Question? Just ask us!
Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair
InspectAPedia ® Home
OIL STORAGE TANKS - home
ABANDONING OIL TANKS
ABOVE GROUND OIL TANK (AST) GUIDE
BURIED OIL TANK (UST) GUIDE
HEATING OIL TYPES & PROPERTIES - home
HOME BUYERS GUIDE TO OIL TANKS
OIL SPILL CLEANUP / PREVENTION
OIL TANK ABANDONING PROCEDURE
OIL TANK INSPECTION & TROUBLESHOOTING
OIL TANK LEAKS & SMELLS
OIL TANK PIPING & PIPING DEFECTS
OIL TANK REGULATIONS
OIL TANK REMOVAL COs
OIL TANK SPILL CLEANUP / PREVENTION
OIL TANK LEAK TEST METHODS
OIL TANK TESTING & REMOVAL COs
OIL TANK WATER CONTAMINATION
How much oil is in the oil storage tank? Heating oil tank gauge installation, reading, testing, repair guide: how much oil is in the heating oil tank? How accurate is the oil tank gauge? This article describes how to find, read, and test the oil gauge on a home heating oil tank.
If your oil fired heating boiler, warm air furnace, or water heater has stopped working, one of the first things to check is whether or not you've run out of fuel. If your oil tank is above ground indoors or outside it should have a fuel level gauge installed similar to the one shown in our photo.
Green links show where you are. © Copyright 2015 InspectApedia.com, All Rights Reserved.
Oil tank gauges are pretty simple to find, recognize, and read. If your heating oil tank is above ground outdoors or indoors, look on top of the tank for a device similar to the one in the photos shown on this page.
If the heating oil tank has been enclosed for cosmetic or other reasons, it may be necessary to make an access door that can be opened to give a view of the oil tank gauge.
If the heating oil tank is inaccessible above ground or buried, remote oil level gauges are available. Installing a remote-reading oil tank gauge permits reading of the oil tank level from an readout device inside the building.
[Click to enlarge any image]
How does an oil tank gauge work?
A float assembly inside the oil tank moves up and down along with the level of oil inside of the oil tank.
As the float assembly moves up or down it pushes a metal rod upwards (oil level in the tank is going up) or lets the metal rod fall down (oil level in the tank is dropping).
On top of the metal rod is an indicator, such as the red plastic disk in our photo at left.
The red plastic disk forms a line inside the oil tank gauge, showing the level of oil in the tank.
In this photo of an oil tank gauge the red disk is sitting above 3/4 - showing that the heating oil level in this oil tank is more than 3/4 full.
Well it's easier than you might think. On most oil tank gauges, the plastic tube that covers the actual moving gauge parts is just screwed into the cast iron base that holds the gauge assembly. Once in a while when we've wondered if our oil tank was really empty, or when an owner has reported that the oil gauge seems to "stick" we've done this simple test.
If you did break the oil tank gauge cover it's not a catastrophe - the heating system will still work, but you should replace it before your next oil delivery because a broken or missing oil tank gauge cover could lead to a costly oil spill during an oil delivery.
Now that the cover over the oil tank gauge has been removed and set aside (where it won't roll under the oil tank and get lost), and presuming your tank gauge is not already sitting at the bottom of its range of travel (empty), just press the top of the gauge indicator rod downwards slowly and gently.
You will feel a little resistance because you're pushing a rod and float down into the heating oil inside tank. When you have pushed the indicator partly or all the way down, release it.
You should see the tank gauge rise back to about where it was before.
This tells you that the hinged mechanism and float are still in place and that they are moving without obstruction.
If the gauge is broken, lost, or damaged, the entire assembly can be replaced by your heating oil technician.
Remember that a heating oil tank gauge is not lab-grade equipment. It is not precise to the quart, probably not even to the gallon.
We have made a video of the procedure for testing an oil tank gauge and will post it here soon.
Typically the oil tank gauge vial is a screw-in part obtainable from your oil heat service dealer or from online oil tank gauge parts suppliers. - thanks to reader GC for this comment. <
Here is a gauge on an outdoor oil tank. The red button resting at the bottom of the plastic tube to left of the galvanized tank vent pipe shows that this oil tank is probably empty.
This is a poorly installed oil tank, exposed to roof runoff, freezing temperatures, improperly closed vent opening, and more.
Check to assure that the oil tank gauge is present, and that its protective cover is tight. Loose or broken oil tank gauges can cause spills during tank fill operations.
