Pressurised Plumbing System - Question

jwb1

We recently got our existing heating system pressurised in order to let the boiler feed some new radiators in an extension that we are adding to the house.

When the plumber set the thing going initially, the pressure gauge was reading about 2 bar. Over the first night, it dropped pretty quickly to about 1.5 bar. It held around there for about 4-5 days and now, in the last couple of days, I can see it slipping back a little bit more.

2 questions on this: (1) I presume this change in pressure suggests leak of some form somewhere in the system? and (2) what minimum should the pressure be anyway? Someone told me that even 0.5 bar is sufficient.

Any advice very much appreciated.

joeduggan

jwb1 wrote: »

We recently got our existing heating system pressurised in order to let the boiler feed some new radiators in an extension that we are adding to the house.

When the plumber set the thing going initially, the pressure gauge was reading about 2 bar. Over the first night, it dropped pretty quickly to about 1.5 bar. It held around there for about 4-5 days and now, in the last couple of days, I can see it slipping back a little bit more.

2 questions on this: (1) I presume this change in pressure suggests leak of some form somewhere in the system? and (2) what minimum should the pressure be anyway? Someone told me that even 0.5 bar is sufficient.

Any advice very much appreciated.

yeah it does sound like a leak. and the pressure should be at one bar when the heating is off and cold

It could be a bit of air in the in the system as well, i would refill the system up to about 1 1/2 bar and monitor the pressure drop, look for the discharge pipe outside and tape a plastic bottle to it or put a bit of tissue up the pipe, this will tell you if any water is passing the discharge valve. You may find that you do have a leak and if so you should think about having the water checked in the rads and if contaminated flush the system and adding a inhibitor once the problem is dealt with, Gary.

jwb1

gary71 wrote: »

It could be a bit of air in the in the system as well, i would refill the system up to about 1 1/2 bar and monitor the pressure drop, look for the discharge pipe outside and tape a plastic bottle to it or put a bit of tissue up the pipe, this will tell you if any water is passing the discharge valve. You may find that you do have a leak and if so you should think about having the water checked in the rads and if contaminated flush the system and adding a inhibitor once the problem is dealt with, Gary.

When you say "discharge valve", do you mean the pressure regulator valve? And would the "discharge pipe" be where the old overflow pipe from the expansion tank was?

Finally, what's an "inhibitor"? The plumber has mentioned using some sort of liquid (or powder?) leak sealer...just add it to the system and - whoosh! - all small leaks eliminated - is this credible?

Thanks for your help....

Joey the lips

It might be nothing, Did you notice the pressure when the system was off or on. It flucuates due to the heat. Seriously, dont go near it till it stops working. The old rule applies, if its not broken....

ps: if he used inhibitor and leaksealent chances are what he has done is cleaned the system then applied inhibitor. When he repressurised it some leaks came through so he used leaksealent. Normal practice imo.

Gurgle

jwb1 wrote: »

When the plumber set the thing going initially, the pressure gauge was reading about 2 bar. Over the first night, it dropped pretty quickly to about 1.5 bar. It held around there for about 4-5 days and now, in the last couple of days, I can see it slipping back a little bit more.

2 questions on this: (1) I presume this change in pressure suggests leak of some form somewhere in the system? and (2) what minimum should the pressure be anyway? Someone told me that even 0.5 bar is sufficient.

Might not be a leak, just air making its way out of the system.
Turn on the mains filler and bleed all the radiators.

The minimum pressure isn't so important as having the system full of water, the pressure you see on the dial (once you've turned off the mains fill) depends on the weight of water above the dial and the temperature of the water.

Even with a perfectly sealed system it will vary with temperature.

jwb1

jwb1 wrote: »

When you say "discharge valve", do you mean the pressure regulator valve? And would the "discharge pipe" be where the old overflow pipe from the expansion tank was?....

No, with a pressurized system you have a pressure relief valve(discharge valve) fitted, this is a valve designed to release system pressure if it rises above 3 bar, it will open and release the pressure/water to a safe place normally outside via a pipe fitted to it the release valve, the valve can be inside a boiler or retro fitted to the heating pipework if the boiler hasn't got one, you can lose pressure threw the valve and not see it, buy fitting a bottle to where it terminates it's easier to determine if the valve is holding pressure.

jwb1 wrote: »

Finally, what's an "inhibitor"? The plumber has mentioned using some sort of liquid (or powder?) leak sealer...just add it to the system and - whoosh! - all small leaks eliminated - is this credible?..

If you have a look at the sentinel site http://www.sentinel-solutions.net/en/heating/X100 you will get better info, but inhibitor is a chemical that will prevent the build up of sludge, very, very few installers will flush a system properly and add a inhibitor on installation of a new boiler, so most heating installations aren't protected and adding fresh water all the time to a unprotected heating system is not healthy, Gary.

PeteHeat

Hi,

Is the boiler gas or oil ?

Reason I ask is some gas boilers need a minimum .5 > 1 bar.

There may be a bottle vent fitted which will release air from the system over time hence the slow drop in pressure.

I would not recommend interfering with the safety valve or topping up your system, monitor the pressure if it drops to 1 bar call the plumber who installed the system.

I would expect he had a reason for leaving a cold system with 2 bar pressure.

.

jwb1

Joey the lips wrote: »

It might be nothing, Did you notice the pressure when the system was off or on. It flucuates due to the heat. Seriously, dont go near it till it stops working. The old rule applies, if its not broken....

ps: if he used inhibitor and leaksealent chances are what he has done is cleaned the system then applied inhibitor. When he repressurised it some leaks came through so he used leaksealent. Normal practice imo.

Well, it seems to be holding at 1.4 bar when hot and just sitting at 1.0 bar when cold. I'll have to ask about the inhibitor stuff....thanks.

PeteHeat wrote: »

Hi,

Is the boiler gas or oil ?

Reason I ask is some gas boilers need a minimum .5 > 1 bar.

There may be a bottle vent fitted which will release air from the system over time hence the slow drop in pressure.

I would not recommend interfering with the safety valve or topping up your system, monitor the pressure if it drops to 1 bar call the plumber who installed the system.

I would expect he had a reason for leaving a cold system with 2 bar pressure.

.

It's a Potterton gas boiler. To be accurate, it was 2 bar when hot. Then, over about 4-5 days, it dropped back to 1.5 when hot, then 1.4 and now it appears to be holding steady at that.

Joey the lips

imo it working fine. Leave it alone till it does otherwise.