External expansion vessels.

[TheGasMan26]

Today my I reported a ruptured diaphragm on an external exp. vessel attached to an unvented newark cylinder as water would squirt out the schraeder(air inlet valve) valve which I thought was pretty conclusive, but 1 of our older installation guys reccons this can hapoen without the diaphragm rupturing(im aware a tiny bit of water sometimes comes out innitially due to condensation inside or summat, but only a tiny amount & only wen u 1st depress the schraeder valve pin), I can't see how, can anyone confirm this?

Also while I'm here when fitting an external expansion vessel to the ch system cos the boile vessel is to hard to remove is it adequate just to screw down the dust cap of the schraeder valve the old Vessel?
All answers appreciated.

 

[davebgas]

Yes you can leave the old expansion vessel in situ providing its not leaking. Most Man-Insts will tell you so.
Just make sure the dust cap is on tight.

Dave

 

[TheGasMan26]

Yes you can leave the old expansion vessel in situ providing its not leaking. Most Man-Insts will tell you so.
Just make sure the dust cap is on tight.

Dave

Thanks, iv seen that u can leave vessel in place in MI's but never wether or not its connection has to be isolated.

Still its the 1st point I'm stuck on as I cannot see how water can get to the valve through the membrane as our install guy says.

 

[davebgas]

It should be a sealed chamber on the air side of the membrane, the diaphragm is 99% likely to be shot.. Does it squirt out when you press the schraeder valve in?

Dave

 

[TheGasMan26]

yes it is, iv encountered quite a few & as u say logic dictates the membrane must be shot, its just like I said 1 of our install blokes is bangin on saying water squirting out doesn't necessarily mean its fooked, which obviously does, especially combined with signs of discharge.

 

[davebgas]

With signs of discharge!!!!??? Its defo fooked.
Me thinks you want to take it out and show it to the old badger and ask him explain how water has magically appeared on the other side of the membrane

 

[screech]

you can get some water squirt out even if the diaphragm/membrane is ok - the old chap was spot on - to make sure you have to see how much water comes out, anymore than a cup and the diaphragm will be shot. i've seen people fit external expansion vessels even though the original one is fine, they had a tiny bit of water come out so went to the extra hassle of fitting an external one rather than repressurising the original.

it seems people are doing work that is totally unnecessary and there's plenty of expansion vessels out there that are ok but have an external one doing their job instead

 

[TheGasMan26]

you can get some water squirt out even if the diaphragm/membrane is ok - the old chap was spot on - to make sure you have to see how much water comes out, anymore than a cup and the diaphragm will be shot. i've seen people fit external expansion vessels even though the original one is fine, they had a tiny bit of water come out so went to the extra hassle of fitting an external one rather than repressurising the original.

it seems people are doing work that is totally unnecessary and there's plenty of expansion vessels out there that are ok but have an external one doing their job instead

Intresting, thanks a lot screech but how does this happen, I can't get my head round it.
And like u said the company I work for has been fitting a lot of externals, how does the water get through the membrane? Vokera tech even told me water squirtin out could only mean one thing, I'm not questioning u I just like to understand these things.

Now I just drain & charge(with PRV held open) then wait a few minutes & re-test precharge level(PRV help open all the while) to see if pressures escaping, I even LDF tne schrader valve, just can't get my head round how waters getting through membrane.