Oil Tank Fill & Vent Piping Size Requirements & Codes

For new oil storage tank installations and in some jurisdictions for upgrading to approval of existing oil tank installations, two model code provisions determine that the oil tank vent pipe should be 2" in diameter.

First, there is a requirement that an oil tank fill piping must be at least 2 inches in diameter.

Second, there is a requirement that oil tank vent piping must not be smaller than the fill pipe.

Here are the model code details:

1305.6 Fill piping.

Fill piping shall comply with the requirements 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.

1305.7 Normal Vent Piping

Normal vent piping shall comply with the requirements of Sections 1305.7.1 through 1305.7.9.

1305.7.1 Size [of normal vent piping on oil storage tanks]

Normal vent sizes shall comply with the sizes listed in Tables 1305.7(1) and 1305.7(2); provided, however, for tanks other than those complying with the alternate tank design and construction standards contained in Section 1305.14, the normal vent shall not be smaller in size than the fill pipe.

Readers question the requirement for 2-inch oil tank fill and vent pipe size

On 2023-03-18 by Anonymous (Bryan) - is a 2-inch oil tank vent pipe mandatory?

Is a 2" vent pipe mandatory? Is there an actual code violation? If so, where's is it? Is it just a recommendation?
If it is truly a problem, why are smaller vent pipes allowed on older installations . Is this an undue burden on the consumer? Are codes different by state and cities?

On 2023-03-18 by InspectApedia Editor (mod) - is a 2-inch oil tank vent pipe mandatory?

@Anonymous,

You don't give country and city of location nor building age.

Yes, in most jurisdictions you need a 2" vent on your oil tank.

Yes, in OLDER installations before the code writers updated the building codes, smaller vents may have been installed.

NO, this is not an undue burden on the consumer.

Just compare the rough cost of changing a few feet of pipe from 1 1/2" to 2" in diameter - perhaps less than $250. depending on where you are located, with the enormously greater cost of an oil spill cleanup if your oil tank bursts and leaks and floods the ground or your building with heating oil - potentially tens of thousands of dollars of cleanup cost.

On 2023-03-1 by Anonymous (Bryan)

@InspectApedia Editor , Thank you for the reply. I checked the International Code council on Fuel Oil Piping, Chapter 13, Fuel Oil and Piping, Section 1305.7 Vent Piping, and there is no requirement for the size of the vent pipe, material.,location but not size.

There are recommendations but no requirement. An undue burden can be defined as a unnecessary expense. The house 68 years old, in Shelton Ct. never with this piping, if it allowable on existing smaller size vent pipe, why would be required to be changed? Also spoke to the city's building inspector, who said it is not a code violation.

On 2023-03-19 by InspectApedia Editor (mod)

@Anonymous, (Bryan)

I gave you the basics above: you're saving a couple of hundred dollars and risking a tens of thousands of dollars oil spill cleanup mess.

Consider that

- oil tanks are filled under pressure at high speed - this actually pressurizes the oil tank during fill-up - we explain this at the start of the article

at OIL TANK FILL & VENT PIPING INSTALLATION & INSPECTION [Ed. this reader exchange was originally posted there.]

- the vent pipe is what relieves that pressure

- particularly at an older home like yours with, presumably, an older oil tank, the risk that the tank has corroded (internally, not visible) so the risk that the tank might leak or even burst during fill-up is increased over when the tank was new

- that's why in some communities, if an oil delivery company sees that an oil vent or both fill and vent are under-sized by modern standards, they'll refuse to deliver oil until the piping is updated.

About your own personal reading of various mechanical or plumbing codes, above on this page we quote code:

1305.6 [Heating Oil Storage Tank] Fill piping.

Fill piping shall comply with the requirements 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.

Our code citation, consumer warnings, and recommendations such as found here, are based on model building codes, five decades of field experience, and thousands of readers who've looked at this data, some of whom have reported disastrous oil spills in their homes.

No one can fully assess the risk that your own oil tank is likely to leak by text nor even by simple visual inspection; there are oil tank testing methods, discussed in this article series, that can address that question.

But considering that the cost of such tests is close to the cost of replacing a few feet of oil tank piping, and that such a test alone won't guarantee that your tank won't leak, in our OPINON - DF - replacing undersized piping, while not an immediate emergency, is an inexpensive step that is well worth taking. Before the flood.

Please understand, Anonymous, that we at InspectApedia have no business nor financial connection with any topic, service, etc. we may discuss at this website. So it's not as if we're trying to scrounge money out of you. It's your home, your money, your oil tank, and your risk.

