The Pump and Controller

Attached to the front of the tank is a Grundfos UPS 15-58 pump. This is a pretty standard cast iron pump for hydronic heating applications that has enough 'head' to ensure good circulation of the fluid at high temperature. It is a three speed pump (selectable) with integrated check valve. On the high setting it achieves about 2gpm flow rate in this setup. It can be isolated from the system using two big ball flange valves for maintenance. The system fill ports and expansion tank can also be seen in this picture.

From My Solar Hot Water System