Hot water has to reach fifty degrees at the outlet within a minute, measured with a probe, and written in a logbook, because below that is where legionella lives. One tap in this school reaches forty three and stops, and it is fed by a pipe that is not connected to anything.
I am a water hygiene technician and I look after about sixty buildings, most of them schools.
What the monthly job actually is.
You take a sentinel outlet, which is the nearest and the furthest tap on each circuit, and you run it and put a probe on the water. Hot has to be at fifty degrees within one minute. Cold has to be at or below twenty within two. You write the figure, the time and your initials, and a school keeps that book for five years.
You also check the calorifier is storing at sixty, you flush anything that is not used weekly, and once a year the little used outlets get a sample sent for culture.
The reason for the numbers is that legionella multiplies between about twenty and forty five degrees and dies above fifty, and the way you kill it is to make the water uncomfortable rather than to treat it. Which means a lukewarm tap is not a comfort problem, it is the problem.
Tap 4 in the old changing rooms reaches forty three degrees and stops.
Not forty three and then slowly up. Forty three after a minute, forty three after five, forty three after a quarter of an hour with the probe in it and me sitting on a bench reading the paper.
Everything else in that building reaches fifty two.
What was done about it in the proper order, because this is a documented trade and I have the paperwork for all of it.
Thermostatic valve. A blending valve that has failed sends lukewarm water, and it is the answer nine times in ten. Replaced in 2016, again in 2019, and the second one with a different make.
The tap itself. Replaced twice, and once with a plain pillar tap with no mixing in it at all, which means the water arriving is the water from the hot main.
The pipework, which is where this stops being plumbing. In 2015 that block was refurbished and the plumbing was redone, and the drawings from that job are in the file and I have walked them with the plumber who did it.
The old spur to the changing rooms was a dead leg, which is a length of pipe with no flow in it, and a dead leg is the thing my whole trade exists to remove. They cut it out. They took out about eleven metres of twenty two millimetre copper, capped the tee, and ran a new pipe on a different route.
So tap 4 is fed by the new pipe, which is fine everywhere else along its length.
The thing I measured in 2021 that I cannot put down.
I was chasing it with a thermal camera, which is not my kit but the maintenance man at that school has one for tracing underfloor heating.
You run the tap and you look at the wall, and you can see the hot pipe light up as the water moves through it.
The new pipe lights up. It comes in from the ceiling void, down the wall, to the tap.
So does the old route.
There is a line up that wall, about eleven metres of it when you follow it round the corner and along the corridor, that warms when that tap runs, and it is where the drawings say the dead leg was, and the plumber who took it out stood next to me and looked at it.
He said he remembered the job. He said he cut it out in two lengths and took it to the scrap man himself and got eighteen pounds for it.
The sample.
Part of the annual programme is a culture from the little used outlets, taken in a sterile bottle, couriered, and cultured for ten days by a laboratory.
Tap 4 has come back positive twice. Low counts both times, under a hundred colony forming units per litre, which is a result that means act rather than panic.
The action is a thermal disinfection: you take the calorifier up to sixty five and run every outlet for five minutes at the tap, which is an unpleasant job that you do wearing gloves with a sign on the door.
I have done that to tap 4 twice.
On both occasions I recorded the temperature at the tap throughout the disinfection, because you have to, and the temperature at tap 4 during a sixty five degree thermal disinfection was forty three degrees.
The tap next to it was sixty four.
And both times the follow up sample came back clear, which is the part that makes no sense at all, because nothing that happened at that tap should have killed anything.
What I do.
Tap 4 is on the schedule as a capped outlet now.
That is a real category and it is the honest answer to an outlet you cannot bring into specification: you take it off the system. The school's maintenance man and I did it in 2022. The tap came off, the pipe was cut back and capped properly behind the panel, and there is a blank plate on the wall and a line in the logbook and a sticker with the date.
I still test the block monthly because the rest of it is in use by the football club at weekends.
The only thing I do that is not in the manual is that I put the probe on the blank plate.
It is a magnetic surface probe, the kind you use on a pipe, and it reads the metal of the plate, and the plate reads about nineteen degrees, which is the temperature of that room.
Every month. Nineteen, twenty, eighteen in January.
Last month it read thirty one, and I wrote it in my own notebook rather than the logbook, because there is no column in the logbook for the temperature of a blank plate, and because the sentence I would have to write next is one I have no evidence for.