On 2023-03-21 by Bryan - I don't see a code requirement for a 2" vent pipe

Again thank you for your reply However, I still no actual Code requirement for a 2" VENT pipe. Not Fill pipe.

Tank is less than 5 yrs old. There has been no problem with filling or leaks. I dont like it when someone says its a Code violation, but cant provide any documentation of an actual requirement.

Since you have me some slogans, I Will give you one, If it aint broke, dont fix it.

On 2023-03-21 by InspectApedia Editor (mod) - yes a 2" vent pipe on oil tanks is required by model and adopted codes

@Bryan,

We're sorry that you've had trouble getting through recommended and code-required oil tank fill and vent pipe sizes, and that you missed my earlier, respectful, "slogan-free", reply as well as my explanation of the risk that you take: of a tens of thousands of dollars oil spill cleanup cost.

We also noted that building code requirements vary by country and city, as well as by oil tank size - we still don't have your oil tank size.

On building and plumbing code questions, the local building code compliance inspector is the final legal authority.

For example, here are oil tank fill and vent size requirements in New York City.

Watch out: the code-required oil tank vent size where you live may be different, and the oil tank fill and vent size that your local oil delivery company requires may also be different, from the example below.

Please try to be a bit more polite to people offering researched, unbiased information to you, free for the offing.

As you say your oil tank is just a few years old, if it was installed in a jurisdiction that has adopted the model national codes on oil tank installation, then its vent pipe is in violation of those codes.

If your local building code officials have nothing to require of you about how you vent your old, more-at-risk-for-leaks oil tank, then it's your money and your choice.

On 2023-03-21 by InspectApedia Editor (mod)

@Bryan,

Continuing

1305.7 Normal Vent Piping

Normal vent piping shall comply with the requirements of Sections 1305.7.1 through 1305.7.9.

1305.7.1 Size

Normal vent sizes shall comply with the sizes listed in Tables 1305.7(1) and 1305.7(2); provided, however, for tanks other than those complying with the alternate tank design and construction standards contained in Section 1305.14, the normal vent shall not be smaller in size than the fill pipe.

Since you may be reading bit hastily, Bryan, we'll repeat for clarity for you:

... the normal vent shall not be smaller in size than the fill pipe.

Sources of and copies of oil tank regulations can be found at

OIL TANK REGULATIONS - home

See OIL TANK PRESSURE for a detailed explanation.

...

On 2022-01-26 by Inspectapedia Com Moderator (mod) - oil tank venting codes & requirements come from real world experience

@Linda,

Building codes change as code-writers have more data on failures.

Current requirements for better oil tank fill pipe venting come from that experience, including blown oil tanks and very very expensive oil leaks and spills. The older your oil tank the greater the risk of a catastrophic spill. You may not realize it but oil tanks are filled under-pressure.

Some oil companies will refuse to deliver oil to homes whose fill and vent pipes don't meet current standards because they understand these risks and don't want to be blamed for an expensive oil tank leak and spill cleanup job.

So yes you would be smart to have the oil tank fill and vent updated as needed.

While you're at it have the tank inspected and checked for leaks, leak-risk, and accumulation of sludge or water.

It sounds like trouble for you , I understand, but trouble costing hundreds of dollars is IMO far preferable to trouble costing tens of thousands of dollars.

Question: what is the required size for oil tank fill pipe & vent pipe?

2021-12-13 by Richmond

At OIL TANK FILL & VENT PIPING INSTALLATION & INSPECTION

Is a 1 1/4 inch fill and a 2 inch vent whistle the correct or acceptable setup for a 330 gal inside my basement but piped outside the building ?
Thx

[This question was posted originally

at OIL FILL & VENT PIPING FAQs]

Moderator reply: Best practice: 2" black iron pipe for both fill and vent pipes to the oil tank

@Richmond,

While your local codes (vary by country, city, etc) may permit smaller sizes, best practice is to use 2" pipe for both fill and vent. But I agree that for some oil tank sizes (smaller) and in some jurisdictions, codes may permit and installers may be using 1 1/2" for fill pipe. Check with your heating oil delivery company and install what they recommend.

Here's an example of a code allowing smaller sizes:

• NEW YORK CITY MECHANICAL CODE - 1305.7 NORMAL VENT PIPING - [PDF] excerpted below

You'll see the focus is on venting - not just the vent whistle but the vent pipe size (which I suspect is what you meant) and this code doesn't mention the filler pipe diameter - but as we will show below, other community codes to give sizes for both fill and vent pipes for oil tanks - usually 2" black iron pipe.

