This is a very nicely done solar water heating system that generally follows the $1K design, but has a lot of excess capacity that can be used for hot tub or space heating purposes.Ken was able to get a set of older, but unused collectors from Craig’s list.  The six collectors provide  nearly 200 square feet of collector area, so the system has excess capacity that Ken plans to use for hot tub heating and/or space heating.

The tank is a very nicely done EPDM rubber lined tank with a capacity of nearly 500 gallons.  The design details on the tank are very nicely done, and it should be a good source of design information if you are building a tank for your system.
The PEX coil heat exchanger has been recoiled for improved heat transfer.