How to Find Out How Much Oil is in a Buried Oil Tank or an Above Ground Oil Storage Tank that is Missing its Gauge?
The depth of the oil in the tank is measured by marking the top of the tank on the stick or oil tank gauge, then placing the stick into the oil tank and withdrawing it. The oil level seen on the stick is compared with the distance from bottom of the stick (bottom of the oil tank) to top of the oil tank (which we marked on the stick).
In the old days people kept an oil tank stick that was already marked and calibrated to tell them how much oil was in their tank. Today if we use a folding measuring rule or a generic "stick" to "stick the oil tank" to check oil level, we need to know the volume and shape of the tank as well as the depth of oil on the stick in order to calculate the number of gallons in the oil tank accurately.
In the photo our client is discovering a surprise buried oil tank at a farm we were inspecting.
Some buried oil tank systems use an oil tank gauge that measures oil in the tank and gives a reading at a remote location such as indoors near the heating boiler - which is pretty convenient in nasty weather.
Our photo shows an antique gauge used with a buried oil tank. Modern remote oil tank gauges include sensors which provide an LED or an electronic indication of the level of oil in the buried or remote oil tank.
But roughly, the oil tank stick procedure can tell us if the tank is half full, 3/4 full, or nearly empty.
Conventional float type oil storage tank gauges are not precise in reporting the quantity of oil remaining in the tank.
A heating oil tank gauge does a fine job of telling you the oil level in the oil storage tank: oil is near the top, 3/4 full, 1/2 full, or just 1/4 full or nearly empty. Sketch at left showing the location oil tank gauge and of places to watch for oil tank leaks is courtesy of Carson Dunlop Associates.
"Full" in this case just means the level of oil in the tank, not an accurate read of the number of gallons of heating oil remaining.
Oil tank gauges are not accurate in reading the quantity of oil in a tank in gallons or liters. But then neither is the gas gauge in your car - and for the same reason. The tank shape.
What's inaccurate about all oil tank gauges is that because most oil tanks are not square but round or oval, knowing the height of oil in the tank does not tell us very accurately just how much oil is in the tank except at three points:
Scully produces the "Golden Gallon Gauge" that can provide an accurate readout of the level of oil in indoor our outdoor oil storage tanks, including buried oil tanks.
Scully gauges are a double float that communicates to an oil tank level gauge that can be read in inches, gallons, imperial gallons, or liters.
The Scully oil tank float gauge fits oil tank tapped openings of 1 1/2" or 2" diameter (NPT), and can handle oil tanks up to 60" in tank depth (from gauge mount to tank bottom).
Scully's product literature indicates that this is the most accurate oil tank gauge of its type.
Contact the Scully Signal Company.
Reader Question: accuracy of oil tank gauges
When we bought our house, our (oval 275 gal) tank had a reading of about 7/8 (halfway between F and 3/4) and our oil company estimated this to be 190 gals, which would be closer to 2/3 than 7/8 and certainly below 3/4, which it was not. We used this oil from the time we bought it, through the end of last year's heating season until the end of this September.
At this point, we had about 1/8 of a tank. We received a fill-up, which was for 203 gallons and put us at full. It would reason that with an oval tank, the round parts at the top and bottom (round parts) would hold less oil per vertical inch than the middle (straight parts).
That being said, it seems like the top 1/8 and bottom 1/8 combined hold about 150 gallons, or half a tank's worth. Other than this, our oil gauge seems to be reading fine, in that it went from full to half over the course of late September to today (middle of December). I just got a fill up and my tank was reading almost exactly at 1/2, but it was only 100 gallons to fill it.
I have 2 275 gallon oil tanks. I had 150 gallons of oil delivered when the gauge showed I had just less than an 1/8th of oil in the tank. After the 150 gallons was put in the gauge went just above 1/8th. How is that possible? 150 gallons represents 1/4th of the tank and the tank already had oil in it? - Carl 6/20/2012
(Oct 2, 2014) jen said:
I have two 275 connected tanks with one gauge. My gauge read 3/8 so I ordered 275 gallons. The driver was only able to fill to 183 gallons and told me my tanks were full. I understand that although my tanks read 275 gallons, it is actually 260 which goes into each of them. Since the reading was at 3/8, I should have easily been able to hold the 275 (137.5 in each). I believe I may have a blockage but my oil company does not feel as such. Thoughts??
RJ, there are a few sources of confusion about just how much oil a particular oil tank holds, how much is in it at any given moment, and about just how near to capacity the oil company fills the oil storage tank during delivery.
