primary system pressure dropping causes?

[staffordshireterrier]

have a quick question - what are the causes (possible causes) of a pressure gauge on a sealed primary system (eg combi) falling over time:

so far i can think of: seepage, slowly over time, leak somewhere in the pipework/rad valves/rads/aav, diverter valve, heat ex etc, inside boiler casing/prv dripping/expansion vessel problem/rads being vented ...

are there any else?

 

[Boilerman2]

Looks like you've got it covered!!!

 

[staffordshireterrier]

thanks

i heard a while ago (on here or ??) that hydrogen can cause the same problem??? just trying to think of any causes I might have missed?!!

 

[Paul Barker]

Yes hydrogen which naturally occurs escapes where water wouldn't so there is not a leak but there is a loss of pressure.

similarly after an initial install there is a loss of pressure as the trapped air finds it's way around the system and out.

Most common cause of pressure loss is the householder removing radiator to paint.

It is quite amaising how people who manage to feed and cloth themselves and get their children off to school in time to relax for the rest of the day in front of Jeremy Kyle, can't fathom a sealed system, or think to check the system controls at BST 1hr change forward or back, before callin in a breakdown "the boiler is on but the water isn't geting hot" which translated means the ready light is on but there is no call for heat because that will now come an hour later and when you say the water isn't hot you mean your radiators.

50% of the job is trying to establish what has actually happened after a barage of words which give you no clues.

also get ready for being looked at like you just talked martian when you asked where the controls are "where do you turn your heating on luv?" or where the ventilation is "oh that's it!" she says pointing at the chimney breast and looking at you as though you are a ******.. then you have to remove all the trinkets so they don't break of the tall display cabinate which is possibly stood on the floor vent, but disapointedly put it all back when you find it isn't, while she is on the phone to her gardner to come and interpret. He comes and joins in the attack "nobody has ever asked to see that before..... the bloke who put it in was very good!" "Well I don't think he was!"

Basically it's a war of wits!

 

[bengasman]

Pressure loss = some kind of leak somewhere.