The tables below are excerpted from New York City's Mechanical Code 1305.7 Normal Vent Piping, that has adopted the International Mechanical Code (IMC) Chapter 13, Fuel-Oil System Installation.

[Click to enlarge any image]

1305.6 Fill piping.

Fill piping shall comply with the requirements 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.

Example of Code Requiring 2" Oil Tank Fill & Vent Pipes

Continuing with a different oil tank fill and vent piping size code from the Village of Pelham, NY:

Chapter 35. Fire Prevention

Article XII. Oil-Burning Equipment; Fuel Oil

§ 35-77. Piping.

A.
Piping shall run as directly as possible from the storage or supply tank to the burner without sags and shall be so laid that where possible, pipes shall pitch toward the supply tank without traps. Provision shall be made for expansion, contraction, jarring and vibration.

B.
Cross-connections permitting gravity flow from one tank to another shall be prohibited.

C.
Flexible metal hose and couplings, where used in connection with mechanical burners, shall be capable of withstanding a pressure equal to the piping to which it is connected and shall be constructed of fire-resisting materials. Hose shall be no longer than absolutely necessary.

D.
Each fuel-oil tank shall be provided with a separate fill pipe two (2) inches or larger in diameter. Fill pipes, when installed near any building opening, shall be as remote therefrom as practicable so as to prevent liability of flow of oil or vapor through the building opening.

It shall be laid at a descending grade to the storage tank except where the tank is located on higher elevation than the fill pipe terminal. In such cases a check and gate valve shall be placed as near the end of the terminal as it is practical to place it.

E.
Terminals shall be outside of the building in a tight metal box or flush road box so designed as to make access difficult by unauthorized persons.

F.
Where practicable, fill pipes shall terminate at the curbline. In locations where it is impracticable to extend the terminal to the curbline, such terminal shall terminate at such point as the Fire Chief shall designate. Fill pipe shall not be connected to any other pipe.

So you'll find that though I cited exceptions, the most-common current requirement is for 2" diameter oil fill & vent piping

eg

Fill and Product Piping Connections to Domestic Storage Tanks:

The fill pipe material shall be 2 in (50 mm) schedule 40 black steel

Threaded joints in the fill piping shall be made fuel oil-tight using joint compound conforming to CAN/ULC-S642-M, Compounds and Tapes for Threaded Pipe Joints, or equivalent

All connections in copper piping and tubing should be made fuel oil-tight

Product piping connections at any level below the highest level to which the liquid in the tank will rise should be provided with a shut-off valve (ideally a steel ball valve or gate valve) located as close as practicable to the tank shell.

This will allow the fuel supply to the heating appliance to be shut off without excessive draining of ...

On 2022-01-26 by Inspectapedia Com Moderator - requirements for better oil tank fill pipe venting

@Linda,

Building codes change as code-writers have more data on failures.

Current requirements for better oil tank fill pipe venting come from that experience, including blown oil tanks and very very expensive oil leaks and spills. The older your oil tank, the greater the risk of a catastrophic spill. You may not realize it but oil tanks are filled under pressure.

Some oil companies will refuse to deliver oil to homes whose fill and vent pipes don't meet current standards because they understand these risks and don't want to be blamed for an expensive oil tank leak and spill cleanup job.

So yes, you would be smart to have the oil tank fill and vent piping updated as needed.

While you're at it, have the tank inspected and checked for leaks, leak-risk, and accumulation of sludge or water.

It sounds like trouble for you, I understand, but trouble costing hundreds of dollars is IMO far preferable to trouble costing tens of thousands of dollars.

Keep in mind that many factors in older oil tanks such as internal rust or water accumulation increase the risk of an oil tank leak that might be precipitated by the pressure to which the tank is submitted during fill-up. It's the larger diameter vent pipe that minimizes that pressure.

On 2022-01-26 by Linda - my oil tank piping size has to be increased - but I've never had a problem

Lived in my house for over 30 years.the last time my fuel was delivered,my suppliersaid my vent pipe needed.to be 2 inches.never had a problem before.do I need to correct this and how

On 2013-02-01 by Afraid - a one-inch vent pipe is too small

The illustration is very incorrect. A one inch vent is not permitted. In fact, there is much wrong with the illustration in addition to the wrong size vent. Make sure your tank is installed in accordance with the local codes.

Check with your local inspector. Most oil delivery companies should have a trained technician and will provide an inspection at little or no charge. If your installation looks at all like this drawing, your tanks will leak at some time.