Hayward Heat Pro repeated coil failures

When we installed our 5000 gallon in ground pool about ten or so years ago we installed a Hayward HP21002 heat pump to the tune of about $3500...
It worked just fine however after about five years the coil eroded away and disintegrated so we replaced it at the cost of aprox. $3200...
Well now about another 5 years later it has done the same thing and I do not want to spend that kind of money again, heck...that's $6000-$7000 for ten years...that's way too much...

This time I did a little research and found that I can buy just the coil for $600 - $700...

Problem is that I don't know where which online vendors are good and which are not... I would post some pix here but apparently I do not have permission to do that probably because I am a newbie here...

Is that the life expectancy of these coils...? Doesn't seem very long to me for the kind of money they cost...

Any info and/or advise would be very appreciated...

1. Here's the product brochure: http://www.hayward-pool.com/pdf/lite...Brochure13.pdf . If the description there is accurate, there is no way you should be seeing that sort of failure.

2. You can post pictures using Picasa, Webshots, Flickr, etc.

3. Odds are, there's a problem with your water chemistry OR the way you are adding chlorine to your pool.
=> Are you using a K2006? If not, get one. Either way, post results once you have one.
=> How are you chlorinating? Is there any chlorine feed process (feeder, SWCG, chlorine tab in skimmer) that is UPSTREAM of your heat pump?
=> Are you storing pool chemicals near the heat pump?

4. Here's the Hayward parts breakdown: www.hayward-pool.com/pdf/Parts Diagrams/HeatPro.pdf
Are you talking about part #11 or part #13? Failures with #11 are more likely to be environment (chemicals stored near heat pump); #13 is more likely a pool water problem.

You can get a Taylor K-2006 (or 2006C) that Ben mentioned above through the test kit link in his signature above.

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