I have a two store house with hot water tanks upstairs.
I have to wait 4 minutes for hot water in the furthest faucet or shower, and also when more than one shower is open, there is a variation of very hot water-to cold-to very hot water... in all showers, that is very dangerous, because you can get burned, so we can not use more than one shower at a time ( we have 4 shower).
Also the hot water pressure is very low when more than une faucet or shower in open.
What shoul I do to fix this problem ?

Thank you.

Michel Wainberg.