The Self-Uninstalling Gas Water Heater

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By Andrew Gabriel

On Wednesday, my trusty Main Medina multipoint gas water heater decided it was time to depart from this world. Age unknown, but I guess at some 20-25 years old, it's filled a fair few baths and handled many showers in its time. Anyway, my Wednesday morning's bath was to be its last. As usual, it did a great job of providing a nice hot bath of water. However, it seems that it had a momentary lapse of concentration, that is, it failed to notice I turned off the bath tap and that the flow of water through it had stopped. Merrily, it continued to pump 33kW of heat into the pint or so of stationary water in its heat exchanger. Well, it didn't stay either stationary or water for longer than a few seconds. What with senility having set in far enough that it had forgotten what its role in life was, and with having found that it could make steam at a rate and at a temperature that Stephenson and Watt would have been truly proud of, it duly embarked on its final mission, to uninstall itself.

Steam production only within the confines of its own pipework was never going to be very satisfying exercise by itself - it would be much more exciting to involve all the household plumbing. There's the little matter of the flow restrictor valve on the water inlet which could limit the rate steam can be pumped out, but since that's only got a plastic centre, suitably hot steam can just melt it out of the way, so that problem is easily overcome. So now let's see how far back up the water main we can blow steam - quite some way it seams, certainly far enough that a very respectable jet can be ejected from any cold tap which someone might happen to turn on. This gets boring after a while - have to find something else to do. Ah yes, get the steam hot enough and under enough pressure, and the solder in all the pipe joins/elbows can be melted and the joints blown apart - now there's a good laugh.

Well, by this stage I'd realised the house plumbing was having a fight with something, and the water heater was starting to let off a bit of a hot smell, so I quickly turned it off, just before any joints had completely separated. This was followed by cold water coming back into the hot pipes, which reset all the solder joints (not how they were before). It then picked up the molten guts of the flow restrictor valve and transferred it back into the water heater, leaving it to solidify in the flow detector pipe constriction, thereby completely blocking the water path through the heater.

Anyway, after a minute or two of surveying the situation and realising I had no further hot water (in fact, not any water out of the hot taps because the heater water path blocked), I decided to go and make the most of the last hot bath I might be getting for a while, which I'd just finished running.

Upon emerging from the bath, a post mortem of the heater and pipework ensued. It was decided against any resuscitation attempts, and death was pronounced.