Abstract: A low-cost modular designed solar heater for heating a fluid under pressure for a multiplicity of uses. This unit is designed to be built from commercially available standard components. It may be utilized for heating swimming pools, houses, or domestic water sources. It is constructed of pressure-retaining tubing circularly disposed in a container which displays the tubing to the sun rays and coincidentally retains the tubing in the desired shape. The tubing comprises a coil of black material with high heat absorbtivity and a specially treated surface to reduce reflectivity. The inside surface of the retaining container is lined or coated with a highly reflectivity smooth material which reflects the sun's rays onto the heat absorbing tubing. The modular units may have a special clear covering which creates a heat sink inside the units reducing heat losses due to convection.