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All About My Heating Oil Tank

converting from oil to natural gas

Have you ever wondered how heating oil tanks work? Or just want some general knowledge about your heating oil tank? We can dive into that a bit today.

aboveground oil tank

Where is My Oil Coming From?

Generally speaking, there are several very important pieces to the residential heating oil tank. But before we get to that let’s look at the big picture, starting at the top of the supply chain and progressing forward until we reach you.

heating oil tank under a porch

First, there is an oil company who has hundreds of thousands of gallons of oil storage. That oil gets delivered to your local home heating oil supplier and stored sometimes in smaller tanks. From there, a delivery driver has that oil transferred from the large holding tanks to a much smaller delivery truck, then they will bring some of that oil to your house. 

The oil delivery driver will fill your tank, which is just a vessel to hold oil while it is being consumed by your oil-fired furnace or boiler. The oil is piped inside your home and connected to the furnace which will in turn burn the oil and provide you heat, or your boiler will also provide hot water. 

What are the Different Components of My Heating Oil Tank?

Now that we have the general picture, let’s take a closer look at a few of these pieces. 

Heating Oil vs. Diesel

First the heating oil – did you know heating oil is the same as diesel fuel. Home heating oil is dyed a red color so it can easily be distinguished from “on the road” diesel fuel. While it is illegal to put red dyed home heating oil into your diesel-powered car or truck, it is perfectly fine if needed to put diesel fuel into your home heating oil tank. But it is more expensive to do it that way.

The diesel fuel you buy at the fueling/gas station is called “ON-ROAD” diesel, meaning you are paying highway use taxes on the fuel. These highway taxes are NOT added to home heating oil. However, it will not hurt the furnace if you have to dump diesel fuel in the tank if you are low on fuel. The on-road diesel fuel is a green or yellow color. The color is how you tell the difference. 

Anatomy of a Heating Oil Tank

Second, we have the parts and pieces on top and below the heating oil tank. 

Let’s assume we are talking about an aboveground tank either outside your home or in the basement or garage. 

Oil Fill Adapter

First, we have the oil fill adaptor. It is what the delivery driver connects the hose to when they come. This fitting creates a secure airtight connection to help ensure no oil is spilled during the delivery. 

Vent/Gauge Combo

Then we move to what is typically a whistle/vent/gauge combo. This is a very important piece of the tank. The visible gauge tells you if the tank is full, ¾, ½, ¼ or empty, with other measurements in between. This piece of hardware typically doubles as the vent. 

When the oil delivery driver puts oil in the tank, the air inside has to escape. The vent pipe will always have a cap on top of it that resembles a mushroom. Then inside of this device there is a “whistle” that extends a few inches into the tank. As the air passes thru this it makes (obviously) a whistling noise while the oil is being filled in the tank. 

When the tank is full, the oil touches the bottom of the whistle and it stops making any noise and that is how the delivery driver knows to shut off the flow of oil. This is especially handy when your tank is out of view in the basement or garage. 

Additional Openings

There are typically additional holes in the top of the tank as well. Sometimes these additional openings are just “plugged” with steel pipe plugs as they are not needed. Other times you might have another fitting in one of these openings that the copper oil supply and/or return lines are fed into (we’ll get back to that in a minute).

Then, the bottom of the tank (depending on the brand of tank you have) will have another small hole. This is where the oil valve will usually be installed. This will be a brass valve screwed into the tank with a copper line connected to it. This will also let you “shut-off” the oil flow from the tank in the event of a leak or emergency. 

Then depending upon your system at your house you will have either a single-line system or a dual-line system. A single line system will be a supply line only connected to the furnace. This is what transports the heating oil from the tank to the furnace. A dual line system will have a supply and a return. This second line returns excess oil back into the tank. Not all furnaces or tanks have these two lines, nor is it required or necessary. 

So back to the tank. If you have a fitting on top of the tank where two copper lines connect to it, then you have a supply and a return. Or if you have a single line setup, that can come from the bottom valve OR the top. Either way is fine, but it is usually the preferred method, when possible, to have the oil supply coming from the bottom of the tank. That way gravity will help push the oil out of the tank.   

A Word on the Supply Line

Since we are talking about the supply line… These lines on residential properties should always be copper. The size would be either a 3/8” or ½” line and it may have a protective plastic coating over the copper. Then the copper would connect to a fuel filter at the furnace and then to the pump on the furnace. 

That covers the basic tank parts, but what about the tank location? 

Heating Oil Tank Location

If the tank is outside and aboveground, the legs of the tank might be set on top of masonry lintels that support the weight of a full tank. This helps the legs from sinking into the ground. The tank DOES NOT have to have a poured concrete pad to set on. This can be installed if you choose, but it does add a large expense to the project, and it is not required. If the tank is in the garage or basement then it should be installed on the concrete floor. In some jurisdictions the tank may have to be bolted or screwed to the floor. 

If the tank is in a flood zone, it may also have to be strapped down to the ground. This will prevent it from tipping over or floating away in the event of a flood. 

What Does the Color of the Oil Tank Mean?

Why is my tank a different color from my neighbor? Typically, many standard aboveground tanks are a gray color, but black and beige/sand color is also very common to see. The beige color can indicate a tank with a longer warranty. Some tanks are even red, but many times when we see a faded red color tank in Maryland. That’s when we know the tank is very old. 

And one manufacturer even makes tanks with a stainless steel outer shell and cover. They are very nice looking.  

But really, basic steel tanks can be any color the homeowner wants to paint it. As long as the information stickers on the tank are visible, the gauge, fill cap, fill adaptor, and whistle vent (with its classic mushroom cap on top) are left open and unobstructed, the rest of the tank can be painted any color you want.   

Gee, that’s a lot just to get oil to my furnace to have heat or hot water! Yes, it is a lot. So that’s why if you have any problems with your tank, aboveground or underground, let the professionals at GreenTrax handle it. Do not call your plumber or HVAC company and assume they do heating oil tank installations all the time. Most do not. Best leave it to someone who does this every day. 

So, hopefully after reading this you have a better understanding of your home heating oil tank. But if not call GreenTrax and we can help you. 410-439-1085

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More To Explore

The Maryland Department of the Environment is cancelling the reimbursement fund for homeowners with leaking heating oil tanks!

This cancellation takes effect June 30th, 2024. You need to have your buried oil tank removed NOW, so if the tank is leaking you can get reimbursed for remediation costs before the program goes away. Click here for more information on the reimbursement fund as it operates now.

We urge everyone to contact their representatives in Annapolis and the Governors office and tell them DO NOT cancel the homeowner reimbursement fund for leaking residential oil tanks! They can still renew this program before this year’s legislative session ends.

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