This article is part of a series: The 12 Days of Solar Pool Heating. 

A cutaway of the iSwim panel showing fully open tubes.

iSwim Solar Pool Heating Panels feature full flow tubes, meaning the tubes that make up the body of the panel are molded into the header during manufacturing, resulting in 100% of the tube cross-section extending into the header and no resistance to flow. The iSwim panel has the lowest resistance to water flow in the industry, and that means better performance for heating your pool.

Other brands use panel bodies that are heat welded to the header or subheader where there are holes drilled to allow water to pass from the individual tubes to the headers. These holes are smaller than the individual tubes, causing restriction that reduces heating performance. Often the heat welds mal-form the holes, making them non-uniform, further restricting flow and causing imbalance. Worse yet, some brands use a subheader that further restricts flow and only uses tiny holes as the conduit from the panel bodies to the header.

The iSwim panel is manufactured using an over-molding technique where the header is molded right over the panel body tubes. This is a superior method, not only resulting in fully open tubes into the header, but also delivering a solid connection between the panel components, eliminating the possibility of leaks at tube-to-header welds.

Other manufacturers will tell you that less restriction causes unbalanced flow, but the truth is that a header of adequate size will have equal pressure across it and the flow rate will be essentially the same in all individual tubes (the flow rate distribution depends on the ratio of the header size to the aggregate tube size). Larger headers, like iSwim’s full 2″ headers provide low pressure differential across the header, resulting in equal flow across the panel array. Opposite end feed and return plumbing also helps to balance the flow across the array. Manufacturers that promote subheaders and restricted tube openings to increase the ratio of header to tube size balance flow at the expense over overall flow rate, reducing performance for any given pump horsepower.

Full flow tubes and a high header to tube size ratio makes iSwim the best performing panel for an existing pool system using a single speed or variable speed pump.

As the flow rate of a solar pool heating collector increases to a point, the efficiency level goes up.