The only time I get hot water from my new Ariston 30L overhead water heater is when turn it off from the main, then my Ariston will start heating up. Otherwise it's lukewarm at best.

Can anyone help or know what the problem could be?

  • It is a tanked water heater. After you turn it on, it will take 20-30 minutes to warm all the water in the tank. Only then will it be hot. Dec 4, 2022 at 22:27
  • Where is this? Is this a water heater that is designed for batch water heating rather than for keeping a tank of hot water available at any time? Does it drain by gravity or pressure? ("Overhead" suggests gravity draining.) Dec 4, 2022 at 23:57
  • "The only time I get hot water is when turn it off from the main". Does this mean that you're turning off the power to the heater (how I first read it), or turning off the water supply to the heater, or something else entirely? Please edit your question to clarify this point.
    – FreeMan
    Dec 5, 2022 at 13:06

1 Answer 1


I assume you mean when you turn off the water valves:

when turn it off from the main

Which makes me suspect you have a bad thermo-siphoning situation with the valve(s) open, and you need some kind of heat trap to prevent that.

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