling.

It is very unusual for copper pipe to pinhole, though steel pipes will rust after about 50 years. More often it is a failed joint which was not made well, so any recent repairs or alterations should be viewed with suspicion.

An old leak on copper pipes will usually have green stain around or under it.

Thanks, PigletJohn. I will check as you suggest when I get home later. It's a cylinder, yes (sorry - not the right word used before). I did put a towel down under it last night, and there's no more water appeared overnight, so I'm a little puzzled that it seems to not be constant. We're in a ground floor flat, so no loft related issues. Ceiling of the cupboard is also dry, so doesn't seem to be coming from upstairs. I will do some more checking tonight!

In our airing cupboard (which may bear no resemblance to yours) we have the hot water cylinder, and also the flue pipe from the boiler in the kitchen below.
This has an inner pipe surrounded by an outer one (like a swiss roll) and the condensate (waste water from condensation from the boiler) collects inside this outer tube and trickles down again. Its a sort of white plastic segmental tube where the one above pops into the secion below...I had dislodged one of these joints by stuffing too much laundry into the airing cupboard and the condesnate fluid had trickled out causing wet washing..does that sound like a possibility?

I'm assuming the laundry you put into the airing cupboard is pretty much dry? You're not using it as a drying cupboard?

Thanks, timetosmile. As it's an electric system, I don't think I have a flue. (Do I?) Certainly no seperate boiler.... and yes - the laundry is dry when I put it in there. Just trying to utilise the little storage we have in our wee flat!

what colour is the cylinder?

I'm home and checked again, and there seems to be no water leaking from anywhere. Towels show no sign of water, and none of the joints seem wet at all, but I have done the kitchen roll thing to see if it will make a difference. I'm really puzzled. :(

The cylinder is lagged/enclosed in that hard polystyrene type stuff. It's green. It has the heating element bit in the front near the bottom. It's round.

Thanks for all the suggestions folks. I'm just really at a loss as to how everything got so wet.... :(

Do you have a cat or a small child who might have crawled in there and weed on them or something?

No pets, and the shelf is way too high for DD to climb up onto. It's not smelly either. Good thoughts tho! :)

Different idea. Is the cylinder raised off the floor so the top of it is near the ceiling, and had you all been away from home for a few days or more before the leak?

looking something like this

the top section is a cold tank with a removable lid.

Thanks - that's exactly what it looks like (just a different colour!)
The cylinder is raised off the floor, near the ceiling, but we haven't been away from home. I think the lid is removable, but I can't get in to see. My arms aren't long enough. DP is back tomorrow, so he could probably get in and look. I really appreciate all the help/ suggestions. :)

the top section is a cold-water storage cistern, topped up from the mains, that supplies low-pressure stored cold water to the bottom of the hot cylinder.

Inside the cistern is a ball cock like you find in an old WC cistern.

If this became stuck or jammed, or had grit or limescale in it, it could continue filling even when the tank was full.

The overflow ought to go out through a white plastic pipe through the wall of the building.

however:
If the oversupply was greater than the pipe could accomodate, perhaps because the pipe was partially blocked by a family of spiders or other detritus, or frozen, then it would spill over the top.

If the overflow pipe was badly fitted or damaged, it could leak at a joint or where it is attached to the tank.

Try pressing the ball float down for several minutes with no tap running, and see if there is leakage. If so, fix the point of leakage and fit a new Part 2 ballcock, preferably a Pegler Prestex. You will also find it is quieter than the old one.

Identify the route of the white pipe and see where it overflows. There may be watermarks around it. They usually go out through the wall and leave unsightly white limescale or green algae stains if they are allowed to overflow repeatedly.

The water may have come from the expansion/vent pipe due to the immersion heater having a faulty stat causing the water in the cylinder to boil and produce steam through the vent pipe which in turn made the clothes wet hence no sign of a leak. worth checking the immersion heater stat.

Thanks to you both for these suggestions. Will look at both, and report back! Much appreciated advice and solutioneering (if that's even a word...)