Vaillant combi boiler low water pressure

[PhilW]

I have a Valliant Turbo Max combi boiler about 8 years old. Recently the water level has dropped below 0.8 Bar some days, usually at night, so I have have had to top it up in the morning. I thought it might be a leak in the system but there's no sign of one anywhere and also the problem is somewhat erratic, so if there were a leak you would expect it be the same very day. I noted that the water and heating temperature were both almost up to the maximum, during a very cold spell, so I have turned them down, which seems to have solved the problem So could this be the reason why the level kept dropping or is it just coincidence?

PhilW

 

[A Drip]

The best way to determine where the leak might is to turn the heating programme off over night and in the morning if the pressure has dropped then the problem is within the boiler possibly the pressure vessel . to check this out find the dust cap on the above remove it ,depress the internal valve and if water comes out then you will need to get a new pressure vessel it could even be a sem leaking around the vesse. Have you checked the Auto Air Vent this could be letting by and causing the same problems. The pressure loss fluctuation is most probably due to the temperature. ie Pressure is inverly proportional to it's temperature.

 

[bewsh]

If you turn the programmer off and the pressure still drops then it doesn't mean its in the boiler, it could still be on the radiators? Have you noticed any damp patches near the radiators?

With regards to the expansion vessel, it's not very often that the rubber diaphragm has failed as it's pretty thick and strong, usually it's just lost it's air pressure - even if you have water coming out of the schrader valve, it's usually just a build up of condensation - you need to get in a gsr engineer to recharge the vessel correctly (if that is the fault)