Replacing a hot water tank - is this reasonable?

[ianmcd]

Not sure I understand? Would changing to a standard HW cylinder not take care of that?

if you do that what is going to heat your radiators ?

 

[ianmcd]

OK, so the more I read about how a thermal store works, the more it doesn't seem to fit with the current issue we're having. Currently the main issue we have is that the we can't run a bath. After running the hot tap for about 30 seconds, the water turns cold. However we can run the showers fine. If the water is only being passed through the tank and not using water from it, how does the suggested issue of scale cause what we're experiencing?

Sorry we dont have crystal balls, you never mentioned this before, unlikely to be the thermal store more likely to be a blending valve or similar

 

[shorn]

Sorry we dont have crystal balls, you never mentioned this before, unlikely to be the thermal store more likely to be a blending valve or similar

Sorry, I realised that I never added that to the original post. We were told this was due to the tank being scaled up.

To be honest, I'm not sure what's the best way to tackle this. Is it worth replacing the blending valve? As you can see from the photos the pipework is a bit of a mess, but if it's just replaceable components that need changing, I'd rather do that then replace the entire system.

For context, we move to this house a couple of year ago and haven't started decorating anything yet. We are looking at starting this year, but I want to make sure we have the CH system sorted before we start decorating other rooms and find we need to run anything up again.

 

[ianmcd]

Agree your blending valve needs attention, it has been leaking for a long time, if your heating is working OK , then unlikely to be limescale, thermal stores are known as sludge buckets for good reason, but if the HW is ok at some outlets and not others it is unlikely to be the thermal store, as a side note your gas boiler must be set at max for the thermal store to work properly

 

[Harry Bloomfield]

Bumping in the hope anyone has any further thoughts.

Not suggesting this as the solution, just wondering if it might work as a solution.....

Citric acid is quite cheap and will dissolve limescale, without damaging the metal. It comes as a powder, in packets, to mix with water. Pour it in, leave it a couple of days, then flush out. It would require several packets. Wilko sell it. I use it regularly on taps, shower heads etc..

 

[shorn]

I think that's worth changing the blending valve as a first step. Seems to make sense and now I look at it, looks obviously that is what's leaking. From looking at it seems a simple replacement. Three compression fittings right? or am I misinterpreting it (always a possibility )

 

[shorn]

Screenshot 2021-02-18 At 10.44.59

• shorn
• 18 Feb 2021

Just had a look at the blending valve, and starting to understand it a bit better. So I've marked where the cold feed comes in. This comes up and mixes with the hot water that's coming out at the valve.

Just tested and ran the bath taps for a minute or so. When I put my hand around the HW out after the valve, this starts hot, but in 30 secs or so starts to cool down. When I stop the tap and run the shower (above the same bath) the pipe (in the same place gets hot again). Dodgy valve? I can't understand why calling it from another outlet makes a difference?

Anyhow, if I was to look at replacing, from what I can gather, I 'd need to turn off the main cold in, (there's a tap just before the limescale filter.) Then run the hot for a bit to drop the level in pipes. Should be OK then to remove/replace the valve?

 

[Laurieo]

Is it only one tap in the house that goes cold ?.

 

[shorn]

Is it only one tap in the house that goes cold ?.

It just seems to be the bath taps.

 

[Laurieo]

Is it a mixer or thermostatic tap
I would be looking at tap before changing heat store.

 

[shorn]

Straightforward mixer. Agree that would be worth checking, but then that doesn't explain the fact that the HW pipe, just after the blending valve, gets cold after running the bath tap for a minute.

 

[Laurieo]

If the mixer is stopping the hot water flowing then there will be no call for hot water from tank so pipe will go cold .
Can you run shower and bath tap at same time ?
If so is tap water hot ?.

 

[shorn]

Running them both together at the same time, they both start hot and shortly after they both go cold. Switching the bath off then and leaving the shower running, the shower starts to heat up again.

 

[Agile]

I am also dubious about this apparent diagnosis of scaled up.

But thermal stores so have a bad reputation as sludge buckets.

To treat them with chemicals is expensive and hardly anyone ever seems to bother.

I still do not see how that quote can be very reasonable.

I would be considering an unvented cylinder which would be about £950 fitted at my prices. But that would need a good mains water dynamic flow and pressure.

 

[shorn]

I would be considering an unvented cylinder which would be about £950 fitted at my prices. But that would need a good mains water dynamic flow and pressure.

That seems more like the prices I would have expected.

The other option for us is to rip the whole lot out and replace with a combi. That's what a lot of the engineers that have visited have recommended (although their possible failure to diagnose our current issue correctly leaves me unsure).

If we were to replace with a combi, we'd be looking at relocating the boiler to the airing cupboard, which is the opposite side of the house to the existing one. As I don't want the pipework running on the outside of the house, we bee looking at taking up flooring and boxing in, hence I want to make that decision now, before we embark on decorating any rooms.

I've never had a combi, only HW tanks, so although I know they are commonplace, it's still unfamiliar to me.