Unfortunately, Tom, the buyer now has an excuse to back out of the deal, and in my humble opinion you should honor his request for a refund. I think it's pretty crappy of him to do that, but he is within his rights. The only silver lining I see in that cloud is that by refunding his money and taking the tank back it will bolster your reputation as a man that does what is necessary to ensure a satisfied customer.

Personally I think the guy's an idjit. Your offer was more than fair and if it were me I'd have been satisfied with your solution. He's passing up the opportunity to have a tank built by one of our finest builders. However, the bottom line is that the tank he received isn't the same as the tank he bought, so no matter how much I'd enjoy punching him in the nose, I recommend that you take the high road and get the tank back.

Just out of curiosity, what kind of tank is it?