Sigma produces solar thermal collectors and storage tanks, so Sigma can guarantee all the segments needed to a solar water heater. Sigma solar water heater components are: collector (s) , hot water storage tank , mounting kit ( for flat or inclined roof ) , anti freezing gel and connection accessories . The thermosiphonic systems are a good choice for simple, cost effective, and maintenance free solar water heating. As far as the pressurized / forced solar water heater: solar station and expansion vessel are added .