Oil tank piping requirements sketch Oil Tank Fill & Vent Piping Installation & Inspection

  • OIL FILL & VENT PIPING - CONTENTS: How to install, inspect, or troubleshoot oil storage tank filler piping. How to install, inspect, or troubleshoot oil storage tank vent piping. What happens if an oil tank vent pipe is too small or clogged
  • POST a QUESTION or READ FAQs about oil fill & vent piping location, diameter, length, routing, connections, leaks, & troubleshooting.
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Oil tank fill & vent piping guide:

Inspection for Above Ground Heating Oil Storage Tanks (ASTs). This heating oil piping article gives advice and example photos for the installation, inspection, & leak troubleshooting of oil tank fill & vent piping for both buried and above ground oil storage tanks.

The page top photo shows a conscientious oil delivery drive from Bottini Oil in Dutchess County NY listening at the oil tank vent to determine when the oil storage tank has been filled. Drivers who don't bother to listen during oil tank fill-up and where there is no loud tank alarm installed are at risk of over-filling the oil tank and causing a spill.

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Heating Oil Fill & Vent Piping installation, inspection, troubleshooting

Photograph of a in-home oil tank - notice the small diameter vent line?

[Click to enlarge any image]

Here are a some important indicators of tank condition that any home owner or home inspector can examine when an oil storage tank is visible and accessible inside or at a building.

Sketch below shows an outdoor above ground oil tank and was provided courtesy of Torongo home inspection and education firm Carson Dunlop Associates.

The oil company recommends going to 2", and most new installations use a two-inch diameter vent pipe; we've seen vent piping as small as one inch on oil tanks. During fill fuel is delivered at an average rate of 60 or even 70 gallons per minute.

Improper or blocked oil tank air exit venting can place excessive stress on tank seams and piping.
See OIL TANK PRESSURE for a detailed explanation.


Oil tank piping requirements sketch Oil filler pipe too far down hill (C) Daniel Friedman Dunedin New Zealand

Above in our photograph an oil fill pipe at a property in Dunedin, New Zealand (South Island) doubles back on itself to give the oil delivery driver a fighting chance at filling an oil tank that is uphill from the point of fill. To me [DF] this is a rather ugly installation that seems likely to lead to a spill.

Oil tank fill and vent piping at an outside wall serving an indoor oil storage tank in a basement (C) Daniel Friedman Undersized oil tank vent piping(C) Daniel Friedman

Plastic oil tank vent pipe (C) Daniel Friedman Glens Falls NY Rust damaged oil tank fill & vent piping = leak risk (C) Daniel Friedman Rhinebeck NY

UST oil tank filler and vent pipes at or below ground (C) Daniel Friedman FDR estate Hyde Park NY UST oil tank filler and vent pipes at or below ground (C) Daniel Friedman FDR estate Hyde Park NY

Oil tank piping requirements sketch

King Fill oil tank vent alarm - also see Durst & Scully

Fill and Vent Piping for Duplex Heating Oil Storage Tanks

Oil tank piping for two tanks (C) Daniel Friedman - Audel

At buildings where two heating oil storage tanks are installed, typically indoors, this Audel Oil Burner Guide sketch shows the proper arrangement of fill piping, vent piping, and oil line piping leaving the tanks.

We have seen an alternative arrangement that provides a fill line only to the first tank, with the second tank filled by a second pipe exiting the top of the first oil tank - not an arrangement we recommend as this forces the first oil tank to be fully pressurized at the oil delivery truck pressure during fill-up of the second tank.

The piping shown in this Audel sketch is better. Details about piping of fill and vent and oil supply lines for duplex oil tanks are

Thanks to Arlene Puentes for technical editing, March 2010.Requirement to Extend Indoor Oil Storage Tank Fill & Vent Pipes to Outside

Reader Question: Feb 18, 2015) Nelle said:

I live in an older building and both my and another tenant's oil tank are located in my garage. The only way to fill them is to open the garage door and come in to do it. I have found one company who is willing to do this but they aren't reliable - they've never come when they've said they would - I don't mean they miss by an hour or two - we're talking a week or more. Another company I approached said they tanks had to be piped outside. Is that a state law, regulation, fire hazard. Does anyone know?

Reply: NFPA 31 8.5.2 (2011) requires that oil fill and vent pipes terminate outdoors, if it is intended to be filled by hose from a fuel delivery vehicle

5/11/15 NHFireBear said:

Nelle: State and local fire codes do vary, but the "national" standard NFPA 31 (Standard for Installation of Oil Burning Equipment) is widely adopted in the USA. Section 8.5.2 of the 2011 edition requires that oil fill and vent pipes terminate outdoors, if it is intended to be filled by hose from a fuel delivery vehicle. If it has a separate funnel inlet for hand filling, the tank, room ventilation, clearance distances, pipes, fire extinguishers and other things must also comply with NFPA 30A Code for Motor-Fuel Dispensing Facilities and Repair Garages. Whether previously approved installations can be used after the code requirement has changed is up to the local authorities, in most cases.

[This question was originally posted at OIL TANKS. NHFireBear is a frequent contributor to - Ec.]

Oil Storage Tank Piping Codes & Standards

The oil tank piping installation and testing standards cited below are the most-widely adopted throughout states and cities in the U.S.

Reader Question: elbows in oil tank fill & vent piping

2015/11/25 Ron said:
How many elbows are code on a fill or vent pipe and if you have too many can it cause a vacuum


Ron I have not seen an explicit limit on elbows on oil tank fill or vent piping, though one would want to keep the number to a minimum. Using the ICC as adopted by New York City as the 2008 NYC Mechanical Code as example we have this:

1305.6 Fill piping. Fill piping shall comply with the require- ments of Sections 1305.6.1 through 1305.6.6.

1305.6.1 Size. Fill piping shall be a minimum of 2 inches (51 mm) in diameter or 3 inches (76 mm) for No. 6 fuel oil.

305.6.2 Termination location. A fill pipe shall terminate outside of a building at or above grade at a point least 2 feet (610 mm) from any building opening and 5 feet (1524 mm) away from any subway grating at the same or lower level. A fill pipe shall terminate in a manner designed to minimize spilling when the filling hose is disconnected. Where No. 6 fuel oil is used, the fill pipe terminal shall be within 3 feet (914 mm) of the curb unless otherwise required by the Department of Transportation or the Transit Authority. If facilities exist for an oil delivery truck to drive onto the pre- mises, the fuel-oil terminal may be located elsewhere other than the curb.

1305.6.3 Separate fill piping. Each storage tank shall be provided with a separate fill pipe, except that where a battery of tanks containing the same grade of oil is installed, a common fill and header pipe may be installed.

Also see NFPA 31 that governs oil tank installation & piping that has similar language:

From NFPA31 as adopted by Warren Co VA

NFPA 31 section 8.2.5

Pipe shall be connected with standard fittings and tubing with fittings of listed types.

Oil Tank Piping Articles

These following articles address avoiding oil spills and leaks by tank installation and maintenance and by oil spill prevention & detection devices


Continue reading at OIL FILL / VENT PIPE LEAKS or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.


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