Problem with duel coil cylinder... i think?

bbam

Hi folks..
I'll try and explain my problem withoug going on to next friday...

Started having problem with overflow from small tank from heating system running a good bit..
Checked Ball-cock and it was dribbling a bit so I tied it back and removed some water from the tank to check..
Two days later the overflow was going again, tank overfull... steady trickle :mad:

With the ballcock closed there is no water feeding the system into the tank..

I've a good understanding of the plumbing as we build the house ourselves 12 years ago...

I'm thinking that the heating coil in the cylinder must be leaking, allowing water from the DHW side into the heating loop and filling it up..

Has anyone seen this? Or am I overlooking something else??

Presuming its the cylinder...
If I buy a replacment duel-coil cylinder can I expect the connections to align for a straight swap or would thei require re-plumbing to fit ??

Any help appreciated...

bam.

ART6

bbam wrote: »

Hi folks..
I'll try and explain my problem withoug going on to next friday...

Started having problem with overflow from small tank from heating system running a good bit..
Checked Ball-cock and it was dribbling a bit so I tied it back and removed some water from the tank to check..
Two days later the overflow was going again, tank overfull... steady trickle :mad:

With the ballcock closed there is no water feeding the system into the tank..

I've a good understanding of the plumbing as we build the house ourselves 12 years ago...

I'm thinking that the heating coil in the cylinder must be leaking, allowing water from the DHW side into the heating loop and filling it up..

Has anyone seen this? Or am I overlooking something else??

Presuming its the cylinder...
If I buy a replacment duel-coil cylinder can I expect the connections to align for a straight swap or would thei require re-plumbing to fit ??

Any help appreciated...

bam.

Certainly sounds like water is crossing from one system to the other alright, and if it is I can't think of any other reason than a leaking coil. However, question: Is the heating system header tank maounted at a lower or higher level than the main water tank? If it's higher, or if the water level in it is at the same height as that in the main tank, then water from the hot water system can't cross over. If it's lower then it can.

Next question: Is your heating system atmospheric or pressurised? If the latter then the cross over would be the other way.

If the heating system is atmospheric, is it possible that the vent pipe from the hot water system is simply going to the wrong tank? Sounds silly I know, but it has happened;)

I couldn't be sure about the fit between a new and an old dual coil tank, but I would expect them to be the same.

bbam

Interesting...
Heating header tank is marginally higher...
Neither system are pressurised...
Vent pipes are right, problem started recently with no changes to system.
Isnt the highest point in the DHW system the vent pipe when its heated? This would create pressure difference enough to fill heating loop ??

Its a pain cos the dirty water is staining outside and house is for sale.. :mad:

PlumbNHeat

Tie up the ball valve in the large domestic water tank turn on one hot tap and let all the water drain from the tank ,if the water stops flowing from the tap
your cylinder coil is ok. If theres a little flow (trickle) of water and the small tank in the attic is feeding the central heating system its the coil leaking.
Its rare that a coil leaks but does happen,
The cylinder is not that old. be sure it is the coil before ya change it for a new one .

Hope this helps

bbam

Thanks PlumbNHeat...
I'll try that when I get a chance...

Avns1s

bbam wrote: »

Interesting...
Heating header tank is marginally higher...

It's the height of the surface level of the water in the tanks that is important.

If the surface level of the water in the header tank for the heating is higher than the Hot and Cold water tank then the increase in the level cannot be coming from the coil. The opposite is also true.

Is it possible that the ballvalve is still leaking some water into the tank even though it's tied up. That's where I'd be looking to be honest. While it's not impossible, it is unusual that the coil would leak like that, particularly in a cylinder that it 12 years old unless of course, you live in a very hard water area. Even then, in my experience, it's more likely that the cylinder itself would leak rather than the coil.

Finally, a direct swap for a new cylinder without the need for some replumbing, would be very unlikely. The connections would be in slightly different places. A couple of mm up or down will make a direct swop impossible.

bbam

Ballvalve definitely not leaking at all... have checked repeatedly when overflow going..

311

bbam wrote: »

Ballvalve definitely not leaking at all... have checked repeatedly when overflow going..

If your coil was leaking ,your hot water would be a bit dirty. Try running your hot tap for about a minute ,then fill a white bowl with the water. See if there is any colour to the water.

bbam

bbam wrote: »

Ballvalve definitely not leaking at all... have checked repeatedly when overflow going..

I was wrong ... Found that ballcock was leaking and running down the back of the tank with no noise, only noticed when I brought a flashlamp with me, was shadowed from main light in attic..

Changed the ballcock and all has been good since...

Thanks for help folks...

Avns1s

bbam wrote: »

I was wrong ... Found that ballcock was leaking and running down the back of the tank with no noise, only noticed when I brought a flashlamp with me, was shadowed from main light in attic..

Changed the ballcock and all has been good since...

Thanks for help folks...

I won't say "I told u so"

Anyway, glad u got sorted.

bbam

Avns1s wrote: »

I won't say "I told u so"

Well you did really.... thats why I went back armed with flashlamp..

Thanks a mil