This is a design for a pool heating collector from Matt that uses conventional PVC pipe.
The manifolds are made from large diameter PVC and the absorber from half inch PVC pipe.
As Matt points out, this construction may be a good alternative to conventional plastic mat style pool heating collectors in areas where these collectors are hard to get, or when you want to fit the collector to a particular area you have available. The PVC pipe is readily available almost anywhere and the end cost is quite competitive.
In a nutshell, the headers are drilled and taped for half inch threaded pipe. Then PVC male threaded adaptors are screwed into the threaded holes in the manifold, and solvent welded to half inch PVC risers. Nice and simple and strong, and can be made to fit just about any available shape.
From Matt's pdf showing the tools and fittings.
Download Matt's good, detailed instructions on how to size and build this collector...