fitting a shower pump

[rbrstr]

i know this topic is well covered here, but my question doesnt seem to be?
i have a bristan 50 twin impeller pump due to be connected in my airing cupboard, my hot water storage tank is of what i would call a standard size,as in, its what i've seen in most houses (sorry to be so vague) can anyone give me an approximation of how long my shower can run before using all the hot water?
i know i've probably not given all the info you need here, but if 5 people take a 5 min shower in the morning am i going to be running out of hot water?

 

[kevplumb]

depends on the size of the storage tank

the size of the cylinder

what the water temp is

and the recovery rate of the cylinder

and what colour the tiles are

 

[SUPERPLUMBER]

a 1.4 bar pump fed via 15mm pipes has a flow rate of about 8-10 litres a minute. an average sized hot water cylinder is about 120 litres.

the top 2 3rds of the tank have hot water in it (the hottest at the top and the coolest at the bottom) so lets assume youve got about 80 litres of hot water. so i make it youve got about 8 to 10 mins of hot water.

if you have the boiler on at the same time with a recovery rate of 25 mins(the time it takes to reheat the tank) you could add about another 30 to 40 litres of hot before your passions are truly doused.

This is purely speculative but will give you an idea of how to work it out.

 

[dolph]

Whilst I would not disagree with the above but my own system lasts far longer than the 8/10 minutes mentioned. Thinking about it, it is a mixer shower, and the shower allows the water out at 38 degrees, whereas the hot water in the tank is at 65 degrees. I dont know how much cold has to be mixed with the hot to bring it down, but it must extend the amount of hot being extracted from the hot water cylinder by a significant amount.

 

[dolph]

Whilst I would not disagree with the above but my own system lasts far longer than the 8/10 minutes mentioned. Thinking about it, it is a mixer shower, and the shower allows the water out at 38 degrees, whereas the hot water in the tank is at 65 degrees. I dont know how much cold has to be mixed with the hot to bring it down, but it must extend the amount of hot being extracted from the hot water cylinder by a significant amount.

 

[kevplumb]

yeah but the cold is coming from the same storage tank

so if thats to small