Discussion: The above picture is for illustrative purposes and shows how a PVC Union is connected to pipe and is place INSIDE THE PCS3 solar pool heater. Both the PCS3 solar pool heater and SolarAttic's prior model PCS2 solar pool heater were designed for use with an LDR Industries PVC Union fitting on both the intake and outflow manifolds. These unions are shown below. In concept, if flex pipe was used in the attic, only a single glued joint would be required in the attic. That joint would be in the form of a quick connect/disconnect LDR PVC Union. This eliminates toxic pvc cementing within a very enclosed attic area with little ventilation.
One side of the union would have a SLIP fitting to be glued to the continuous length of flex pvc pipe using the best flex pvc cement available. This connection could be glued outside of the attic. The other side of the union would require a 2 inch female pipe thread that is connected to the copper intake and outflow manifolds. For best heat transfer and ease of winterization, use the TOP manifold for the intake and the bottom for the outflow.
Obtain silicone sealant from a hardware store and place it on the copper threads. Screw on the female side of the LDR Union until it is hand tight and then tighten it 1/4-1/2 turn further. Wipe off the excess silicone sealant and allow the joint to cure for 24 hours before using it. Tightening the union on the copper too tight could crack the PVC union, so use caution when tightening the fitting as we have described.
Availability: These unions are usually available only in a SLIP x SLIP configuration or in a FIP x FIP configuration as illustrated below. Purchase one union of each type if that is the case and split them in two mating the halves together to get the correct plumbing configuration for the manifolds.
The LDR Industries Unions specified and below only have a 1/2 inch lip on the center ledge of the union when it is mated together. Unions that exceed this ledge lip may not fit inside the heat exchanger. The reason to place the union inside the PCS3 is for leak protection of the joint using the AUTO feature of the GL235 or other solar pool heater control.