I'm done with vinegar! I let the solution sit overnight, and pulled out the anode rod just now. Wow! It was nearly perfectly clean and scale-less. Better than vinegar ever did. I wish I had one of those flexible snake cameras to look into the tank, but if the anode rod is representative of the rest of the insides, that baby is clean!
$3.50 vs. $20? A no-brainer indeed!
Next time I am buying bulk citric acid at my local kitchen supply store. I'll bet that drops the price to about half again.
Here's a pic. of the anode. Nothing but metal! :
UPDATE: I was in a kitchen store yesterday for another reason, but went ahead and bought a bag of citric acid there. It was less than $2 for 8 oz.
I will also me making home-made dishwasher detergent with it and other ingredints that works better and is far cheaper than commercial products.