I suspect that there has been some kind of failure with the expansion vessel on my unvented hot water cylinder.
A couple of times a day, hot water spouts from the overflow, maybe a litre or two. The system is about 18 months old and this probably started 6 months ago.
I've tried poking the valve on the back of the expansion vessel (blue one) and there's nothing coming out, not gas or water. I've also tried sticking a tyre pressure gauge, but it just doesn't get a reading. (When I check the heating circuit expansion tank this reads exactly the same as the attached gauge, so that's all fine).
I've read about water coming out of the valve when the diaphragm in the expansion vessel fails, but my symptoms appear to suggest that the valve itself is leaking gas, so the vessel has effectively no pressure on the gas side, and therefore no expansion capability.
Does anyone agree with my diagnosis? Is this common? What can I do to test this theory further before I call the appropriately qualified person to change the vessel?
Thanks.
Matt
A couple of times a day, hot water spouts from the overflow, maybe a litre or two. The system is about 18 months old and this probably started 6 months ago.
I've tried poking the valve on the back of the expansion vessel (blue one) and there's nothing coming out, not gas or water. I've also tried sticking a tyre pressure gauge, but it just doesn't get a reading. (When I check the heating circuit expansion tank this reads exactly the same as the attached gauge, so that's all fine).
I've read about water coming out of the valve when the diaphragm in the expansion vessel fails, but my symptoms appear to suggest that the valve itself is leaking gas, so the vessel has effectively no pressure on the gas side, and therefore no expansion capability.
Does anyone agree with my diagnosis? Is this common? What can I do to test this theory further before I call the appropriately qualified person to change the vessel?
Thanks.
Matt
