I kept getting a whiff of damp plasterboard every time I went in one of our bedrooms which is unused, but I couldn't figure where it was coming from. The walls are plastered blockwork, not board. Then, Friday, I happened to stick my head in the airing cupboard, and got another whiff. Looking up, the ceiling was clearly damp. The loft hatch is just in front of the airing cupboard, and I knew that the main and central heating header tanks were just above there, so I went up to take a look. The ball valve for the main water tank was leaking - from the threads ...
I shut the water off and unscrewed the union to get a look at the fibre washer, which as it turned out, was not in particularly good condition. Nice easy one, quickly fixed, I thought. However, even after cleaning the seat down and the mating face on the (plastic) ball valve thread, and fitting a new washer, there was still considerable seepage from the threads end of things. I unscrewed the union again and had a close look at the threads, and several were quite badly damaged around the top. It was too late by then to go and get any parts, so I just wrapped a bunch of PTFE tape around it, and screwed back up. I left a bowl and towel under it overnight.
Saturday, I had a close look at the whole thing, and decided that the ball valve was well clagged up with limescale, and wasn't sealing very well either, so I would just start again with a new one, and fit a service valve to the split feed for the two tanks whilst I was at it. Once the old valve was off, I was able to look at it a bit closer, and there is definite damage to about three thread turns for about a quarter the way round each turn. Bear in mind that this is the original ball valve, 20 odd years old, and had never leaked up to this point. So what has caused this ? About the only thing that I could come up with was that the tank is plastic, and the high flow pumped shower that I run probably beats the water inlet, so allows the tank to empty a fair way - certainly you can hear the tank filling for a few minutes after a shower has been finished. This would cause the sides of the tank to flex, and the ball valve with them. The feed pipe was rigid copper, so a considerable strain would be put on the coupling as the tank flexed, and also as the tank reached full, and the float force was exerted on the valve. I reckon that this has caused the damage to the plastic threads and the fibre washer, and initiated the leak - or am I barking up the wrong tree altogether ? This time, I have fitted a metal high pressure ball valve, and 'decoupled' any movement from the rigid feed pipe, by putting a flexi in the line. Does that seem like a good move ? All the plumbing is at least dry now, but I think that the wood tank platform is going to take some time to dry out, unless I hurry it along with a fan heater up there for a couple of hours ...
Arfa