Water leaking from heating coil into cylinder?

[Ackoman]

Dear all,


Since we moved into our new home (built in 1971), we’ve had nothing but problems with the plumbing, at least some of them self inflicted – to try and keep this concise, I’ll list the problems in bullet point form:

1. Screw put through pipe when trying to secure some floor boards – not noticed at the time, because there was no immediate water leak
   
   
2. Later that day, boiler (Vaillant Ecotech plus 618) not providing hot water to coil in hot water cylinder
   
   
3. Inspection of boiler showed F.75 error and boiler low in pressure. It may well have been low in pressure since we moved in – we had had no reason to inspect it.
   
   
4. System was re pressurised and F.75 error went away.
   
   
5. Overnight, the pressure dropped again
   
   
6. This then made me think I had damaged a pipe when doing the floorboards, and so it turned out – screw straight through centre of pipe. Did not apparently cause a leak though – water only started to come out when screw was removed. Plumber called and new section of pipe put in to replace damage section.
   
   
7. Quite a bit of water came out during the plumbers repair, but we did our best to contain it and mop it up. The pipe appeared to be going to taps though, and not central heating, so why would a leak in that pipe cause pressure to drop?
   
   
8. He refilled the system
   
   
9. Overnight it lost pressure again and showed F.75 error again.
   
   
10. Plumber came back twice that week and replaced two (yes, two) pressure sensors in the boiler.
    
    
11. F.75 error was replaced with a F.22 error.
    
    
12. He refilled the system, and all seemed well.
    
    
13. Overnight, the pressure had dropped again though.
    
    
14. Also, overnight water had been found to have been dripping through living room ceiling, in a place several meters away from where that screw was put through a pipe. i.e. not obviously related.
    
    
15. Plumber called again – we managed to convince ourselves that the leak in the living room was in fact water from the earlier screw through pipe incident, and there were not any other leaks.
    
    
16. Plumber did notice a small leak on the PRV, which he replaced.
    
    
17. The pressure still dropped, but over a much longer period of time (3 days or so).
    
    
18. I refilled the system, and around 1 hour or so later we had water coming through the living room ceiling again.
    
    
19. System now drained and I’m not refilling it again until I’ve got a better idea of what on earth is going on.
    

Additional info:


For some reason, the filling loop to pressurise the boiler is remote from the boiler itself. The boiler is in the garage, but to pressurise it you have to open a tap which is directly connected to the heating coil in the hot water cylinder. This is a pain, because you cannot see what pressure you have got to when opening the tap. When the tap is opened, I am convinced that I can hear water mixing –i.e. not just water running through the coil, but water coming out of the coil and into the stored hot water. This would explain the pressure loss, but where would this water go?


After the kids had their bath yesterday, I noticed silt in the bottom of the bath after it had been drained. This is also making me think that the heating coil is leaking and I am getting water from the boiler and central heating system mixing in with the water in the cylinder.


Is there any easy way to test my theory that water is escaping from the heating coil and into the cylinder?



Any help would be much appreciated, as this is driving me nuts! We only moved in 4 weeks ago, and it doesn’t feel like home yet because pretty much all we have done is fix problems (and cause some).


Thanks,


Ackoman

 

[Agile]

When the tap is opened, I am convinced that I can hear water mixing –i.e. not just water running through the coil, but water coming out of the coil and into the stored hot water. This would explain the pressure loss, but where would this water go?

Thanks,


Ackoman

We keep on hearing people "think" that they can hear water mixing and going through pipes. The reality is that you cannot.

There are so many threads explaining how to diagnose water leaking from a heating coil in a cylinder. It is rare but does happen sometimes.

If it was leaking then the CH water becomes cylinder hot water and is used for bathing etc.

Tony

 

[Ackoman]

When the tap is opened, I am convinced that I can hear water mixing –i.e. not just water running through the coil, but water coming out of the coil and into the stored hot water. This would explain the pressure loss, but where would this water go?

Thanks,


Ackoman

We keep on hearing people "think" that they can hear water mixing and going through pipes. The reality is that you cannot.

There are so many threads explaining how to diagnose water leaking from a heating coil in a cylinder. It is rare but does happen sometimes.

If it was leaking then the CH water becomes cylinder hot water and is used for bathing etc.

Tony

And would explain the appearance of silt in the bath then presumably?

 

[Hugh Jaleak]

Silt in the bath could be historic crud that's collected in the cylinder. For the coil to pinhole, it would allow pressure to escape from the heating side into the DHW, but highly unlikely (unless coil has split) to allow crud through, and if there was a split the pressure would be lost immediately, not overnight. 'Silt' could even be muck from the kids hair?

Its highly unlikely, as Tony has said, you would hear water mixing inside the cylinder. This water would be leaking under pressure, very slowly, into a body of water, and any sound would be deadened by the contents of the cylinder.

