Boiler losing pressure

jollyj1984

Hey,

The usual story of boiler losing pressure over time.

I top up to 1.2 bar and over 2-3 months it drops to under 0.5 bar and needs topping up.

It's obviously a slow leak and I've tried the tricks of checking radiators and prv outside.

Is it worth calling an engineer which could cost alot on investigating and ultimately finding nothing or am I better of waiting until it gets worse?

My 2 worries are inhibitor level from The topping up 4-5 times a year and the damage to any joist from the leak etc.

 

strawberries1

Might need expansion vessel checked for water and then filled with air; filter and pipe in boiler cleaned. That helped mine.

jollyj1984

strawberries1 said:

Might need expansion vessel checked for water and then filled with air; filter and pipe in boiler cleaned. That helped mine.

If it was the expansion vessel would the pressure not increase wildly when heating is on? Which it doesn't. 

jollyj1984

Additional information I can give is....
It's a potterton promax combi
It seems to drop pressure more when heating is on. 
There was a leak on the heating return valve that we tightened and siliconed around, no signs this is leaking now. 
Pressure sits at 1.1 bar cold and increases to around 2.2 when fully operating. 

Jeepers_Creepers

jollyj1984 said:

Pressure sits at 1.1 bar cold and increases to around 2.2 when fully operating. 

That does indicate an expansion vessel issue - that climb is a tad too high - or a bit too 'wild' to quote yersel' :-).

It probably just needs checking and recharging. Are you up for this? If so, do a surf for how, and come back if you have any concerns.

You've checked the discharge pipe, tho' - the 15mm copper one pointing at the ground, or back against the wall? Are you 100% certain? Tied a small plastic bag over it?

jollyj1984

Jeepers_Creepers said:

jollyj1984 said:

Pressure sits at 1.1 bar cold and increases to around 2.2 when fully operating. 

That does indicate an expansion vessel issue - that climb is a tad too high - or a bit too 'wild' to quote yersel' :-).

It probably just needs checking and recharging. Are you up for this? If so, do a surf for how, and come back if you have any concerns.

You've checked the discharge pipe, tho' - the 15mm copper one pointing at the ground, or back against the wall? Are you 100% certain? Tied a small plastic bag over it?

It's hard to describe, the heating system is split and controlled by 2 thermostats (up and downstairs) if its just the downstairs heating on it pretty much sits at the same as the cold pressure, but if both up and down are on if rises up to the 2.2 bar. 

I've checked the 15 mm pipe a few times and it all looks dry, I've never seen the gauge go into the red.

 If it is the expansion vessell and it's not pushing water out the overflow, how would this cause the pressure drop? 

Jeepers_Creepers

jollyj1984 said:

It's hard to describe, the heating system is split and controlled by 2 thermostats (up and downstairs) if its just the downstairs heating on it pretty much sits at the same as the cold pressure, but if both up and down are on if rises up to the 2.2 bar. 

I've checked the 15 mm pipe a few times and it all looks dry, I've never seen the gauge go into the red.

 If it is the expansion vessell and it's not pushing water out the overflow, how would this cause the pressure drop? 

You obviously have a good handle on what's going on. As you say, the pressure would usually need to reach around 3 bar before the Pressure Release Valve is opened to release the excess pressure - that would certainly lead to a fall in cold pressure. However, at 'only' 2.2bar, the system should be ok and not lose water. (But still worth rubber-banding a small clear bag over the end tobesure tobesure).

Why does your system pressure only rise to 2.2 bar when both zones are employed? Haven't a scooby. Nothing comes to mind that would double the system pressure only when a second zone is called in. Both zones are connected via their communal return pipes anyway, so what happens in one should happen in the other. And if, for example, there was a rad up there with a huge amount of air inside it, this would only help to keep the system pressure more constant - it would add as a second EV!.

Sorry, Jolly - I'm stumped.

Stick that bag on, tho' :-)

jollyj1984

Jeepers_Creepers said:

jollyj1984 said:

It's hard to describe, the heating system is split and controlled by 2 thermostats (up and downstairs) if its just the downstairs heating on it pretty much sits at the same as the cold pressure, but if both up and down are on if rises up to the 2.2 bar. 

I've checked the 15 mm pipe a few times and it all looks dry, I've never seen the gauge go into the red.

 If it is the expansion vessell and it's not pushing water out the overflow, how would this cause the pressure drop? 

You obviously have a good handle on what's going on. As you say, the pressure would usually need to reach around 3 bar before the Pressure Release Valve is opened to release the excess pressure - that would certainly lead to a fall in cold pressure. However, at 'only' 2.2bar, the system should be ok and not lose water. (But still worth rubber-banding a small clear bag over the end tobesure tobesure).

Why does your system pressure only rise to 2.2 bar when both zones are employed? Haven't a scooby. Nothing comes to mind that would double the system pressure only when a second zone is called in. Both zones are connected via their communal return pipes anyway, so what happens in one should happen in the other. And if, for example, there was a rad up there with a huge amount of air inside it, this would only help to keep the system pressure more constant - it would add as a second EV!.

Sorry, Jolly - I'm stumped.

Stick that bag on, tho' :-)

Most of it goes over my head to be honest! I have a basic understanding of how it all works but maybe it's time for a professional to look. 

Somone mentioned to me that it could be a small leak on the main heat exchanger which obviously I can't access myself as not gas Safe 

Like I say it seems to take about 2-3 months to lose 0.7 bar and cut out so maybe waiting for some kind of evidence to appear on the ceiling etc if the leak is on the pipe work. 

I could literally remove every floorboard trying to find a weep. 

Jeepers_Creepers

You'd struggle to find a leak in a main exchanger even if you took it apart! That sort of leak will escape via the condensate pipe, so hard to judge.

There are some basic tests you can run through, if you are up for it. Under the boiler you will find all the pipes coming in - two of these, in 22mm copper - will be the CH flow and return. They will have isolating valves on them where they join the boiler. If you pressurise your boiler to, say, 2 bar, shut it off completely (ie via its power supply) and then close off these two valves, you can monitor the pressure and hopefully see whether the leak is from within or without the boiler itself.

You leave it for at least a day or so (so not very practical) and then check the pressure. If it's fallen, that would suggest an internal leak (the PRV or a cracked exchanger). If it's constant - but then drops as soon as a valve is reopened, that suggests a leak on the rad and pipework system.

Jeepers_Creepers

Do you have a magnetic filter fitted? If so, that's an easy way to introduce a dose of system sealant - I guess no harm in trying.

jollyj1984

Jeepers_Creepers said:

You'd struggle to find a leak in a main exchanger even if you took it apart! That sort of leak will escape via the condensate pipe, so hard to judge.

There are some basic tests you can run through, if you are up for it. Under the boiler you will find all the pipes coming in - two of these, in 22mm copper - will be the CH flow and return. They will have isolating valves on them where they join the boiler. If you pressurise your boiler to, say, 2 bar, shut it off completely (ie via its power supply) and then close off these two valves, you can monitor the pressure and hopefully see whether the leak is from within or without the boiler itself.

You leave it for at least a day or so (so not very practical) and then check the pressure. If it's fallen, that would suggest an internal leak (the PRV or a cracked exchanger). If it's constant - but then drops as soon as a valve is reopened, that suggests a leak on the rad and pipework system.

That's a great idea to test the boiler vs the pipework. My only concern is that because it's such a small leak would it show a pressure drop in a day with the valves closed? Sometimes i dont see any loss for about a week