Hot Water Running Out

[JohnD]

...but the pipe which goes from the top of the water cylinder, and into a pipe that runs up into the ceiling and down into the floor feels quite hot still....

That is the pipe that supplies hot water to the taps. It is bound to be hot if you have just run a hot tap.

You need to know if it (and all the other pipes) drops down to room temperature when it has not been recently used.

If not, hot water is flowing through it, which is why your cylinder goes cold.

 

[valleycushion]

That is the pipe that supplies hot water to the taps. It is bound to be hot if you have just run a hot tap.

You need to know if it (and all the other pipes) drops down to room temperature when it has not been recently used.

If not, hot water is flowing through it, which is why your cylinder goes cold.

Yes they do - as in they go to room temp

 

[JohnD]

And none of them get colder?

 

[valleycushion]

And none of them are colder?

The cold supply ones are colder, but the ones that get hot go back to room temp

 

[JohnD]

The cold supply ones are colder

Even when you have not been running a tap? They should also come to room temperature if no water is flowing.

 

[valleycushion]

Even when you have not been running a tap? They should also come to room temperature if no water is flowing.

I think it’s the cold inlet ones which are cold. So from the mains into the tank

 

[Daveydub]

What do you mean by shower body? Is that the pipe that goes from the taps to the shower head.

No, the pipe to shower head is irrelevant.
No idea what showers you have, ideally it would be a bar shower mixer but it could be fully concealed with only push buttons available or an electronic one below bath.
You may also have blending valves (tmv) fitted to wash basins or bath and a fault with one of these would be the same as a faulty shower valve.
You may also have a thermostatic bath filler/shower mixer.
What I think is happening is that you have a failed check valve in one of your thermostats, this allows hot water to rise from the cylinder by gravity and pass through the valve into the cold which then returns to the base of the cylinder via the pipe which tees in between the control group (with the black knob on it) and the point where it enters the cylinder (with a drain off on it)

 

[JohnD]

I think it’s the cold inlet ones which are cold. So from the mains into the tank

If you are not using hot water, no cold water from the mains would be flowing into the cylinder, so the supply pipe would equalise to room temperature.

If cold water is going in, hot water must be coming out. This is why you have to feel the pipes after a period of zero use.

 

[dilalio]

Get your plumber to check because, as you're not sure what you're doing, we can't rely on the info. No offense.

 

[valleycushion]

Thanks for everyone's help here. I've had our plumber round once again and he's checked everything and it's all doing what it should be. There was a question as to whether there was a slight issue with one of the 2 port valves, so we changed that just in case.

However we still have problems.

For example last night we stayed away, but the hot water was still on between 6am and 7pm. So no one used it or showered. When I went to wash up at 2pm I had a small amount of hot water but then it was cold. I'm not being stupid here am I? We should still have hot water if it heated it for an hour and none was used?

Everything is serviced every year, and only 13 years old, it is all operating as expected. No leaks, nothing different from last year, yet we have a huge amount of variation in the gas usage.

Looking at my usage from last year the hour of heating the hot water in the morning used an average of 11kwh, this year it's an average of 20kwh, so nearly double, for the exact same usage.

Other than getting a second opinion from another plumber / heating engineer does anyone have any idea what it could be?

 

[dilalio]

Thanks for everyone's help here. I've had our plumber round once again and he's checked everything and it's all doing what it should be. There was a question as to whether there was a slight issue with one of the 2 port valves, so we changed that just in case.

However we still have problems.

For example last night we stayed away, but the hot water was still on between 6am and 7pm. So no one used it or showered. When I went to wash up at 2pm I had a small amount of hot water but then it was cold. I'm not being stupid here am I? We should still have hot water if it heated it for an hour and none was used?

Everything is serviced every year, and only 13 years old, it is all operating as expected. No leaks, nothing different from last year, yet we have a huge amount of variation in the gas usage.

Looking at my usage from last year the hour of heating the hot water in the morning used an average of 11kwh, this year it's an average of 20kwh, so nearly double, for the exact same usage.

Other than getting a second opinion from another plumber / heating engineer does anyone have any idea what it could be?

Scaled up cylinder perhaps?

I'd need to be there really.
Can't do this at distance!

 

[Murdochcat]

Set the hot water timing so it doesn’t over lap with the central heating

 

[Johntheo5]

Ring your plumber and ask him does your cylinder have a pump with secondary return.
You also stated your usage is exactly the same as last year. I would certainly do that shower flow test that I suggested, try and get a handle on what normal means.

 

[trojanhawrs]

Run a cold tap and leave it running. Go around your other sinks and check the pipework, are any of them getting hot? Feel the shower valve as well, is it getting hot?

 

[valleycushion]

Scaled up cylinder perhaps?

I'd need to be there really.
Can't do this at distance!

Haha! Are you anywhere near Bristol?