We have two 8ft x 4ft panels that heat our water using the sun. Over the past few months, both have sprung leaks. When the first happened, we did nothing except turn it off, as our water is more than sufficiently heated with just one. But when the second broke too, we had to fix it, and fast - there was a time when we took cold showers without thinking twice, but once you get used to certain luxuries, there's no going back...um...for the sake of the children!
So, what was the problem? Basically, these panels are old. In fact, they were on their way to the dump when Abe's dad rescued them for us. The copper inside gave out in a couple of places and consequently leaked. We could have soldered the leaks closed, but we figured it would just happen again.
We ripped out all the copper tubing (which has copper fins attached to them to help collect the heat better) and slit the tube open. We then attached 6 fins (with slit open tubes in their center) to plywood that we screwed into each side of the panel. We then placed high temperature PEX pipe inside the copper, hammered the copper shut and painted it all black.
They work a treat. At full sun, one panel gets our 1000 gallon hot water tank to 110-115 degrees, two panels to 118-125 degrees. And the beauty of it is that there are no joins now inside the panel, so if a problem occurs in the future, we won't have to take the panels down to fix it.
We have enough copper to make an 8ft x 6ft panel from scratch. When we do that (probably when we build our bedroom in a couple of years!) we will post full instructions.