Pressure loss from sealed system stops when open/closing a zone with 'a leak'

[woodstock1968]

Hello all,

Seeking any input on a matter that seems to defy logic and common sense.

Sealed system Oil fired boiler (newish) feeding a large farmhouse from an annex with a good quality install/ pump etc that seems to be doing the job.
The system is losing 1 bar per day for a long time. I isolated the flow return in the entrance to the house and left for 24 hours, the pressure did not move, so presumed copper pipe leak undergrounds in the concrete.
Then I thought to make sure the flow /return I had isolated fed all the rads in that house, I turned on the heating and low and behold it only isolated 5 rads in the kitchen and utility room area.

I then as a stop-gap before further underground leak exploration I advised that the system would hold the pressure if the 5 rads in the kitchen area were isolated, and that is exactly what happened, the heating was used and the pressure bar did not move whilst the heating was on for the rest of the house.

Spin-on another week and I then was informed that due to extreme cold the isolating valves feeding the kitchen/utility room was being turned on/off just prior and just after the heating was turned on/off.
Now the Bar pressure has not dipped at all, and no top-ups had been carried out? Surely the leak (if that is the issue) would continue with/without the iotation and when flowing again that would shoot the pressure downwards instantly; It hasn’t?


With thanks in advance, can anyone understand why the system is not losing any pressure once the kitchen/utility area isolation valves are opened up and flowing and offer up any scenario that I may be incorrect with my underground leak theory?



Confused.



Many thanks

 

[Brambles]

You really need to sketch out the full system ( flow and return paths) to the best of your ability - from what you can see and the information from the tests conducted to date. You have already had one surprise when an isolation did not cut off a set of radiators - there are probably one or two more lurking there too.

If you start off with an indicative plan, all the future tests you do will build up the detail and information in a structured manner. Leak investigation in an adhoc manner is frustrating and does not always deliver results.

Be aware that a leaking pipe encased in screed / concrete does not always leak at a consistent rate - I don’t know why!!

Also worth estimating the volume of water loss that a 1 bar drop on the system leaks - at least then you know what the scale of what you are looking for represents.

Be wary of using a leak detection specialist - never good value for money in my experience