Combi boiler losing pressure

[terryplumb]

If PRV is letting water out at "regular working" pressures, I guess it needs to be replaced?

Yes ,it would.

 

[TonerG1995]

What are you setting the pressure at when recharging? ( the setting in photo is ideal) Are you isolating taps on filling loop .

I set it to 1.5 bar. I believe I’m doing it correctly as I was shown how to by the person who installed it.

Before I had my leaking radiator replaced. The pressure would very often drop to 0 if left alone overnight. Since replacing my radiator, it does still drop but a lot slower. I tend to top it up when it falls just below 1 bar.

Correct me if I’m wrong, but a good working boiler wouldn’t drop from 1.5 to 1 in the space of a few days, right?

 

[opps]

That’s interesting, thank you! Say there is a leak in the pipes under the ground floor…I’m assuming that would require a significant amount of invasive work??

Do you lose pressure over warm weeks when the heating is not on?

I have worked in a number of houses where the regular cold pressure is set at 1.5 bar, but when the heating is on, it jumps up to 3+ bar.

It may, or may not be the case that any leak only occurs when the pressure is high. I have seen additives that claim to be able to plug tiny holes but would not recommend that you use them without first talking to a proper plumber such as @terryplumb

 

[opps]

I set it to 1.5 bar. I believe I’m doing it correctly as I was shown how to by the person who installed it.

Before I had my leaking radiator replaced. The pressure would very often drop to 0 if left alone overnight. Since replacing my radiator, it does still drop but a lot slower. I tend to top it up when it falls just below 1 bar.

Correct me if I’m wrong, but a good working boiler wouldn’t drop from 1.5 to 1 in the space of a few days, right?

How long does it take to drop so low that the boiler will not function? How many rooms/rads do you have?

The above may help others to advise you further.

 

[TonerG1995]

Do you lose pressure over warm weeks when the heating is not on?

I have worked in a number of houses where the regular cold pressure is set at 1.5 bar, but when the heating is on, it jumps up to 3+ bar.

It may, or may not be the case that any leak only occurs when the pressure is high. I have seen additives that claim to be able to plug tiny holes but would not recommend that you use them without first talking to a proper plumber such as @terryplumb

Yep - we lose pressure all year round. When we put the heating on, it jumps to 1.8-2ish bar. Then very quickly settles back around 1-1.5 bar once it’s been switched off.

 

[TonerG1995]

How long does it take to drop so low that the boiler will not function? How many rooms/rads do you have?

The above may help others to advise you further.

It’s never stopped functioning before, not since we replaced the radiator anyway. I imagine it probably would drop to 0 eventually however it’s become a part of my morning routine to check the pressure and if it ever falls below 1 bar, I top it back up to 1.5.

It’s a 4 bedroom house with 10 radiators.

 

[foxhole]

There is no need to pressurise until it’s near zero .

 

[TonerG1995]

There is no need to pressurise until it’s near zero .

That’s good to know, thank you. Is it common for a boiler to drop from 1.5 bar to 1 in the space of a few days? Maybe I’ve been overthinking…

To be fair, I’ve never left it to really drop to zero, perhaps I should see what happens. Maybe it drops to .9(ish) then stabilises?

As you can all tell, I’m a rank amateur at all of this!

 

[foxhole]

That’s good to know, thank you. Is it common for a boiler to drop from 1.5 bar to 1 in the space of a few days? Maybe I’ve been overthinking…

To be fair, I’ve never left it to really drop to zero, perhaps I should see what happens. Maybe it drops to .9(ish) then stabilises?

As you can all tell, I’m a rank amateur at all of this!

The more pressure the more chance of leaking , if it’s a tiny weep somewhere on pipework it may run happily at lower pressure without further loss.

 

[TonerG1995]

The more pressure the more chance of leaking , if it’s a tiny weep somewhere on pipework it may run happily at lower pressure without further loss.

Brilliant - thank you. I’m going to leave it alone then and see if/where the pressure stabilises.

 

[cdbe]

Presumably a new boiler on an older vented heating system. It's now running at a higher pressure and can leak at any weak point (more so when hot and the pressure increases more). Weak points are generally badly soldered joints, loose compression fittings or pinholes (tiny rust holes) in radiators. In a slow leak the water can often evaporate, including from an ceiling, with little or no evidence (the dripping etc you're probably looking for) - look for rusty radiators, slightly damp patches in ceilings and staining on the pipes and fittings at the radiators. If you find nothing and have ruled out leaking heat exchanger and escape from prv you're probably looking at under/in ground floor - if solid then it's trying to trace leaks with thermal cameras etc or often just abandon old pipes and re pipe on the surface.

It's not normal to have to top it up - you'll dilute your inhibitor and may have air in the system, both will wreck the boiler and radiators.

I don't know about running it at lower pressure, I believe most manufacturers recommend a minimum pressure of 1 bar - but I don't know what the consequences are, maybe excessive air, or pump problems, or nothing!

 

[TonerG1995]

Presumably a new boiler on an older vented heating system. It's now running at a higher pressure and can leak at any weak point (more so when hot and the pressure increases more). Weak points are generally badly soldered joints, loose compression fittings or pinholes (tiny rust holes) in radiators. In a slow leak the water can often evaporate, including from an ceiling, with little or no evidence (the dripping etc you're probably looking for) - look for rusty radiators, slightly damp patches in ceilings and staining on the pipes and fittings at the radiators. If you find nothing and have ruled out leaking heat exchanger and escape from prv you're probably looking at under/in ground floor - if solid then it's trying to trace leaks with thermal cameras etc or often just abandon old pipes and re pipe on the surface.

It's not normal to have to top it up - you'll dilute your inhibitor and may have air in the system, both will wreck the boiler and radiators.

I don't know about running it at lower pressure, I believe most manufacturers recommend a minimum pressure of 1 bar - but I don't know what the consequences are, maybe excessive air, or pump problems, or nothing!

Thank you for this!

Last year I had a leak in my kitchen ceiling however the plumber who came couldn’t find any pipes running through the kitchen ceiling and instead found water had been pooling from the bath and coming through the floor which he then sorted and has been fine ever since.

Is there any chance he’s overlooked something?

The thought of having my carpets and/or floorboards torn to pieces is giving me nightmares! Although if it needs doing, it needs doing…

 

[TonerG1995]

Evening guys,

Just a quick update on this. The bag I placed around the pipe outside is bone dry so I’m assuming it’s not that?

Bit of a silly question but do water pipes run along the walls and edges of the house, or could they be in the middle of the ceiling/flooring? I’m going to see if I can find a leak elsewhere as none of my radiators are leaking and the pipe work I can see all seems to be perfectly dry. Would bleeding the radiators help? I know this will initially make the boiler pressure lower but in the long run, could that be the issue? There’s one radiator I had trouble getting to in my house. It hasn’t leaked but positionally it’s quite difficult to bleed.

Since last updating you, my boiler pressure is currently at 0.9 bar…so it must be dropping off somewhere?!

I’m going to get a plumber in anyway, which may well take months as my council are useless, but I want to eliminate every possibility before that!

 

[terryplumb]

Is your ground floor concrete or suspended timber ?
Where is your boiler , ground floor or upstairs ?
Heating pipes can run in various locations.

 

[TonerG1995]

Is your ground floor concrete or suspended timber ?
Where is your boiler , ground floor or upstairs ?
Heating pipes can run in various locations.

Ground floor is concrete and boiler is downstairs in the kitchen