Another heating "Engineer" story....
Mother-in-laws heating had its annual service by Worcester (or whatever they call themselves now), next morning there was no heat so another "Engineer" turns up and diagnoses low system pressure and re-pressurises it.
Next morning, no heat. New " Engineer" turns up and finds no pressure again so spends 3 hours looking for a leak, cant find one so re-pressurises it and leaves.
Next morning, no heat. Supervisor turns up, sees there is no pressure and says 'expansion vessel' which is changed lated that day.
Next morning, no heat. Supervisor plus one turns up, no pressure again and changes the heat exchanger.
Next morning, no heat. "Engineer" turns up and replaces the pump???
Next morning, no heat. I get up early and drive 35miles to MiL and simply look at the boiler etc. There is water on the ground under the pressure relief pipe. Re-pressurise the system and it lights up, second later a trickle of water appears at the pressure relief pipe.
Part of the service requires the pressure relief valve to be tested, most experienced plumbers / technicians know that they often leak once the valve lifts off its seat so they either fit a new seal or replace the valve as part of the service.
New valve clipped in and system holds pressure.
Worcester supervisor turns up and starts ranting about how I wasnt allowed to touch the boiler (combustion chamber etc not opened) then tried to say it voided her maitenance contract terms so I offered to write to his Director and appologise but also explain that an 87 year old woman was left without heating or hot water for 8 days because 4 different "Engineers" and one Supervisor couldnt follow a simple fault finding process. He backed off a bit then. (think I will write anyway).
MiL has a new heat exchanger, pump, fill valve, double check valve, pressure flush?

(Why?

?) fresh inhibitor and an overhauled pressure relief valve with new O rings.
Next morning, lovely and warm, and the next, and the next, until....
Next morning, no hot water. Flow switch has packed up. Man is on his way.
here we go again.