those screws and the screwdriver to fit them!

Double-check that you're not mixing incompatible materials: copper, stainless steel, brass and bronze will all work together, but cast iron, galvanized steel, black iron and aluminum won't. Remember, you'll need dielectric unions if you mix-and-match.

4. Calculate fluid volume

This is important in all system types, but especially in pressurized closed-loop installations. You've worked out how long the pipe runs will be in each part of the system; now you need to calculate how much fluid will be in the solar loop .

5. Measure twice, cut once

All installation and construction work should adhere to this old adage (and its metaphorical sense). Try to have spares of as many parts as possible, especially if they are specialist bits of equipment or very common items (which are often easily mislaid). Extra pipe fittings, nails, screws, soldering supplies, lengths of compatible pipe, solar fluid components, fasteners and other such consumables are rarely wasted, especially in the long run, so it's worth stocking up at the start.