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Discuss Serious and pre-existing leak or thermal store error? in the Plumbing Jobs | The Job-board area at PlumbersForums.net

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Now sorted... don’t bother reading this stupid long post.


Hi,

I’ve got a bit of a head scratcher here and wondered what you guys would make of it.

I was called by a landlord to do a gas safety check on a property that is now at the latter stages of being sold and the buyers wanted the usual gas & electrical certificates. It’s a 4 bed property with 2 bathrooms that I’ve been doing the gas safety checks on for about 5 years. The hot water and heating is supplied by a Baxi Solo 3 PFL and a Manco Powerstream thermal store.

The property hasn’t been inhabited for about 9 months I think he’d said and I hadn’t been there for a couple of years. Anyway, I turned on the demand for heating and hot water and went to look at the fire and the cooker knowing that the fire needed servicing. After 20 minutes or so I went to check the rads as I’d expected a bit of warmth in them. They were still cold, no notable heat rise at all, so I went upstairs towards the cylinder checking each rad for heat and getting nothing. On getting to the 2nd floor where the thermal store is I heard unmistakable and worrying groans from the cylinder store cupboard.... opened the door to see a large crack suddenly appear in the insulation and the thing sounding like it’s about to burst. I ran down to the boiler opening a couple of hot taps on the way and turned off the boiler, gas and electric in panic at the thought of what might happen. The water was surprisingly hot and stayed so for a while given the boiler had only been running for 20 minutes or so.

So we’re slowly getting to the point of this post... but maybe not yet... I called the letting agent and say that I’m not going to reinstate the cylinder after what Ive just seen and heard and as the system hasn’t been run for a long time I’m suspecting a blockage in the feed & expansion connections. (Its a combination thermal store)

As for the rads not getting hot, maybe the pump wasn’t turning or something, I wasn’t about to kick it all back up and find out. As the sale of the house is just waiting on the paperwork and the owner doesn’t want to wait a week for a replacement thermal store to come into stock he decides he wants a combi fitted sharpish against advice that it won’t supply the main bathroom and en-suite simultaneously.

So finally we get to the crux of the matter. Yesterday we fitted a Main Eco 30kW combi, connections done at the cylinder end etc. and turn it on and as soon as the power is on, it’s lighting and firing for hot water demand. I’ve already opened and closed all the taps and released air from the system so I assume I’ve left a tap open and go looking. No sign of anything open so I returned to the boiler and it’s still on hot water demand and the hot water pipework is hot and flowing. I isolated the cold water supply at the boiler and fired the central heating and it worked fine, as expected. I then opened the cold water inlet valve and it’s calling for heat instantly so I leave it flowing now expecting to see a leak on one of our joints that I’d missed first time round. No sign of anything untoward so we leave it running and start running round the house looking for leaks, wet patches or water dripping from light fittings but there’s nothing at all to show. The toilets aren’t filling and overflowing with hot water, the outside tap isn’t running, there’s no washing machines or dishwashers connected, but there’s water flowing somewhere and there’s no sign in the property.

So there’s a few things to add now, having got home last night and having thought about it.

When I was dumping heat from the cylinder the nearest hot tap was in the en-suite on the second floor, the same floor as the cylinder. The flow was surprisingly poor.

There’s a pressure reducing valve on the mains supply just above the stop tap which is set at 2 bar and shows a drop in pressure when the boiler’s cold water inlet valve is opened and we also see the water meter showing a flow.

The previous tenants that I’ve dealt with at the property, one of whom I still go to annually to service their boiler in their own home, both left the property having found it too expensive to heat and each of them claiming to be paying in the region of £300/month for gas & electricity and about £65/month for water and only two occupants during each tenancy (yes, a four bed house). Bear in mind, this house is relatively new, circa 2003 and has good insulation throughout including Kingspan in the wall cavity and between the stud work around the thermal store etc. so it should be very efficient and therefore cheap to heat. They have never been satisfied with the flow rate in the en-suite which is on the 2nd floor but the main bathroom and kitchen are fine.

The speedfit fittings that have been fitted during the building of the house had not been tightened at all and do not seem to have any inserts in them and the soldered joints are really poor... lots of long drips of solder... so all suggesting that whoever installed it wasn’t on top of their game.


So the question, the reason for this post... is there a considerable leak somewhere on the hot water pipework that isn’t apparent in the house that may have been going on for years or have I missed something when disconnecting the thermal store and there’s some sort of device that dumps excess hot water somewhere like the waste pipework? The soil pipe from the toilets and bathroom wastes etc. are all internal and behind plastered or tiled plaster board so there’s no way of knowing if that’s where the hot water is flowing to and at the cylinder I simply capped of the hot and the cold pipework below where the cylinder used to be as the hot/cold pipework was already in the garage near the boiler for the new connections.

Thanks for reading, hope you can help.
 
Last edited:
First thing I’d do is, disconnect the hot from the boiler and pressure test that circuit with all taps closed, not to much pressure. If it doesn’t build up, you know you have a leak
 
You could have a leak under the ground floor insulation, just enough flow to fire the boiler up. Has the property a water meter, to determine how fast the leak is?
 
Seeming the plumbing is a mess, they couldn't have fitted a remote blow off on the HW pipework somewhere? If you're loosing so much water i'd expect it to show somewhere, even if it was in the slab.
 
Found it... sort of.

We’d connected to the hot water supply for a washing machine in the garage and opened an iso valve under the sink that had cut it off after some builders buggered the pipework to the garage a few years ago. I shut it off and the pressure was stable so I’ll cap it properly now. I figured it would be something daft but at 6pm on a Friday I couldn’t see it for what it was. Sorry if you’ve wasted your time reading this long post. :eek:

Now to rip up some boards for a different path.
 

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