Hot Water Running Out

[dilalio]

Sorry, I'm very much an amateur here, I'll try get my plumber around next week to do this but can you put this in idiot terms for me and tell me what that is and how to check it?!

Probably need your plumber (make sure he is G3 certified if working on the UV cylinder).

You need to be able to isolate the hot supply to the system and then see if water continues to run from a hot tap after 10 mins or so.

This would indicate that a NRV in a thermostatic mixer has failed and cold water is crossing over and flowing down the hot pipe which can cause blending of hot and cold at other outlets, thus giving you tepid or cold water, if the pressure difference is great enough.

 

[valleycushion]

Probably need your plumber (make sure he is G3 certified if working on the UV cylinder).

You need to be able to isolate the hot supply to the system and then see if water continues to run from a hot tap after 10 mins or so.

This would indicate that a NRV in a thermostatic mixer has failed and cold water is crossing over and flowing down the hot pipe which can cause blending of hot and cold at other outlets, thus giving you tepid or cold water, if the pressure difference is great enough.

Thank you, I think thermostatic valve you're talking about is this one in the silver box at the bottom - is that right? If so a plumber checked that a few weeks ago when we had our boiler and water cylinder annual service and he seemed to think it was doing what it should be (opening and closing?)

 

[dilalio]

Nope. That's a motorised 2 port valve.
I'm referring to mixer taps in your bathrooms.

 

[valleycushion]

Nope. That's a motorised 2 port valve.
I'm referring to mixer taps in your bathrooms.

Ha! Thank you, told you I was a novice! Will try that - should I do it on all mixer taps (and the showers) in the house?

 

[dilalio]

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[Johntheo5]

Thank you. In laymans terms, what does this mean? We have two kids and two adults. The kids shower every other day (short showers) on an evening, the adults shower in the morning, again pretty short.

Whatever shower(s) you are using, run them at your normal showering rate, get a bucket/container and hold it under the shower head in its normal (holder) position for exactly 30 seconds (to the second), measure this with a 1 litre container, X2 to give you the shower flowrate in LPM, this will give a very good idea of the shower consumption then, based on time under the shower(s),

 

[dilalio]

Whatever shower(s) you are using, run them at your normal showering rate, get a bucket/container and hold it under the shower head in its normal (holder) position for exactly 30 seconds (to the second), measure this with a 1 litre container, X2 to give you the shower flowrate in LPM, this will give a very good idea of the shower consumption then, based on time under the shower(s),

This is a new issue that hasn't been a problem in the past if I've read the thread properly?

 

[Daveydub]

Run a shower on hot till the body is nice and hot.
Turn off shower and open a cold tap.
Cold running through shower valve will rapidly cool the shower body.

The faulty valve could well be providing a secondary loop, circulating on gravity, which would deplete the hot water store.

 

[valleycushion]

Run a shower on hot till the body is nice and hot.
Turn off shower and open a cold tap.
Cold running through shower valve will rapidly cool the shower body.

The faulty valve could well be providing a secondary loop, circulating on gravity, which would deplete the hot water store.

Thanks, just to confirm this. What do you mean by shower body? Is that the pipe that goes from the taps to the shower head. If so that is being the tiles in our shower.the rainfall head comes out of the wall on a long pipe.

Could this also be a bathroom mixer tap. The one on our sink was leaking cold water out of it when it was turned off a while ago, it’s intermittent and would always stop if you did a bit of a hot first.

 

[JohnD]

feel round the cylinder for a pipe that is hot and a pipe that is warm, even when neither taps nor boiler is running. That will be where the heat is going.

 

[valleycushion]

feel round the cylinder for a pipe that is hot and a pipe that is warm, even when neither taps nor boiler is running. That will be where the heat is going.

The hot water and heating have been off for a few hours now. I just ran a tap and got hot water from it, I have hot, warm and cold pipes - is that how it should be?

 

[valleycushion]

Update for those who care. In my experimenting, I just put the hot water on always on for two hours. It ran for 90 mins this morning till 730am. When I got home at midday there was still hot water coming from the tap. I put the system on, just checked it now and the boiler has been running non stop during that time and the hot water out of the tap is super, super hot. Does that help point towards anything?

 

[JohnD]

the hot water out of the tap is super, super hot.

Have you got a thermometer?

 

[JohnD]

The hot water and heating have been off for a few hours now. I just ran a tap and got hot water from it, I have hot, warm and cold pipes - is that how it should be?

You have to feel them when you have not run a tap or the boiler for at least an hour. They should then all be about room temperature.

 

[valleycushion]

You have to feel them when you have not run a tap or the boiler for at least an hour. They should then all be about room temperature.

Boiler and hot water went off about an hour ago and the pipes that were cold earlier are still cold, the pipes that were very hot now feel lukewarm 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.

Having done that I then stuck a thermometer under the hot tap and its 56C