Solar water heater life

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?
Jimmie
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On 7/30/2009 10:09 AM JIMMIE spake thus:

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

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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 defects eventually. 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.

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wrote:

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 the system. **********************

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On Thu, 30 Jul 2009 12:53:21 -0700 (PDT), Philip5malin

The best place to get solar collectors is from a roofer. I got my pool collectors from a homeowner who was tired of roof leaks, on a tip from the roofer.
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Philip5malin wrote:

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 use.
I've gotten 6 free solar collectors from homeowners who abandoned their solar heaters.
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John Keiser wrote:

Replacing the anode appropriately will help avoid that.
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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 "forever."
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John Keiser wrote:

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.
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David Nebenzahl wrote:

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.
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JIMMIE wrote:

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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