Maybe so, Carl. Consider that especially when filling the lower section (or top section) of an ovate oil tank, the gauge, which moves linearly, can't accurately reflect the actual tank amount. The gauge is accurate only at 3 points: empty, half empty, and full.
Reader Question: how do I read the oil tank gauge against the scale: from the top, center, or bottom of the plastic disc?
The following photo is from your site and is just like mine. It has a disc in a tube like the one below and red marks on tube as shown. The disc is like a checker. And I was wondering if you read the top edge or bottom of checker. - Cliff by email 12/5/2012
Now that you sent us our own photo and an email query I understand the question better.
Watch out: as we get near the bottom of the oil tank, because of that ovate shape, the oil level falls more rapidly than while we're using oil from a tank filled around mid-way.
Watch out: for oil storage tanks whose fuel lines are taken off of the top of the oil tank, the installer almost never places the oil pick-up line all the way at the bottom of the tank. Typically the line is kept a several inches or even more above the tank bottom in order to avoid picking up sludge or water that might be sent to (and foul) the oil burner.
For this reason, we never use the very last bit of oil in the storage tank. This means that for practical purposes (actually being able to draw oil from the tank) that last 1/4 or 1/8 of an oil tank level showing on the oil tank gauge may in fact be very close to TANK EMPTY.
Reader Question: how do I read the oil tank gauge?
[Click to enlarge any image]
Generally we read the center of the plastic disc against the scale. I know this sounds like begging the question, but oil gauges are just not that precise.
Watch out. You are risking a more fundamental error. The oil tank gauge is not accurate anywhere near the range of precision of your question unless your oil tank is a cube or rectangle rather than the oval cross section most often installed.
Search InspectAPedia for Oil tank gauge accuracy for details and for the math used to calculate oil tank volume for oval tanks.
At 1/4 tank remaining and especially if the oil lines exit at the top of the tank (meaning the tank is never fully emptied anyway) its time to call for an oil delivery.
Continue reading at HEATING OIL USAGE RATE or select a topic from the More Reading links shown below.
Suggested citation for this web page
Green link shows where you are in this article series.
Frequently Asked Questions (FAQs)
Question: replacement oil tank gauge parts
The plastic cover that covers (shows the 1/8 markings) the gauge of my oil tank broke/cracked.
I have got a Worcester Camray 5 which is located in the garden. I had an indoor plug in oil level indicator but it has gone missing - where can I get a replacement one please. - Karen Gallant 6/27/12
The plastic part that covers your oil tank gauge is called the gauge vial. You can get one from a local oil heating equipment parts supplier or online. At oil storage tank gauge vials [above in this article] we have added photos and details. - Reader G.C. [Thanks GC] .
Karen the Worcester Camray 5 is a discontinued oil fired heating boiler. I don't know about the oil level indicator you cite - but if it is a device mounted on your oil piping or oil tank, I would imagine your oil heat service company can install a generic replacement.
Question: oil tank gauge not working
Question on a fuel oil tank gauge: 275 gallon outside, vertical, 8 years old, in good repair. Sees Maryland winters.
It was heavily coated inside, almost opaque, a bright red hardened gum. Then gently pushed the float down into a full tank, cycled this slowly several times full range, and it worked for almost a season. Now with the last fill up, it again is stuck on empty. Is there a gum in No 2 FO? Does it splash up and glue the float mechanism? How often does the gauge need maintenance? Mr. R.L. Hails Sr. P.E. 2/25/2012
Oil tank gauges often work reliably for decades and do not require maintenance. On occasion if a gauge stops working it's possible to free up stuck parts by simply moving the gauge operating parts a bit. If that doesn't work, replace the gauge.
Question: oil tank gauge does not return to full position even though tank is full
I have a float gage (319 gallon indoor oval tank), the tank went empty and was filled with 200 gallons however the gage did not return to show approximately 3/4 full. Is it because there is liquid sitting on top of the float gage? If so, is there a way to correct this so the tank reads accurately? - Ian 8/7/12
Question: what is an oil tank whistle and how does it relate to oil deliveries?
Oil won't be delivered unless the tank gives out a whistle, please explain since I'm new at this. and what can I do. Thanks. - Felix S 11/12/12
(Dec 20, 2012) Joe said:
I recently bought a forclosed home that was built in 1957 with oil heat. The house is a 1700 sq feet brick ranck home. The oil was at 5/8 full when I moved in. I have been working on it for 4 hours a day at 60 degrees. I turn it down to 50 degrees when I leave. In one week I checked the gage and it was at 3/8s of a tank. I cant imagine it sucking that much oil. It is really bothering me how unbelievable ineffecient it is. Does anyone have any advise?
