Search the forum,

Adding a second Expansion Vessel?

Discuss Adding a second Expansion Vessel? in the Plumbing Jobs | The Job-board area at PlumbersForums.net

D

Duker996

Messages
76
I was at a job looking at an unrelated issue when the lady mentioned her blow off keeps running outside. Apparently the last plumber replaced expansion vessel(and checked the precharge was 3bar) on the cold feed into the cylinder, 3bar pressure reducing valve and 6bar blow off in the hope to cure it.

The cylinder temp/pressure relief valve, htg relief valve and hw relief valve are all connected into one 22mm pipe. The cylinder valve has a tundish which isn't showing any signs of water, the htg pressure stays well below 3 bar and when disconnected shows no sign of letting by.

So it's all pointing to the kit on the mains pipe feeding the cylinder. I didn't take note but I want to say the vessel is around 24l and is positioned about 4 metres from the cylinder. Is it a case that an extra vessel may be needed as it's over pressurising?
 
The vessel supplied with unvented cylinder (or identical replacement) will be correct size for the unit and nothing else needs added.
Something else is faulty and it could also be elsewhere in the cold and hot water system in the house.
As said, don’t touch anything unless you have the unvented qualification or you could get the blame
 
At which point did I say I don't have the G3 qual? I do have the qualification and understand exactly how all the parts work. I have just never encountered this problem before so asked for advice, which I'm never too proud to do. Don't be so quick to judge chaps!

I think you may have nailed it Best, turns out the issues started after they had a new bathroom fitted so my guess now is no check valves on the feed to the new shower.
 
Duker996 said:
At which point did I say I don't have the G3 qual? I do have the qualification and understand exactly how all the parts work. I have just never encountered this problem before so asked for advice, which I'm never too proud to do. Don't be so quick to judge chaps!

I think you may have nailed it Best, turns out the issues started after they had a new bathroom fitted so my guess now is no check valves on the feed to the new shower.
Click to expand...

Maybe no balanced cold then?
 
Like Best and you say Duker I’d be suspicious of something downstream back pressurising. When I used to do site work the guys used to put one PRV under sink on incoming and then obviously the one in cylinder cupboard with balanced draw off. Some people even install pressure gauges so you can see exactly what’s going on
 
A vessel installed 4M away from the cylinder is very unlikely to be the right side of a check valve if it is on the cold feed.
Could it be there for another reason other than expansion ?
I diagram would be useful as I am struggling to understand what is going on from your description Duker996.
 
chris watkins said:
A vessel installed 4M away from the cylinder is very unlikely to be the right side of a check valve if it is on the cold feed.
Could it be there for another reason other than expansion ?
I diagram would be useful as I am struggling to understand what is going on from your description Duker996.
Click to expand...

Good point Chris, I overlooked that
 
Duker996 said:
At which point did I say I don't have the G3 qual? I do have the qualification and understand exactly how all the parts work. I have just never encountered this problem before so asked for advice, which I'm never too proud to do. Don't be so quick to judge chaps!

I think you may have nailed it Best, turns out the issues started after they had a new bathroom fitted so my guess now is no check valves on the feed to the new shower.
Click to expand...
You didn’t say that you was G3 registered either!
 
chris watkins said:
A vessel installed 4M away from the cylinder is very unlikely to be the right side of a check valve if it is on the cold feed.
Could it be there for another reason other than expansion ?
I diagram would be useful as I am struggling to understand what is going on from your description Duker996.
Click to expand...
Maybe it's a megaflo?
 
JasetheMace said:
That would be my guess! If expansion vessel is 4m away, more likely to be heating expansion vessel rather then hot water.
Click to expand...
The OP has their G3 so I would expect them to be capable of knowing the difference between heating & hot water vessels.
20190305_141608.jpg

Even if it is a Megaflo with an internal air bubble for expansion addition vessels can & are often added, for instance when the baffles has failed or there is a secondary return installed which increases the amount of water being heated.
The worry here (as far as I can tell from the description) is that it has been installed on the cold feed 4 Metres away from the cylinder so it is very likely to be on the wrong side of the check valve which is built-in just before the pressure relief safety valve. If it is then this will isolate the vessel from the source of expansion so it can't work & the pressure will continue to cause the safety valves to open!!
 
All sorted now chaps.

As Gary said it was due to not having balanced supplies at the new shower and them clearly not fitting check valves. There was no way of me getting to any of the shower pipes so a 3bar pressure reducing valve on the incoming main has cured it.

No idea why the vessel, relief valve, reducing valve etc was placed in a small roof space 4 metres away but it is all correct and how it should be, no check valve between the vessel and cylinder.

First time I've seen this issue in my 19 years plumbing, hence why I was a bit baffled by it!

Thanks all for the help
 

Reply to Adding a second Expansion Vessel? in the Plumbing Jobs | The Job-board area at PlumbersForums.net

Similar plumbing topics

johndave
Outdoor stopcock doesn't fully close
Hi all I'm hoping someone can shine a light on this for me Since our stop tap on the pavement has now been filled with sand for whatever reason, we are relying on our property fitted stopcock (this is outside on our garage wall) Unfortunately turning this to the closed position only reduces...
Replies
3
Views
174
exedon2
exedon2
P
Repeated Airlock in Bathroom
Hi, Can anyone advise as to why the cold water to my bathroom keeps airlocking? This originally happened about 12 months ago and has happened 3-4 times since. It’s an upstairs bathroom, fed from a tank in the attic. The tank is about 8 Meters away and feeds a bath, sink and toilet. The tank...
Replies
9
Views
255
Chuck
C
Creating content since 2001. Untold Media.

Newest Plumbing Threads

Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock