Very hot water at taps

Joined
12 Jul 2020
Messages
12
Reaction score
2
Country
Ireland
Hello good people,

I’m after some advice please. My hot water seems too hot at my taps. I have replaced my cylinder thermostat on the cylinder with a Honeywell, and it makes good contact with the metal underneath, but it still seems far too hot. It set at 60 degrees Celsius. Could it be the boiler thermostat?

Thanks for anyone’s time

Jack
 
Sponsored Links
The boiler thermostat only controls the temperature of the water leaving the boiler. This water circulates around a coil inside the cylinder and heats up the water inside it. However, once the hot water cylinder is at the set temperature, the cylinder thermostat (usually in conjunction with a motorised valve) should shut down the heating process.

Even if the boiler thermostat were faulty and was actually boiling the water, once the cylinder reached the set temperature the supply of water to it from the boiler would be switched off, and so the cylinder wouldn't get any hotter than the temperature set on the cylinder thermostat; it would just get there more quickly.

However, heating hot water in a cylinder is not an exact science. There will be a big difference between the temperature at the top of the cylinder and the bottom. Situating the hot water cylinder thermostat about one third of the way up from the bottom is usually the best place to get an average reading. But expect it to fluctuate.

If you were to remove the cylinder thermostat, and touch the metal underneath you will probably find it's not actually all that warm and not 60 degrees. It will be much hotter at the outlet pipe at the top that supplies the taps, and the thermostat will have been calibrated to take that into account, but as cylinders vary in size and shape and the cold water inlet temperature coming in may vary, all of this will have an effect on the final hot water temperature.

If the water really is too hot try turning the cylinder thermostat down, if it's still overheating then, there is a problem somewhere, but it won't be the boiler thermostat.
 
Wow, detailed and quick - I love it, thanks!

It makes sense, that something should stop the heating of the water instead of the boiler. The current cylinder thermostat is fixed at approx 1/3 - from bottom of the tank. I did try to lower it, but still feels too hot, my kids are saying it’s burning their skin. Would I be better measuring the temperature with a thermometer? (Just googled motorised valve as well - I have x2 of them that I can see).

Edit: if it’s not the boiler thermostat or the cylinder thermostat, what else could it be?
 
Last edited:
Sponsored Links
Yes I do have an immersion heater, but it’s turned off. Thank you for reading and replying
Double check that it is definately turned off, you would be surprised how many people tell us they are off, then when we attend they are on and the thermostat in them has failed
 
Double check that it is definately turned off, you would be surprised how many people tell us they are off, then when we attend they are on and the thermostat in them has failed

How do I check it’s off? It’s off on the switch. Could it be wired wrong?
 
How do I check it’s off? It’s off on the switch. Could it be wired wrong?
No if it is definately off at the switch it will be fine, so many when the Mrs is cleaning or something they mistakenly switch them on, had that exact scenario last week and the thermostat was gone, cylinder was banging when I attended, but of course no one turned the immersion on
 
Has the Temp recently increased ? or has it always been hot, the temp of the HW can never be hotter than the temp of the water leaving the boiler, and as already advised you have an S plan system so it is not the boiler thermostat that has gone faulty, it could however be a zone valve that is jammed open, the motors in them can seize in the open position
 
The current cylinder thermostat is fixed at approx 1/3 - from bottom of the tank. I did try to lower it,
That would make it worse.

but still feels too hot, my kids are saying it’s burning their skin.
60° IS hot but is necessary to combat disease.
You are not supposed to be able to hold your hands under it.

You would need a thermostatic mixer to avoid this.
 
I’ve lowered it to 50 today, and after i think it’s reached the temperature, the motorised valve light goes out and the pump lights stay on. Then I check few minutes later and the pump lights go out as well.

Ian, thank you again, the temperature has always been set at 60, but I recently replaced my pump as it was making a racket. The only other thing I’ve changed (already mentioned the cylinder thermostat) is a mixer valve at the kitchen sink, but wouldn’t think that makes a difference?
 
Last edited:
That would make it worse.


60° IS hot but is necessary to combat disease.
You are not supposed to be able to hold your hands under it.

You would need a thermostatic mixer to avoid this.


Sorry, what would make what worse? So I need thermostatic mixers? Some of my taps are mixing taps (non thermostat types) should I still need these other mixers?
 
Try turning your cylinder stat down with the CH on and feel the DHW zone valve to see if heat is passing through it , it shouldnt
 
Try turning your cylinder stat down with the CH on and feel the DHW zone valve to see if heat is passing through it , it shouldnt

DHW? Central heating on, in this weather, will it work? Or do I just turn it on at the clock?
 

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Sponsored Links
Back
Top