I can't get any guidance on "Sunster" water heaters. Did you mean "Sunstar" Or is it a type of solar water heater.
Somewhat popular in Oz is a type of solar shower water heater in the form of a black plastic bag filled with water and left pout in the sun all day. Has it's own spray head and is hoisted up in rigging for shower in cockpit. Needs sun of course. ol'will.
