Our new house has a year-old combi boiler. We are doing a lot of work in the house and 2 days ago early evening a bedroom radiator was lowered (pipes were frozen to do this) and a hall radiator was put back on after being off for a week due to decorating--all by our very good plumber.

Next morning I had a shower ok but when my wife got in no hot water!! Pressure gauge had dropped to zero so topped up and hot water again. Pressure dropped marginally by afternoon so topped up. All fine since. Can find no leaks in the system anywhere.

Could the initial radiator work I mentioned at the start of this HELP question be the cause? Having never had a combi with wall thermostat any help would be appreciated.


2 Answers 2


Absolutely: You may have not bled the radiator system enough so you have air bubbles in the primary loop.

To bleed a radiator:

  1. Open the valve
  2. Drain at least 2L of water after no more air is coming out

Repeat this for every radiator (air may have migrated).


Leaks to drop pressure slowly over time can be so difficult to locate - they may not even leave traces as the fluid can evaporate...

Check the connections of both of those radiators and get the system pressure tested.

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