What size hot tank is required for a mixer shower?

[danielhowden]

If I fit a mixer shower, how big a hot water tank do I require for it not to run out half way through?

I know it depends on how long I shower for but I have a 110 litre hot water tank and I don't know if it is big enough.

 

[TicklyT]

Depends on the flow rate through the shower, the recovery rate of the cylinder (how long it takes to re-heat), how hot you like your shower, how hot the hot water is and how cold the cold water is.

Ignoring the recovery rate for a moment, the hot cylinder only heats as far down as the bottom primary connection - let's say 80 litres of hot water. If the hot water is at 60 degrees, and the cold is at 10 degrees, equal volumes of hot and cold will give 160 litres of water at 35 degrees.
If the shower delivers 10 litres of water per minute, that will last 16 minutes.

If the recovery time of the cylinder is, say, 40 minutes, the water won't reheat as fast as you use it, but you might get another 5 minutes before running out.