Thanks for the replies everyone. I never thought of the expansion tank. We had an issue with the hot water heater in Jan of 2010. The pressure release valve got stuck open, and hot water poured out in the basement. Luckily, we were home and I can't imagine it was going on for more than an hour, so it wasn't a huge deal, but the valve and the expansion tank were replaced at that time.
I'll check out the little test procedure anyway. For now, the hammer arresters have done the trick.
Thanks for the info/explanations.--
He used to say that soul shine, is better than sunshine, better than moonshine, damn sure better than rain.
Debunking the 2012 hysteria. | Always looking for a new job | Begging the Wilpons to sell the Mets.