David Nebenzahl wrote:
On 7/30/2009 10:09 AM JIMMIE spake thus:

From the info I have gathered the life expectancy of a solar water
heate is comparable to a run of the mill non solar water heater. I
would think they should last just about forever. What goes out on
them?

The only thing I can think of is the panels themselves, which could fail
if exposed to freezing temperatures with water in the tubes. However,
there are heat-exchanger systems which have another fluid besides water
(propylene glycol for one) circulating through the panels which are
pretty much immune to freezing.

One piece of advice I can give is to stay far, far away from so-called
"draindown" systems if you live in a freezing climate. These systems are
supposed to drain the water in case of cold weather, but through a small
hole. If the hole clogs, then your panels could go kablooey.

I've been told that draindown systems have trouble with the solenoid
valve magnet coil burning out or the valve freezing and sticking and
the vacuum breaker and air vent valves getting stuck and not letting
the collectors drain or refill. Also for colder climates, systems
running antifreeze through closed-loop heat exchangers aren't as
popular any more, having mostly been replaced by systems that run only
water through the heat exchanger and letting the collector-side water
drain back and out of the collectors every time the pump is turned
off.