Re-pressurising heating system - water leak or air intake?

[Gary_M]

Hi,

Thanks to Chrishutt for advice on a previous post I made relating to this problem (clicking noise in radiator). I have checked 'manually' for any possible leaks, but can't find any. Think I will need to get a pressure test organised.

My question is: As the pressure in my system is dropping to almost 0 every 2 weeks or so, I am having to add new water to re-pressurise it. Does this usually mean that air is coming into the system or water is leaking out? Most of the piping is unfortunately under the floor, so it's not so easy for me to check, but there is no sign of any water leaks at any of the joints, valves, pump, boiler, etc

The boiler (which is actually less than 3 months old) is working fine and the pump (can't recall make - also less than 3 months old) is working perfectly too.

Thanks

 

[chrishutt]

Water is obviously leaking out, but when the pressure drops to zero it becomes possible for air to enter as well. No point in having a pressure test - you already know you have a leak.

The water leak(s) is either in the system or the boiler. In the system the most likely points are the rad valves, particularly around the spindles which are usually concealed under a plastic cap. On the boiler the PRV may drip and this would be visible at the end of the discharge pipe, usually on the outside wall a metre or so below the flue terminal. The AAV may also leak within the boiler. Also check the inlet valves below the boiler.

You could determine whether the leak is on boiler or system by leaving the heating off for a while (maybe not right now!) and closing the isolating valves on the flow and return pipes below the boiler. Then if the pressure gauge shows a drop over time the leak is within boiler, if not it must be the system. Note what happens to pressure when you reopen the iso valves. If it drops suddenly this confirms leak in system pipework.

You should really get the boiler installer to check this out under guarantee.

 

[Gary_M]

Thanks again Chris.

There is certainly no evidence of water around any of the places you mentioned. I have been checking at least daily, and would have thought there might have been some signs of water - I have even used a kitchen towel to wip around the valves, pipes under boiler, etc - but nothing.

I was just thinking of using a pressure test to determine where the leak might be, but I'll get hold of the guys that installed it - as you say, it's still under guarantee, so really they should be checking things out

Thanks again

 

[Gary_M]

Follow Up

I'm currently waiting for the plumbers who installed to come out and check my system (due at the end of next week).

In the meantime, I think I have traced the leak. I noticed a very small amout of water on top of one of the valve spindles. I put a little extra pressure into the system to see what happened, and this pool definitely got bigger.

As the problem is getting worse (dropping from Just over 1 bar to almost 0 in 2 days), could anyone tell me if such a 'relatively' small leak could be the sole cause of such a pressure drop?

Of course, I'll leave it until the guys come next week, but I would be interested to know

Thanks

 

[croydoncorgi]

With a typical expansion vessel for a 4-bed house or large apartment, going from 1 Bar to zero is usually equivalent to between 2 and 3.5 litres of water lost from the system.

But that assumes that the expansion vesel is working properly.....