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What's with the cold Showers?

Have you ever been the last person out of bed and ended up having a cold shower?  Yep.. it sucks.  So let’s discuss why there not enough hot water for your shower?


First some facts

Shower water consumption = approx. 9 litres per min


Shower length per person = approx. 5 minutes


So a 5 minute shower uses = approx 45 litres


5 person flat with 5 showers of 5 minutes = approx. 225 litres


Hot water cylinder size = approx. 180 litres (some are small like 135 litres and some are large like 300 litres)



Wait…What???  How can you use 225 litres of hot water when the cylinder only holds 180 litres?


Well because the hot water cylinder (HWC) is set to about 65 degrees Celsius (minimum of 60º to stop legionella forming).  So at the shower you are mixing 65º degree water from the HWC with cold water to make the temperature that you like to shower in (about 37º).


So as the 65º water is removed from the top of the HWC, cold water from the street fills the HWC from the bottom at around 10º (depending on the season).  So with new cold water mixing with the remaining 65º water in the HWC, the mixed water is being cooled.  As more water is used more cold water is added and eventually the water in the HWC is cooled down to below 37º so the shower feels cold even with shower on full hot.  The HWC will take time to heat the water back up to a decent temperature for a warm shower.


Some solutions to this problem:

Install a bigger HWC:  The downside is the more water capacity you have to heat, the more electricity you will use.


Turn the temperature up in the HWC:  The downside is you will use more electricity to keep the water hotter.


Have shorter showers:  Set a timer in the shower room and set it when you turn the water on.


Stagger shower times throughout the day:  This allows the HWC to heat up again before the next shower.


Shower at the Gym:  This means you don’t pay for any electricity for your shower.

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