“Boy! How am I supposed to defend my guy against this?” the lawyer groaned. “He pulled the oil-burner permit and started up the burner when the house was built in 1995, but the plumber had already put in the copper oil line from the tank to the burner, running under the slab. My guy never saw the line before the slab was poured, but he could see the copper line coming up out of the slab on both ends inside a corrugated plastic sleeve, just like the code requires. He hooked it up, started the burner, and sold them oil until July 2000.

“The next thing he knows,” the lawyer continued, “he's being sued. The new oil heater fills the tank on Sept. 8, and it's empty again on Sept. 27. He sees oil stains on a patch in the basement floor near the boiler, digs it up, and finds the plastic sleeve has been cut and a compression connector installed in the copper line. The connector was overtightened, and it leaked. He puts in a new overhead oil line, fills the tank, and gets the burner back on. But all that oil has contaminated the ground. Now the homeowner's insurance company says that connector was always there and always leaking, and since my guy had the permit, they want him to pay for all the environmental remediation. How am I supposed to show that the connector was put in later and not by my guy? How can anyone tell when the leak occurred?”

I thought about that for a while and then analyzed the oil-delivery records, the service records, and the weather records. Oil use for heating should be proportional to heating degree days. After all, that is how the oil company knows when your tank needs to be filled. This was a little more complicated because the same boiler also used oil to make domestic hot water. But looking at average oil use per day during the summer, when there was no heating, let me make a pretty good estimate of how much oil was used to make hot water. Subtracting the hot-water use from each oil delivery and comparing it with the weather data gave me the graph of gallons per degree day vs. time in Figure 1.

Any question when the leak occurred?
David M. Elovitz
Energy Economics Inc.
Natick, Mass.

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