Varem shock arrestor/expansion vessel

[darren6645]

I have a Varem 0.16l mini expansion vessel/shock arrestor on the cold water inlet side to my thermal store. This cold water supply feeds the coil in my tank then exits the tank via a blender valve to give me mains pressure hot water at the preset blender valve temp. I've recently started to get some water hammer when things close off quickly, there is no pressure in this vessel at all. I have tried pressuring it up with a pump but I suspect the membrane has failed.
I'm going to replace it but I'm struggling to find one with the same spec. Current one is preloaded to 5 bar I only seem to be able to find a replacement that states preload 3.5 bar, everything else appears to be the same values, will this be ok?

Two of the images are of existing vessel but very difficult to get a picture, other is replacements that keep coming up when searched.

 

[Johntheo5]

If the membrane has failed then when you press the pin in, in the schrader valve, water should come out, if no water or air then shut off the cold mains to the HW coil and open a hot tap to depressurize the system, then pump it up, I would think 3.0bar might be a more appropriate pressure especially if you have a PRV on the cold water supply which would generally be set to 3.0bar.

 

[ianmcd]

you need to turn off the cold supply and leave a hot tap open , once the water stops running then you pressurise the vessel, with the tap still open, if you dont do all that no point in doing anything , wont take much pumping up when done correctly

 

[darren6645]

I'll check again for water from schrader valve but I definitely did as above (cold off, hot open) when I tried to pressure it up.
Thanks.

 

[Johntheo5]

Sometimes the diaphragm can get jammed hard up against the end of the EV and nothing will shift it or maybe you are saying that you can pump and pump but no pressure rise?, if so then water should defititely come out when you press in the pin with the coil pressurized.

 

[darren6645]

Thanks again Johntheo5 that makes sense. I will investigate further when I'm home tomorrow and let you know how I get on.
Much appreciated

 

[darren6645]

Sometimes the diaphragm can get jammed hard up against the end of the EV and nothing will shift it or maybe you are saying that you can pump and pump but no pressure rise?, if so then water should defititely come out when you press in the pin with the coil pressurized.

I've pressed the pin with the water still on and no water or air came out. I had previously pressured it up as above a few weeks ago so seems to have lost pressure but not passing water?

 

[Johntheo5]

Assuming you still can't repressurize it with cold supply off and a hot tap remaining open then remove it, shut the hot tap and crack open the cold supply to get a small trickle through the now open pipe, if pipe proven clear then get a new shock arrestor.

 

[darren6645]

I pressured it up on the pump gauge to 3bar last time but when the pin was pressed today no air. Cold supply is 100% clear as everything is working fine in that respect. I'll give it another try in the morning

 

[Johntheo5]

I pressured it up on the pump gauge to 3bar last time but when the pin was pressed today no air. Cold supply is 100% clear as everything is working fine in that respect. I'll give it another try in the morning

If you can pressurize it to 3.0bar with mains off/HW tap open and you loose that pressure very rapidly it must be leaking out through or around the schrader valve, you could try a new schrader valve insert, if this doesnt work then a new shock arrestor required IMO.

 

[darren6645]

If you can pressurize it to 3.0bar with mains off/HW tap open and you loose that pressure very rapidly it must be leaking out through or around the schrader valve, you could try a new schrader valve insert, if this doesnt work then a new shock arrestor required IMO.

Hi mate. I've done as above and soapy bubbled the schrader valve, it's defo passing so I've fitted a whole new E/V
I appreciate your help and advice thanks for your quick replies and assistance