Hot water lasts for less than 5 minutes

[MasterPlumbers]

Hi, I have a Rheem Rheemglas 101080.
It has 80L capacity, but when I have showers the water only stays hot for less than 5 minutes.

I moved into this apartment not long ago, and i cant figure out why it does this. There are a couple pressure valves on the lines going into it and the hot water wouldnt work at all until i fiddled with one and it squirted a bit of water out. Please help I love hot water

[Selgas]

Hi there, to understand this situation lets do some simple math on the matter, the cylinder holds 80 litres of hot water of which only 80% of that storage capacity can be readilt used due to the fact that when hot water is drawn from the cylinder cold water is introduced to be heated, the result is that 20% of the water in the tank will chill down with the cold water making 80% usable as hot water. So 80% of 80 litres = 64 usable litres of hot water. A good shower will require around 10 – 12 litres of hot water per minute so doing the math you will see that the shower would last (at 10 litres/minute) for 6.4 minutes until the hot water is chilled down by the incomming cold water into the tank.
So the simple answer is the tank can only supply enough hot water for the 5 – m6 minutes of shower time, to get a better result a larger storage tank is the only answer to the duration period of the shower.

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Selgas Services Ltd
Craftsman Gasfitters, Plumbers, Electrical Service Technicians

[Robert Stephen Morton]

Pete, it amazes me that you are able to do that, did you substitute sheep for litres in the calcs?

Bob

[Selgas]

Bob

Heck no I used roos cause they is way bigger and easier to count wiff my fingers lol.

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Selgas Services Ltd
Craftsman Gasfitters, Plumbers, Electrical Service Technicians

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