No you don't have a hole in the diaphragm. If you did, water would pass across and the volume on the 'air' side would be reduced. This would result in the pressure going high, except the prv would operate.
It is feasible that air pressure is sometimes lost at the schrader valve and checking the air pressure is basically a service requirement.
What is important just as much as the pressure is the vessel should be full of air to give minimum increase in pressure. That is why the water side must have zero pressure and open to atmosphere when vessel is charged.
Your readings of 1.7 to 2.6 are to be expected. If you think the 2.6 is getting too near the 3bar to operate the prv why not drop the 1.7 down. you could have it at 1.1bar rising to 2.0bar.
Remember when the prv operates due to fault the pressure would drop from 3bar down to about 0.5 bar in a second.
Your problem is a small drop over a longish period when cold, so obviously there is small continuous leaksomewhere
I agree if the schader valve was losing air and the excess water was passing into the expansion vessel, you would not see it. But you would eventually see the 2.6 pressure rising until it reached the 3bar.
The most likely place for the leak is the prv not seating properly after having been opened. Again you may not see it, it may have evaporated before it reaches the open end of the discharge pipe.
Then there's the automatic air valve
Other than those it's a leak in the system pipe work/radiators.
Valve spindles is a likely culprit, sometimes leak when cold but stop leaking when hot. worth just testing/tightening the packing gland nut on the new valves
It is feasible that air pressure is sometimes lost at the schrader valve and checking the air pressure is basically a service requirement.
What is important just as much as the pressure is the vessel should be full of air to give minimum increase in pressure. That is why the water side must have zero pressure and open to atmosphere when vessel is charged.
Your readings of 1.7 to 2.6 are to be expected. If you think the 2.6 is getting too near the 3bar to operate the prv why not drop the 1.7 down. you could have it at 1.1bar rising to 2.0bar.
Remember when the prv operates due to fault the pressure would drop from 3bar down to about 0.5 bar in a second.
Your problem is a small drop over a longish period when cold, so obviously there is small continuous leaksomewhere
I agree if the schader valve was losing air and the excess water was passing into the expansion vessel, you would not see it. But you would eventually see the 2.6 pressure rising until it reached the 3bar.
The most likely place for the leak is the prv not seating properly after having been opened. Again you may not see it, it may have evaporated before it reaches the open end of the discharge pipe.
Then there's the automatic air valve
Other than those it's a leak in the system pipe work/radiators.
Valve spindles is a likely culprit, sometimes leak when cold but stop leaking when hot. worth just testing/tightening the packing gland nut on the new valves
