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In parts of this country that do not have natural-gas pipelines, the fuel choices are simple: fuel oil or propane gas. Both of these fuels require the homeowner to store about a month's supply on-site. Propane brings with it some concern about safety and the chance for explosion. Oil is an exceptional fuel if you can get it. It has high heat content and is time-proven.

But oil has always brought with it the issue of how to store it and keep it clean. The burning of oil in residential burners sends oil under high pressure through a highly restrictive nozzle. The oil atomizes into a fine spray and is ignited by a high-voltage electrode. If any impurities get into the oil (such as water, dirt or rust), then combustion can be affected. Oil fumes, inefficiency, and no-heat calls can result.

Part of the problem up to this point has been the way that oil has been stored in the basement. In the United States. The standard oil tank for residential use has been the upright, 275-gallon, plain steel tank (shown in photo at top of page). The steel can rust and leave ferrite sludge (rust) in the bottom of the tank. The resulting sludge can clog filters and fill the bottom of the tank. The tapping, where oil leaves the tank to go to the burner, is at the bottom of the tank — right where the highest concentration of sludge can develop. Another drawback of this design is that the tank is mounted on four steel legs, which of course can also rust. The loss of a leg can cause the tank to tip over, leading to a catastrophic cleanup and major expense.

Plastic to the Rescue

But a vast improvement has emerged from over the horizon. The future of oil storage is now in polyethylene double-wall storage tanks. The advantages of these tanks are many. It is a polyethylene (plastic) tank inside of a galvanized-steel outer shell. Both shells are pressure-tested and liquid-tight. The polyethylene tanks do not rust. The outer shell is tough enough to withstand impact from outside and treated to withstand corrosion from aggressive salt air. There is also a leak-detention device that activates should either tank begin to leak. And the tapping for the oil to leave the tank is up off the bottom so oil sludge can't clog filters.

These polyethylene tanks are not new. They have been in use in Europe since 1971. It's taken almost 20 years to get approval in the United States through the fire-protection boards, but these tanks are now approved everywhere. They are easier to handle and install in the house. They take up less floor space and can be piped together for larger storage needs. The tanks do cost about twice what steel tanks do, but they have an indefinite life expectancy. And the price tag seems less when you consider the potential expense from even the smallest oil spill on your property. Spilled oil is hazardous and requires costly cleanup by accredited professionals at the homeowner's expense.

The manufacturers are certainly confident. They offer a 10-year, full-replacement warranty, and all tanks carry $1 million-per-tank third-party insurance for environmental cleanup cost.

Despite the added cost, the double-wall polyethylene system is a revolutionary improvement over conventional steel tanks for in-home oil storage.

Richard Trethewey is the plumbing and heating consultant for This Old House.

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