boiler pressure paranoia

[chrisw99]

I had a new boiler fitted last December, a combi to replace an ancient gravity fed system. I read lots of horror stories about old systems possibly springing leaks due to the increased pressure, also I have a mild form of OCD which means I can't stop monitoring it.

It was set at 1.2 bar, exactly on the line, when the system was cold (there's a digital display on the boiler telling you the water temperature - in the mornings when the heating has not been I always make sure this reading is the same when I check the pressure gauge).

Over a few weeks, this drops by extremely tiny amounts, no longer exactly at 1.2 but maybe 1.18. I crack open the top up tap fractionally for literally half a second to get it back dead on the line. No more than a thimble full of water was probably added.

When you read about leaks on here, people talk about it dropping 0.5 bar in a week or two. Ours has probably dropped 0.2 bar in the 9 months we've had it, so I'm not unduly worried about a major leak, it's just that bloody OCD of mine doesn't like it changing!

Oh and the boiler manual mentions it has a natural air bleed valve on the pump so check and top up the pressure every few months, but being me I choose to ignore that face and still get paranoid I have a leak. (because the heating hasn't been on for 3-4 months so the pump hasn't been running).

So - is such a tiny drop (0.2 over 9 months) anything to worry about, or do boilers naturally lose extremely small amounts of pressure over time??

 

[Nige F]

No don't worry about it That's from a retired plumber with OCD like yourself - I wasn't fast but I was thorough with my work, that was the reason. The gauge isn't likely to be scientifically accurate. Follow the manual's instructions and fight the urge, good luck

 

[muggles]

There's a certain amount of hysteresis in the pressure gauges so they won't always return to where they started, and as you've mentioned yourself there's an auto air vent on most boilers which will allow air out, causing pressure drops. If you have a leak, there will be a wet patch somewhere. If there's no wet patch, there's no leak

 

[fixitflav]

I had a new boiler fitted last December, a combi to replace an ancient gravity fed system. I read lots of horror stories about old systems possibly springing leaks due to the increased pressure, also I have a mild form of OCD which means I can't stop monitoring it.

It was set at 1.2 bar, exactly on the line, when the system was cold (there's a digital display on the boiler telling you the water temperature - in the mornings when the heating has not been I always make sure this reading is the same when I check the pressure gauge).

Over a few weeks, this drops by extremely tiny amounts, no longer exactly at 1.2 but maybe 1.18. I crack open the top up tap fractionally for literally half a second to get it back dead on the line. No more than a thimble full of water was probably added.

When you read about leaks on here, people talk about it dropping 0.5 bar in a week or two. Ours has probably dropped 0.2 bar in the 9 months we've had it, so I'm not unduly worried about a major leak, it's just that bloody OCD of mine doesn't like it changing!

Oh and the boiler manual mentions it has a natural air bleed valve on the pump so check and top up the pressure every few months, but being me I choose to ignore that face and still get paranoid I have a leak. (because the heating hasn't been on for 3-4 months so the pump hasn't been running).

So - is such a tiny drop (0.2 over 9 months) anything to worry about, or do boilers naturally lose extremely small amounts of pressure over time??

On a combi the pump will have been running during the summer, when you've used hot water. So even less reason to worry!

 

[Londoner2]

Normal, nothing to worry about.

My old boiler wb combi (21 years old) used to lose pressure over a few months by 0.5, used to top it up, now it seems ok, in oct i test the heating and bleed rads and top up as required to get pressure above 1bar.

 

[muggles]

On a combi the pump will have been running during the summer, when you've used hot water. So even less reason to worry!

Unless it's an Intergas

 

[fixitflav]

Unless it's an Intergas

How does the Intergas do it then? Always glad to learn something!

 

[Dan Robinson]

Unless it's an Intergas

There's always the pump exercise function though

 

[muggles]

How does the Intergas do it then? Always glad to learn something!

The water flows through a flow switch, which fires up the boiler, and through the hot water circuit of the single heat exchanger. The water is heated directly rather than via a secondary plate heat exchanger, so there's no need to run the pump because primary water isn't required to heat the domestic side. This means the pump suffers considerably less wear and tear than it would on other combi boilers, because it's not used anywhere near as much

 

[fixitflav]

The water flows through a flow switch, which fires up the boiler, and through the hot water circuit of the single heat exchanger. The water is heated directly rather than via a secondary plate heat exchanger, so there's no need to run the pump because primary water isn't required to heat the domestic side. This means the pump suffers considerably less wear and tear than it would on other combi boilers, because it's not used anywhere near as much

OK thanks

 

[John D v2.0]

crack open the top up tap fractionally for literally half a second to get it back dead on the line.

If it really does lose noticable pressure with such a tiny amount of water then check your expansion vessel charge pressure. It should be slightly below the cold fill pressure, even 0.1 is enough. The only trouble isis you should really drain the boiler to make it correct and it may be inside the casing anyway so inaccessible to mere mortals.

there's a digital display on the boiler telling you the water temperature

That's the temperature of the primary water in the boiler, but the water everywhere in the system affects the pressure. Unless you have the pump running for a while before checking it may have different temperatures thought the system.