Simple answer to pressure gauge situation, fit another at a suitable point adjacent to the filling loop.

You've clearly got a leak still, there is water coming through the ceiling. Its possible now the system has been topped up the additional pressure has found another weak spot in the system, and as a result has sprung a leak there. I would be looking to locate and fix this first before worrying about the cylinder.

 

[Ackoman]

. 'Silt' could even be muck from the kids hair?

.

My kids are dirty, but they are not *that* bad!

Ever since we moved in (even before in fact) I've had a notion to get the cylinder replaced with an unvented one, as I want to do away with the cold water tank in the loft and get decent pressure in all the taps. All this shenanigans is just making me more inclined to go down that path.

 

[Hugh Jaleak]

Straight away there's a possible issue, have you checked the condition of the cold storage cistern feeding the cylinder? From rotten chipboard lids to dead animals, all sorts can find its way in, and that would be the first place I look for crud. Even if its clean then there's no guarantee muck hasn't already found its way into the cylinder. The Byelaw 30 kit addresses the issue to some extent but there are still a lot of cisterns out there with no proper covering.

Unvented, provided mains supply is up to the job, is the way to go these days.

 

[Ackoman]

Straight away there's a possible issue, have you checked the condition of the cold storage cistern feeding the cylinder? From rotten chipboard lids to dead animals, all sorts can find its way in, and that would be the first place I look for crud. Even if its clean then there's no guarantee muck hasn't already found its way into the cylinder. The Byelaw 30 kit addresses the issue to some extent but there are still a lot of cisterns out there with no proper covering.

The cold water tank does have a covering. When the plumber came round to fix the damaged pipe, he did go up in the loft to double check that he had emptied the tank and he didn't say anything about the tank not being suitable or adequate.

 

[Hugh Jaleak]

Suitable or adequate would probably run so far as to it's big enough, is sitting on a suitable base, and probably has a lid on it. Most plumbers wouldn't give it a second glance unless they were investigating an issue concerning the cistern, or there was something glaringly obvious wrong with it. Some detritus in the bottom is also usually pretty common, and unless it was deep or stank, it wouldn't be an immediate cause for concern. Ultimately this water is used for washing and bathing, potable (drinking) water should always be drawn from the mains supply.

 

[Ackoman]

Suitable or adequate would probably run so far as to it's big enough, is sitting on a suitable base, and probably has a lid on it. Most plumbers wouldn't give it a second glance unless they were investigating an issue concerning the cistern, or there was something glaringly obvious wrong with it. Some detritus in the bottom is also usually pretty common, and unless it was deep or stank, it wouldn't be an immediate cause for concern. Ultimately this water is used for washing and bathing, potable (drinking) water should always be drawn from the mains supply.

Presumably I could try filling the bath with just cold water and look for silt, and then do the same again with just hot water?

 

[Hugh Jaleak]

That depends if the bathroom cold supply is mains or cistern fed. At one point in time a lot of properties were plumbed with the kitchen cold tap from the main (for drinking and cooking), all other cold supplies were taken from the cistern in the loft. Now most cold outlets are straight from the mains, unless you need a balanced supply e.g. for a mixer shower.

 

[picasso]

Get the expansion vessel checked in the boiler, its most probably flat and overpressurising your central heating system causing leaks.

 

[Ackoman]

That depends if the bathroom cold supply is mains or cistern fed. At one point in time a lot of properties were plumbed with the kitchen cold tap from the main (for drinking and cooking), all other cold supplies were taken from the cistern in the loft. Now most cold outlets are straight from the mains, unless you need a balanced supply e.g. for a mixer shower.

Don't know for sure, but based on the slow rate that it comes out of the bathroom tap I would say it was fed from the cistern in the loft. The only cold water tap in the house that has a decent pressure is the one in the kitchen.

 

[Ackoman]

Get the expansion vessel checked in the boiler, its most probably flat and overpressurising your central heating system causing leaks.

The plumber (I keep calling him a plumber, but he's a Gas Safe installer) seemed satisfied that the expansion vessel was fine - after he replaced the PRV for one which didn't leak, we pressurized the system and when the boiler was running it rose to about 2.5 bar. He said that if the expansion vessel was flat then it would go higher than that and water would start coming out of the PRV.

 

[Hugh Jaleak]

Turn the mains supply off, (check at kitchen tap it has actually turned off and isn't letting by!), then try the other cold outlets in the house. If mains fed they'll soon reduce to a trickle, then nothing, if cistern fed it wont diminish until stored water has been depleted.

 

[Ackoman]

Turn the mains supply off, (check at kitchen tap it has actually turned off and isn't letting by!), then try the other cold outlets in the house. If mains fed they'll soon reduce to a trickle, then nothing, if cistern fed it wont diminish until stored water has been depleted.

Ah yes of course, we've already done that as we emptied the cistern when he replaced that section of pipe - all the cold taps bar the one in the kitchen kept running until it was empty.