Low Water Pressure in Boiler

[albaqwerty]

just a general query really. Where does the water go?
I know it tootles round the system. Does it evaporate or leak somewhere?

[Old_Geezer]

It's the water nymphs. They turn the tap and let the water run out while you are sleeping.

[albaqwerty]

They're in cahoots with the sock monster then? :D

[The Builder]

I guess you mean on a Combi boiler, Alba?
Although it's a sealed system. There's inevitably a small loss somewhere over time. A slight leak on a connection somewhere (Ball-o-Fix isolating valves are a common reason) may not be always visible, but can reduce the amount of water in the system. The actual amount of water needed to re-fill from low pressure to full is quite small.
Also, if there's a fault in the boiler pressure vessel, the extra pressure in the system causes a safety valve to open and send water out through the pipe sticking out of the wall outside.

[albaqwerty]

Thank you TB x

Yep a combi-boiler. Needs topped up at least once a month. However, it's due it annual gas safety check so will be nagging at the gas-man.

[The Builder]

A part of the service should be to check the expansion vessel pressure. Mention your problem and ask him to re-charge it.

[paulthewall]

Hi Alba
havbe just noticed your Q and no-one has given you the correct answer, though the answer about leaks go part way.
Water is rarely neutral. Its pH may be one way or the other, and so it acts as an electrolyte and you get a very tiny amount of inter-reaction between the copper, brass and the iron in your boiler and rads. This causes gases to be given off, usually hydrogen and oxygen, but you are unlikely to get a stoicometric reaction, as there is no spark, so just let out the gas from the highest rad, and refill the system to about 0.5 bar, looking at the gauge on your boiler. Make sure you keep the rads free of air (gases) by monthly checking with a bleeding key. No, a key for bleeding.
Good luck.
Paul

[albaqwerty]

am very grateful to TB and to Paul (like the name)

Will be organising the annual check tomorow and let you know what's what.