The hot water on all taps and showers runs cold under 2 minutes. The boiler is fed from an Aga and the pipes to the boiler are piping hot. When I turn on the hot water it turns cold. I have isolated the taps in the bathrooms in case the mixer was passing. I have an electric Heat Store Aqua Power shower upstairs, could this be where the problem lies?? There seems to be communication between the hot and cold water
Hot water turns cold after 2 minutes
- Thread starter HarryT
- Start date
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OK, thanks. A typical hot water cylinder holds about 100 litres of hot water, provided it has been heated up for long enough (Agas are quite low power and may take many hours to heat it fully - how many hours has the Aga been running with no hot water used?)
Is the cylinder, and the pipes to and from the Aga, well-insulated? What sort of insulation? Feel the primary flow and return pipes at the cylinder, and see how hot they are. They shoul be too hot to hold. Then feel the flow and return pipes at the Aga.
Is the primary flow from Aga to Cylinder pumped, or gravity flow? How hot is the pump?
When the water runs cold, feel the cylinder again, top, middle and bottom, and see how hot it is. You may have to cut or move the insulation to do this.
Presumably the HW Cylinder is fed from a cold tank in the loft? Does the cold tap water come from the same tank, or from the mains? Does the cold tank seem unexpectedly warm?l
Look at all your mixer taps, on sink, shower, bath, basin, bidet etc. Run each hot tap until it comes cold. Then after 5 minutes feel the hot pipe that goes to the tap, and see if it is still warm, or if any of them have gone daed cold (thsi can happen due to backflow, it is espoecially common with ceramic taps)
When was the hot water supply last working properly? What has changed since then? Does the Aga also run a towel rail or radiators? How hot are they? Does the HWCylinder aslo have an immersion heater? Does that give better results?
Does your power shower have a pump, and has it been running? It should have isolation valves, if you turn these off, does the situation imporove? Or does it run at mains pressure?
Is the cylinder, and the pipes to and from the Aga, well-insulated? What sort of insulation? Feel the primary flow and return pipes at the cylinder, and see how hot they are. They shoul be too hot to hold. Then feel the flow and return pipes at the Aga.
Is the primary flow from Aga to Cylinder pumped, or gravity flow? How hot is the pump?
When the water runs cold, feel the cylinder again, top, middle and bottom, and see how hot it is. You may have to cut or move the insulation to do this.
Presumably the HW Cylinder is fed from a cold tank in the loft? Does the cold tap water come from the same tank, or from the mains? Does the cold tank seem unexpectedly warm?l
Look at all your mixer taps, on sink, shower, bath, basin, bidet etc. Run each hot tap until it comes cold. Then after 5 minutes feel the hot pipe that goes to the tap, and see if it is still warm, or if any of them have gone daed cold (thsi can happen due to backflow, it is espoecially common with ceramic taps)
When was the hot water supply last working properly? What has changed since then? Does the Aga also run a towel rail or radiators? How hot are they? Does the HWCylinder aslo have an immersion heater? Does that give better results?
Does your power shower have a pump, and has it been running? It should have isolation valves, if you turn these off, does the situation imporove? Or does it run at mains pressure?
The cylinder holds 103 litres and the Aga is on 24/7 it is never off
The pipes at the Aga are too hot too hold
The flow from the Aga is gravity flow
I ran the taps again and the cylinder was hot at the bottom and middle but not so hot at the top.
Cylinder is fed from tank in loft, not mains feed. Cold water is from mains.
Ran all taps until cold water came out and the hot pipe to the hot tap was cold, taps are not ceramic
Last working Sunday night and nothing has changed. The Aga does not run a towel rail
The cylinder has an immersion heater 800 x 450 but results are the same
The shower has a pump and it runs. I removed the front cover to check and it does not run on mains pressure
I can't find isolation valves for the shower. When the shower goes on at first you usually here something kick in and the water goes hot, I don't here anything kicking in
The pipes at the Aga are too hot too hold
The flow from the Aga is gravity flow
I ran the taps again and the cylinder was hot at the bottom and middle but not so hot at the top.
Cylinder is fed from tank in loft, not mains feed. Cold water is from mains.
Ran all taps until cold water came out and the hot pipe to the hot tap was cold, taps are not ceramic
Last working Sunday night and nothing has changed. The Aga does not run a towel rail
The cylinder has an immersion heater 800 x 450 but results are the same
The shower has a pump and it runs. I removed the front cover to check and it does not run on mains pressure
I can't find isolation valves for the shower. When the shower goes on at first you usually here something kick in and the water goes hot, I don't here anything kicking in
Aha!
That certainly sounds like cold water is back-feeding to your cylinder.
It is most likely a mixer tap that has a mains-pressure cold supply. Feel all the pipes under your taps, you will probably find a "hot" pipe that is surprisingly cold. If you have service valves on your taps you can temporarily turn off the faulty one as a test.
It is possible to fit a backflow-prevention valve, but these reduce flow so if I were you I would replace the leaky mixer.
Thank you for all your assistance. I checked the expansion tank and found that the bracket holding up the expansion pipe had broken and the pipe was submerged in the tank. I have now shortened the pipe and have tested the water and now all is back to normal. Thank you once again for all your help.
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