I already mentioned pools of water and houses and the question not being if it will happen, but when. It seems a bit soon to get another one, and a little inconvenient that it was on a Sunday when I had to work.
When I was making breakfast I saw the small puddle and the drips coming from the ceiling in the utility room. The utility room is directly under the bathroom, so that's where any water is going to end up. Although it doesn't have much respect for a house free of fungi, water does at least obey the laws of gravity.
The first reaction was to call the plumber. Actually the first reaction was to get a bucket for the drips and a cloth for the puddle as it still hadn't got very far. Also, since it was dripping quite slowly, I thought we should let the plumber finish his breakfast.
I finished my work early enough that the plumber was still working, searching for the source of the leak. When I spoke to him on the phone, he hadn't found it, and was about to give up and go home. He said the water was not coming from the bath or any leaks in pipes there, but from the wall between the bath and the boiler.
Thinking about the mystery on my way home, like a Poirot of plumbing, it increasingly seemed that the ventilation system was the problem. In the process of exchanging heat, the ventilation system takes a lot of water out of the air, which must find its way through a drain out of the house. This seemed the most likely source of the water.
The night before had been the first below freezing, and I wondered whether the outside drain from the ventilation system had frozen over, stopping the water from escaping. Of course the temperature had only just dipped below freezing, so it wasn't cold enough for pipes to freeze, and there had not been enough time for a dam of water to build up and get through the ceiling.
When I got home, the first thing I did was look at the drain as it leaves the house on the East side. There was no ice there. In fact the drain pipe itself was dry.
The plumber showed my the pipes above the utility room when I got into the house, and the one that water was dripping down the outside of. We went upstairs to the boiler, which was installed by different tradesmen and was not really his responsibility. There were pipes coming in from the external heat exchange units for the boiler, and the air conditioner that we don't use. There were just two pipes for each: a supply and return for the coolant. No drains.
I then suggested the room upstairs, which he had had nothing to do with, and was unaware of. Above the bath is the machine room with the solar power conditioners and the ventilation system.
And there was the smoking gun. Or at least the dripping pipe, and a pool of water underneath the ventilation system.
The pipe coming out of the ventilation system had come out of the drain in the floor. It had not been fixed in there, but was just pushed in, the ventilation "experts" no doubt hoping for the best. I go into that room about once a month, and it could well have been knocked out when I was vacuuming the floor last time I was in there a month before. Water had been slowly dripping onto the floor, gradually increasing in flow as the outside temperature dropped. As it found its way down past the bath, following the pipe, it would gradually have evaporated back into the house. For the last couple of nights, as the temperature dropped to around zero and the amount of moisture coming out of the air in the house increased accordingly, more or the moisture got to the puddle above the ceiling of the utility room, and in the morning it finally got through the drywall. In fact the dry wall was now a wet ceiling.
It's a good thing we'd just used drywall for this room rather than a plastered and painted ceiling. A screw driver is enough to take a panel off, and it can easily be replaced without needing to call in a procession of tradesmen. The drywall panel is now propped against the wall to let the ceiling dry out, and I can put it back again in a couple of days without having to call the plumber out again.
