Gradual loss of pressure in heating system

Theo_Cupier

We have a sealed, pressure system for our gas central heating (one of those big, red pressure balls in the airing cupboard).

Generally the heating is working fine, the rads get hot nice & quickly, TRVs keep them in check and the room thermostat in the hall controls the master on/off.

Per instruction we keep the system pressure at about 1 bar, according to the dial on the pressure ball. In truth, I usually top the system with water to slightly over 1 bar.

However, it needs topping up about once a fortnight because it gradually slips down to around 0.8 bar in that time. After I've topped the pressure back up with more water, I then have to bleed the radiator at the "top" of the system and then refill the system to sort the pressure again.

I've checked the seals on all the radiator valves (in & out) and can't find any obvious seepage in exposed pipework. The bleed points on all the rads are closed off well enough (tight enough to be shut but loose enough to open by hand).

My question is whether this is normal - to have the pressure gradually creeping downwards. In other words is this "nothing to worry about" and within acceptable tolerances (ie I should just live with it) or is it on the unhealthy side of the line, requiring more thorough investigation for leaks?

The system generally is quite new - condensing boiler and hot water tank are about 3 years old, but were relocated a year ago when we had some work done. Most of the TRVs were installed at the same time, although some are newer (due to failure). Several of the rads are only a year old but 4 others are much older.

belfastgirl23

We have this too - will be really interested to hear any responses!

BTW does yours go up to about 2 bar when the heat is on?

Canucklehead

Good morning: A sealed system shouldn't lose 0.2 bar pressure every two weeks. Leaks on rad valve spindles aren't always evident as the escaped CH fluid can evaporate during the heating season. You will be depleting the CH inhibitor every time you bleed the rads.
Check your AAV.

HTH

Canucklehead

Theo_Cupier

belfastgirl23 wrote: »

We have this too - will be really interested to hear any responses!

BTW does yours go up to about 2 bar when the heat is on?

Ours certainly rises in pressure when hot. 1.2bar cold usually equates to somewhere around 1.75bar hot.

Canucklehead - thank you but forgive my ignorance, what's an AAV (and how would I check it) since I'm guessing it's neither an Amphibious Assault Vehicle nor an Adeno-Associated Virus, which are the main results on Google(!)?

jscalow

mine does exactly the same. has done for 5 years with no other or further problems.

Canucklehead

Theo_Cupier wrote: »

Canucklehead - thank you but forgive my ignorance, what's an AAV (and how would I check it) since I'm guessing it's neither an Amphibious Assault Vehicle nor an Adeno-Associated Virus, which are the main results on Google(!)?

Hi....change your google search terms to boiler aav or central heating system aav ....the rest depends on your appliance...consult your manufacturer's installation guide if you have it (alternatively, documentation should be available on their website).;)

HTH

Canucklehead

Theo_Cupier

Thanks again. We don't have radiator AAVs. Not sure about the boiler. It has a pressure release vent for when the pressure gets above 3 bar in the system. The boiler is a Glowworm 18HXi, fwiw.

As I said, I've not noticed any water leaks from the radiators, so either it's a hidden pipe (but it must be downstairs since we don't have any worrying water marks on the ceilings) or the boiler AAV

Point noted about loss of inhibitor, but I guess if that's the only real concern, I'll struggle on for now. I'll just get Brit Gas to come around periodically to drain & refil the system to keep it topped up!


EDIT: Just looked through the installation manual for the boiler (link HERE) and there's no mention of autovalves...

Canucklehead

Theo_Cupier wrote: »

EDIT: Just looked through the installation manual for the boiler (link HERE) and there's no mention of autovalves...

Hi...the OH did install these but has given up on Glow-worm for numerous reasons. The discussion of your set-up (wonder why the installer didn't use an SXi i.e. system boiler instead)in Section 5.13 details requirements and the use of a safety valve....possible source of pressure loss/water blow-off.
You should get it sorted asap as sealed systems aren't designed for biweekly topping up/bleeding. Here is an excellent FAQ on sealed heating systems....also here

HTH

Canucklehead

Theo_Cupier

Thanks. Neither of the FAQs you point to seem too troubled by the idea of systems which lose pressure gradually. I don't find it too inconvenient so I'll leave it as an annual service issue to keep topped up and maybe suggest some leak sealant be added next time around .

Incidentally, the installer initially forgot to put the safety valve (5.13) in the system and it was losing pressure in the same way during that brief period. Now that the safety valve is in place it's not different.

Thanks again.

LJleaking

Hi,

I have red many of the problems listed on the forum and entirely sympathise. I have a combi Worcester 400 High flow and it has been serviced annually since it was first fitted 7 years ago. This winter and last, there was at least a 3 month period during which the pressure loss was so vast that the boiler stopped heating the radiators (it managed to heat hot water for taps however). During the summer this was not a problem. Both Worcester and British gas engineers have fully checked the boiler and have advised me there is a leak in the pipework. No leak could be detected and no water evaporation at valves and hence i was advised to get a leak detection company to inspect. "Munters" is a specialised company and they did two tests: a thermal image scan - no leak detected and then they drained the entire system and then introduced a special gas in to the system and use gas sensors to detect the leak - again no leak was identified. I am still adding approximately 2 pints of water at least every week and when it is really cold outside sometimes, every other day. The house was renovated and extended 7 years ago by the previous owners and i have no knowledge of how the ground floor heating pipes were laid (i understand if they were laid directly into concrete this can have a corrosive effect.

I am now at a complete dead end and not sure where to go from here.Worcester insist their boiler is not faulty. I am concerned there is a huge leak hiding beneath my concrete floor house. Any suggestions would be gratefully received. We are fed up with unreliable heating and being cold in the winter!
My family is desperate and my husband is loosing his hair with frustration.
Please HELP!

rockin_plumber

Theo_Cupier wrote: »

Incidentally, the installer initially forgot to put the safety valve (5.13) in the system and it was losing pressure in the same way during that brief period. Now that the safety valve is in place it's not different.

Thanks again.

:eek::eek::eek: I take it the installer explained the benefits of having this fitted


:eek::eek::eek: Put it this way potentially without it if something goes badley wrong with the system its :eek::eek:BOOM:eek::eek:

How someone can forget to fit a safety valve on a sealed system is beyond me :eek:

If the installer forgot to fit something as basic as a safety valve on a sealed system I would advise getting the rest of the system checked out ASAP!!



OOPS