I have used Mack for many years for oil and service to the point of entrusting them with a major upgrade of my home & water heating systems for a high efficiency state of the art system at the cost of $13,500(!). Installation looked great but within 3 months i was subject to basement flooding due to a malfunction and >$4,000 of damages and remediation. I was $2500 out of pocket when Mack and their insurer refused to cover. They offered to give me the defective valve so I could pursue the manufacturer!! I couldnt believe it, how classy!!! So the issue is not that they are technically bad (although), it is that they were unwilling to help a loyal client suffering due to their installation.