Building a Solar Water Flow System

By Rik DeGunther from Solar Power Your Home For Dummies, 2nd Edition

After you have your solar water collection system in place, you have to move the water to the working apparatus — usually back and forth so you have parallel sets. One pipe is directing water into the collector; the other has the warmed water going back into the workable apparatus.

Here are some tips on choosing your materials:

Pipe makeup: For household systems, copper pipe is the best choice. It's heavy when filled with water, so take care to mount it properly. For swimming pool systems, PVC pipe is the overwhelming choice.
Pipe size: A thick pipe weighs more than a thin one when filled with water. On the other hand, a thick pipe makes your system more efficient because the pump doesn't have to work as hard.
Insulation: Insulation is a must outdoors and highly recommended inside. HT/Armaflex is your best bet. It lasts a long time, indoors and out. Put a plastic jacket over the insulation to shield it from the elements.
Flanges: You need to use flanges to keep the pipe in place. Be mindful of weight loads because flanges often bear the brunt of the forces. Flanges come with weight-load specifications based on proper installation.

Make sure that you map out the flow of fluid before installation. Minimizing the length of runs is desirable for cost and efficiency. Also, bury pipes whenever possible.

Be mindful of the pressures that can build up at the bottom of the pipes if you're running them up to a second- or third-story roof.

To keep the pressures and temperatures where they should be, a number of different valves and monitors are installed in appropriate locations:

Thermometers, flow meters, and pressure gauges: These devices let you see the system parameters.
Check valves: Swing valves allow fluid to flow in only in one direction. The best ones are made of bronze. Because the gate is gravity forced, swing valves work only when they're horizontal or tilted upward.
Pipe unions: These connectors join two pipes without solder or permanent connection. Pipe unions are commonly used to interface with all collectors, so you can remove the collector from the system for servicing.
Drain valves: Drain valves are part of every solar water system because they are the means to drain the fluid out of the system (for maintenance, weather safety, and so on). Ball valves are most reliable; they use a spinning ball with a big hole, constrained in a socket. They're either on or off.
Relief valves: These valves protect against pressure buildup. They're required for every closed-loop system.

Be careful; relief valves can pop open at any time. In general, always use a drainage tube with a relief valve so that if the valve does open, you channel the flow to a safe location, such as under an enclosed porch.
Tempering valves (mixing valves): These valves have three ports: cold in, hot in, and mixed output. A twist handle controls the output temperature at the mixed output, which flows into your home's faucets.
Motorized valves: These valves are controlled electrically. Although some allow you to control water flow, in most system applications, off/on is all that is required, and these valves are cheaper and easier to operate.
Vacuum breakers: Vacuum breakers allow air into a system when it's depressurized. You use them to quickly drain systems, such as rooftop pool collectors.