Originally Posted by o1marc
There's only 2 rules in plumbing, HOT is on the left, and s**t doesn't go uphill.
Your almost there, as I was taught as a young boy, the plumbers creed goes like this:
Hot is on the left, cold on the right,
S**T flows downhill &
payday is on Friday.
Some might add don't chew your fingernails too, but I think it helps boost the immune system.
As for OP's question, yes, you will want to raise the drain for the shower higher than the top of the tank. If not, as Marc said once the water level in the tank reaches drain height it will back up into the shower. There are small pumps you could use to pump into the tank but you will still need to raise the shower to make them work.
A shallow tank and a backwater or flapper valve on the shower drain could help, This 21 gallon tank is only 5" tall https://www.ntotank.com/21gallon-ron...-tank-x7058428