Thinking of a solar heater project, need input.

I've been thinking (as many have) with the cooler weather that I want a solar heater. Plenty of sun here in FL, right? I decided I've got some spare time and want to take a shot at a DIY project. I found a site with some links to a few other folks DIY projects and I found this one intriguing.

http://www.builditsolar.com/Projects...wCollector.htm

I'm not sure galvanized steel will be a great idea for the collector material with my salt water (currently 3800ppm). Any opinions here?

Among a few other changes to the design I'm contemplating are, I would like to find a way to plumb this in directly with the existing piping. I'm far from competent with hydraulics. Is it reasonable to try and pursue installing a T connector in my existing plumbing with some sort of check valve? Like this design already includes, I definitely want to incorporate the PV panel and dedicated pump.

At first glance, I'd think you'll get better performance from putting up commercially available solar panels yourself. While the free pumping you get from this may seem like a win, 8W is not going to move much water.