HIU servicing and repair, done by someone who knows them

In a block on district heating there is no boiler in your flat. Hot water arrives from a central plant and passes through a heat interface unit, which transfers that heat to your taps and radiators through plate exchangers.

It looks like a boiler, it is not one, and diagnosing it like one is why so many residents are told nothing is wrong while the shower stays lukewarm.

Lukewarm hot water that never gets hot is usually a scaled plate exchanger or a stuck actuator, not a fault with the network. Heating that works while the hot tap is off, and fails when it runs, points to a control valve.

Noise, hammering or a unit that never stops running are usually strainer or differential pressure problems. Each has a different fix, and none of them needs the whole unit replaced.

Annual service: strainers and filters cleaned, plate exchangers checked and descaled where needed, actuators and control valves tested, temperatures and differentials recorded before and after.

You get the readings. If your landlord or the heat network operator disputes that there is a problem, those numbers are the argument.

Where a unit is genuinely beyond economic repair, replacement is a half-day job in most flats and the network side rarely needs touching.

We will tell you plainly when a repair is the better option — replacing an HIU that needed a forty-pound strainer clean is depressingly common.