Boiler losing pressure

sakura11

I'm having intermittent problems with my combi boiler for over a month now.

The pressure drops (usually overnight) and we're having to top up the pressure at least once a day. 

It was serviced just under a month ago, and we were told there were no issues. 

Checked around the house and can't find any signs of leaks.

We've had a lot of water mains pipe leaks in our area, a couple resulting in total loss of water. Our supply seems to fine at the moment, but there are still ongoing leaks and repairs going on around us. 

Could it be the water mains problems causing our pressure to drop? 

Planning on getting an engineer out to check again, but it's hard to arrange as I'm working full-time. 

Hasbeen

Have you looked outside, at the pressure relief valve copper pipe outlet?  Usually on outside wall  at boiler position.  Any moisture?

Le_Kirk

sakura11 said:

I'm having intermittent problems with my combi boiler for over a month now.

The pressure drops (usually overnight) and we're having to top up the pressure at least once a day. 

We've had a lot of water mains pipe leaks in our area, a couple resulting in total loss of water. Our supply seems to fine at the moment, but there are still ongoing leaks and repairs going on around us. 

Could it be the water mains problems causing our pressure to drop? 

No, absolutely no connection between the two events or systems.  What pressure do you top it up to and what pressure does it drop to?

sakura11

Le_Kirk said:

sakura11 said:

I'm having intermittent problems with my combi boiler for over a month now.

The pressure drops (usually overnight) and we're having to top up the pressure at least once a day. 

We've had a lot of water mains pipe leaks in our area, a couple resulting in total loss of water. Our supply seems to fine at the moment, but there are still ongoing leaks and repairs going on around us. 

Could it be the water mains problems causing our pressure to drop? 

No, absolutely no connection between the two events or systems.  What pressure do you top it up to and what pressure does it drop to?

Top it up to about 1-1.5 (mid green zone on the gauge) and it drops completely to 0. I've had a radiator leak before, and the pressure would drop straight away as soon as I tried to use hot water or put heating on. Heating can be on for hours with no problem this time, and the pressure drops seem almost random. 

I will check outside as Hasbeen suggested. I wasn't at home when the engineer came to service it, but have been told he checked outside (although I'm not sure what he checked!)

sakura11

Hasbeen said:

Have you looked outside, at the pressure relief valve copper pipe outlet?  Usually on outside wall  at boiler position.  Any moisture?

Checked the pipe and no evidence of moisture.

Jeepers_Creepers

The 'heating on for hours with no problem' followed by 'pressure drop at random' points to water being dumped out the PRV, which is what's being alluded to above.

Have you definitely ID'd the correct 15mm copper pipe outside? Is it pointing down at the ground, or curved back on itself and facing the wall? Cool. Do you have a small clear plastic bag you can rubber-band around it until the next time the pressure falls?

That's the first test - please report back.

When the boiler is running, can you keep an eye on the pressure gauge too, please - see if it climbs at all when the rads are getting hot. What happens to the cold pressure of 1 to 1.5 you set it to? Does it climb? By much?

southcoastrgi

What boiler is it & how old ?

sakura11

Jeepers_Creepers said:

The 'heating on for hours with no problem' followed by 'pressure drop at random' points to water being dumped out the PRV, which is what's being alluded to above.

Have you definitely ID'd the correct 15mm copper pipe outside? Is it pointing down at the ground, or curved back on itself and facing the wall? Cool. Do you have a small clear plastic bag you can rubber-band around it until the next time the pressure falls?

That's the first test - please report back.

When the boiler is running, can you keep an eye on the pressure gauge too, please - see if it climbs at all when the rads are getting hot. What happens to the cold pressure of 1 to 1.5 you set it to? Does it climb? By much?

Small amount of water in the bag after having heating and hot water this morning. Pipe curves towards the wall.
Pressure goes up to 3 (engineer has previously told me that was fine). 
The heating has been off for almost an hour now and pressure has dropped to 1.5ish, now currently at 1. 

southcoastrgi said:

What boiler is it & how old ?

It's a Baxi one, not sure of model but can double check once I've finished work. Its almost 4 years old.

sakura11

Thank you so much for all of the comments and suggestions BTW! Really appreciate it!

Le_Kirk

If there is moisture in the bag, it suggests that the Pressure Relief Valve is passing.

Jeepers_Creepers

sakura11 said:

Small amount of water in the bag after having heating and hot water this morning. Pipe curves towards the wall.
Pressure goes up to 3 (engineer has previously told me that was fine). 
The heating has been off for almost an hour now and pressure has dropped to 1.5ish, now currently at 1. 

As Le_Kirk says, that's a Pressure Release Valve letting by. Which is good news since your pressure is hitting 3 bar (the max permitted safety level!)

Either you misunderstood your plumber when they said 3 bar was ok, or else he's a twit, because he is very wrong.

Of all the possible causes of a loss of water pressure, this is probably the best, as the other causes could be hidden leaks (causing fabric damage) and a bust main exchanger.

Anyhoo, you need a plumber to check and repressurise (or replace if it's found to be knackered) your Expansion Vessel, and then possibly replace your PRV if it keeps on dripping. (PRVs basically sit there for years until they are needed - ie when the pressure hits 3 bar. That blows them open, but the 'seat' of the seal has become so settled over these years that they often don't close again perfectly afterwards, or a bit of grit can land on them. If it carries on dripping after the repair, it'll likely need replacing.

If your system has lost a significant amount of water over the past while - ie you've been topping it up a lot - then you may wish to add fresh inhibitor to keep its strength up; you don't want corrosion in there.