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have a feeling it’s something to do with regulating pressure in the system - it’s connected to the cold supply to the HW cylinder. I also think it should be inflated to 1 bar.
Neither of those is much more than a guess! Any help?
Sorry struggling to even use the forum on my phone never mind figure out how to embed images! Bloody pop ups…
Expansion vessel - as you say, pressurised to 1 bar, helps keep system pressure regulated when water expands and contracts with rises and falls in temperature.
Cheers - will get the track pump out in the morning!
Err, are you sure it isnt the water that needs filling, rather than the bladder of the expansion vessel needs pumping up?
Dont add air pressure to the vessel without testing it. They are quite reliable generally, but some do develop leaks, pumping them up gives a temporary reprieve, but they soon lose pressure again if the bladdr is damaged.
I have one in my system, it should be connected with hoses and valves to open to allow to refill the water to the correct pressure
Not sure how I'd add water to the vessel as the only supply to it is open all the time (I think - but no isolation valve immediately next to the vessel). I've just checked the first step of the test video above and pushed in the valve and nothing came out - no air, no water. I tried to put a track pump onto the valve to put a bit of air in to see what happened and I think the valve is knackered. I can't even pump anything into it. Might need a new vessel at some point but park it in the "one for another day" category for now!!
When you've heated up the HW tank, go and have a look outside to see if any pressure relief pipes are dribbling. That would be a sign that the vessel is borked or needs pumping up at least. You could always just grab a schrader valve core removal tool and stick a new one in.
I don't see any dribbling outside so I'm going to work on the basis of "if it's not broke..." I'm at the very limit of my plumbing knowledge and it's a pressurised system so potential for me to cock it all up.
Thanks for the advice 🙂
If you notice "water hammer" as the HW has filled then that's an indicator that all is not well
It's an expansion vessel. Water can only go one way through the pressure-reduction valve into the cylinder, so as it gets hot and expands the expansion vessel has a balloon in it to take up the slack.
To check this you can close the cold supply to the cylinder and open a hot tap to let the pressure out of the system. On the expansion vessel there's a shrader valve - if you prod the core you'll know straight away if it's failed or not because a bit of water will come out.
If it seems OK, pump it up to 1 bar and stick the cap back on. Open the cold water feed to the cylinder, turn off the tap once it stops sputtering, and you're all done.
ignore the above regarding fill pressures of 1bar - thats a nonesense. theres only one correct fill pressure and thats the same pressure as indicated on the pressure reducing valve. theres no need to 'add water' as it is live to your hot water cylinder. I'm the techie guy for a manufacturer of unvented cylinders.
if you wanted to check (and it'll be a ball ache as your vessel is mounted upside down) you should..
- turn off the cold mains supply to the cylinder.
- open a hot tap on the same floor as the cylinder and wait for the water to stop flowing.
- unscrew the black cap at the bottom of your vessel and put a schrader gauge on the valve. check the pressure. if it is less than that on the PRV then pump it up. If higher, release some pressure.
- close the hot tap, open the cold mains then repopen the same tap to get rid of any airlocks.
if the safety valves arent dripping when the unit is heating up, then the chances are the pressure is fine.