loss of hot water in cylinder ..unvented system

[derbyrib]

Hi
Last few days have noticed that after heating the water through gas boiler, if not run off the water temp drops significantly..last night from 50 down to 17 within 30 minutes...Can the system be cooling the water or is it a leak somewhere draining the hot water? My plumber is away on holiday for another week.
Thanks

 

[Riley]

Hi there obviously somethings not right but as it's an unvented cylinder you can't touch it as you need to be G3 qualified. Maybe you could try here [DLMURL="http://www.ukplumbersforums.co.uk/im-looking-plumber-gas-engineer/"]I'm looking for a Plumber or Gas Engineer[/DLMURL]. Is your heating on a sealed system? Ie no tanks in the loft at all

 

[derbyrib]

Thanks. I have no plan to touch the system myself. Just interested to know if I have to find a leak and how to do that on pipes covered in the floor screed.
Yes it is a sealed system.

 

[Riley]

Is there a tundish by your cylinder? Is it dripping or is water running through it

 

[derbyrib]

Yes there's a tundish but no water dripping

 

[Best]

Yes there's a tundish but no water dripping

But have you looked at the tundish when the water in the cylinder has just been heated fully?
If there is water dripping into tundish when the cylinder is hot, then you will need the cylinder serviced as it has a fault.
What make is the unvented cylinder?

 

[derbyrib]

Thanks for responding.The cylinder is a Stelflow. Even when the water is heated there is no water in tundish..in fact it is dusty!
I think I have proved just now that we have a leak. With no taps open I can see the water meter is still turning, and stops when I close mains stopcock. The layout is ground floor, beam and block, thick insulation, underfloor heating and 50mm screed. The pipework was put into the insulation before the screed was laid. The pipes run along floor by kitchen wall, and from outside I can hear water flow through an airbrick. So it looks like a builder I need before a plumber! Thanks again for advice.

 

[Best]

That is unfortunate! Your builder might be best to employ a plumber or someone who can first try to locate the exact area the leak is. With it being hot water it might be possible to have your unvented unit heated and then the water mains turned back on to see if thermal gear could find a hot area in the floor. Might not work due to pipes being buried with insulation, but perhaps worth a try.
Also they could try sound equipment to find the noise

 

[Radioman]

Most if not all buildings insurers will only pay for the damage a leak causes not track and trace. If the property is NHBC covered you may try that. Sounds like an invasive detection process. It may be less invasive to re plumb the hot side completely

 

[derbyrib]

Thanks
My builder has given up 2 hours of his bank holiday today, part dismantled a kitchen unit, and hacked thro 2 " screed,8" insulation, exposed the pipe and connections to the sink taps...established that we do have a leak in that area, but unfortunately not at those connectors...so tomorrow unit 2 is to be dismantled to access next most likely connection...wish we had installed pipework in channels for easy access 3 years ago, but hey! hindsight is a wonderful thing! We considered the option of replumbing hot side, but because of the configuration that would involve similar disruption, but if we don't find the problem tomorrow we may have to rethink
Thanks again

 

[Scott_D]

Any pictures of the cylinder?

 

[Best]

Any pictures of the cylinder?

Sounds now like the OP has a leak in a hot pipe in house unrelated to cylinder.