Cleaning Water solar panel.

[wayneg]

I am just about to pick up a used solar water panel that I am going to rig up to heat an outdoor spa. I wondered if it is worthwhile or possible to do an internal flush. Thinking fill up with car coolant system flush, leave for a while then run clean water through. Will that damage it and would it be worthwhile? I have no idea.

[wayneg]

If anyone is thinking of heating a spa or pool with an old water panel here is what happened.
I rigged up the panel with a small 12v pump and a 12v solar panel. Using garden hose to circulate the water instantly there is heated water coming out to heat the spa as as expected, result!
After a few hours the water in the spa started taking on a yellow hue so obviously my initial 10 minute flush of the panel before fitting was not enough.
I then filled a big bucket with water and Techaly coolant flush and water circulating the mix through the panel for 12 hrs. The bucket of water looked like mud at the end with obvious limescale deposits. After emptying all and flushing out with clean water it seems I now have no more contaminants within the panel and the water is sparkling clear.
Makes me wonder if the panels on the roof could do with a clean out.