(Jan 1, 2013) Darlene said:
I had 1/2 oil in my tank,I then got 100gal and the gauge stayed at 1/2,so I went and got a new gauge and it seems to stay at 3/4. It does not more?
(Jan 1, 2013) Karen said:
Our oil tank has just gone a sliver below the 1/4 mark. Our landlord has always told us never to let this happen. Due to the holidays and financial difficulty, we cannot get oil for 3-4 days from today(12/31). Is something terrible going to happen? Im very worried. This is the first time in 10 years this has ever happened. Any thoughts?
(Jan 4, 2013) todd said:
joe, your furnace is working harder to get to 60 from 50 than say from 56 to 60 ,leave it a higher setting than 50 or try smaller lncrements
(Jan 4, 2013) todd said:
Darlene… as stated above gauges are not 100% correct 3/4 is the safe fill level,in 10 years as a oil truck driver a gauge that reads 1/2 will take only 100 gallons, your tank is at max capacity
(Jan 4, 2013) todd said:
Karen you can put 5 to 10 gallons of diesel fuel to last 1 or 2 days (20 to 40 dollars)
Question: oil tank filled yesterday now gauge says empty
(Jan 4, 2013) Stan said:
My oil tank was half full and yesterday I had it filled to the max. This morning the gauge reads empty?
(Jan 4, 2013) todd said:
Stan check for leaks then check for sticking gauge
Question: how to replace an oil tank guage where space is limited
(Feb 26, 2013) Robin A said:
I have a 275 G tank without a TLI. The 1.5" vent line has a capped end that I stick a stick in to see what the level of oil is. The top of the capped nipple is about 10" above the top of the tank. Can I just stick a TLI in this hole? I have found a couple examples that I think will work such as the Krueger Sentry Galvanized Direct Reading Gauge. It indicates it has a "tank depth" of 6" and I'm not sure what that means. I also found a similar gauge that has a "tank depth" of 10" - not sure what that means either. Can you help? Thanks!
Most likely the oil tank fuel level gauges you describe, when they refer to a "tank depth of 10" " are saying that the gauge can measure oil level in a tank at depths anywhere *between* 10" and a deeper level, typicalliy 144".
You need room above the tank to insert the new gauge and you'll be all set.
There are various LED and other electronic oil tank fuel level gauges that permit remote reading of the level of oil in the tank, but all of them require some sort of sensor or float inside the tank where the oil level will be monitored.
Krueger, the company you mentioned, provides an "LED at a Glance" LED Clamp-on device that will convert the position of the float gauge indicator into an electronic signal of oil level that can then be read by a remote display - that feature may not be one you need.
Contact Krueger directly at
Telephone: USA 1-920-434-8860
Question: missing oil tank gauge vial
(Sept 9, 2014) Rob R said:
the gauge vial on my tank is broken/missing. The sending unit is working perfectly so I am able to guestimate the gallons of fuel in my tank. I have searched for a replacement vial online but they all are threaded vials. Mu issue is that my gauge is held onto my tank with four small screws. You have a photo of the type that I have as the first picture under your " How do we know that the oil tank gauge is working?" paragraph. There are no threads on the gauge mounting hole. Can you provide any insight on how to replace this type of gauge or vial?
It may be most simple to replace the entire oil tank gauge assembly rather than waste a lot of time looking for an obsolete part. Krueger, mentioned below sells a variety of oil tank float gauges and tank bushings that will probably work fine for you.
Or use our email found at our CONTACT link and send me some sharp photos of your gauge and I'll see what I can find for it.
Question: leaky oil storage tank gauge
J. Ross Keys said:
If a supplier overfills a oil tank in the basement of a dwelling and the fill pipe is full, is it possible that the hydraulic head of the liquid above the gauge would leak oil? In other words if a plastic level gauge is installed correctly, what pressure rating are they designed to hold under manufacturing testing?
Definitely. Oil tank gauges, depending on the type and design, can leak if an oil storage tank is overfilled. I think that the leakage will be more severe during fill-up as the tank is being filled under pressure, applying greater oil pressure to the gauge and its seals than just that from the head of oil remaining in a fill pipe afterwards. Examples are in the article above.
Use the "Click to Show or Hide FAQs" link just above to see recently-posted questions, comments, replies, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
Search the InspectApedia website
HTML Comment Box is loading comments...
Technical Reviewers & References