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
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.
Found--the gene that causes belief in genetic determinism
My panels have lasted 30 years [in Hawaii] but I've had to replace the
plexiglass covers and resolder a joint in the manifold.
A roof top is a harsh environment and poor quality materials will show
My panels feed into a normal 80 gallon water heater for storage. The
heater is 20 years old.
Even though the thermostat is set extremely low and the elements are rarely
activated, I assume the tank will eventually rust and develop leaks.
In my community in Davis, Calif, many residents had solar water
heaters built in when the homes were built 30 years ago. Many of them
disappeared now. I still have mine, but is shut off. First things
many people found is rust in piping, rust on pipe joints, calcium
deposit on heating systems etc, making leaks. It is not fun when it
starts leaking on pipe joints on roof. Second, is roof anchors, many
anchor positions starts to lift up as times goes by, sun heat
expansion, wind lifting anchors etc. Making leaks on roof when rains.
Then many homeowner fed up with it, when they replace the roof, the
roofer does not know how to handle the system, or not want to liable
with it, saying they are not plumber, and they will simply get rid of
I'm in Phoenix, and many solar heaters have disappeared here, too, but
not because their collectors wore out (tempered glass, extruded
aluminum, and copper tubing last forever) or lifted off the roofs but
because pumbers wanted too much to repair them and wanted to install
$900 solar tanks instead of modify regular electric heaters for solar
I've gotten 6 free solar collectors from homeowners who abandoned
their solar heaters.
As far as lasting "forever", I should have added that I had to replace the
Grundflos circulating pump after 30 years [bearing failure] and the delta
temperature control unit after 25 years [triac failure]. No complaints
since these components gave good daily service for decades - but not
Our system was apparently installed in the early 1980s and is still
all original except for the water tank. The March pump needed a new
impeller and the Delta controller still works, although the screws
holding its circuit board came out completely because of vibration.
The controller was built with 100% generic parts and is so simple I
was able to make a copy it. I don't remember there being a triac in
it (freeze protection is through recirculation), but triacs are cheap.
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
Solar heaters are supposed to last longer than regular electric ones
because the heating element doesn't run as much and create really high
temperature spots that make the water boil and precipitate out the
minerals. But I think the main problem is still corrosion that
becomes really bad once the anode rod disappears, so replace it about
every six years. Some heaters have two anode rods.
If you don't like the $900 price of solar water tanks (probably why so
many old solar heating systems have been abandoned -- and why I've
been able to get solar collectors for free), you can use an ordinary
tank, almost unmodified in a 2-tank system (just disconnect the wires
to the heating elements and cover their ends with wire nuts). But
with a 1-tank system you have to disconnect the wires from the lower
heating element, use the drain opening as both the cold water inlet
and the output to the water pump (add a T for the drain valve), and
shorten the dip tube so it extends just 6" below the upper heating
element and use it as the return line from the solar collectors. IOW
cold water at the bottom, hot water out the top, and warm water in the
middle of the tank.
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