Heating oil tank gauge inspection, defects, repair guide
A simple cure for some oil tank leaks at
Our site offers impartial, unbiased advice without conflicts of interest.
We will block advertisements which we discover or readers inform us are associated with bad business practices,
false-advertising, or junk science. Our contact info is at
InspectAPedia.com/appointment.htm.
This article describes how to find, read, and test the 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.
How to Find, Read, and Test an Oil Tank Fuel Level Gauge
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.
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.
How do we know that the oil tank gauge is working?
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.
Unscrew the plastic cover by hand. Don't grab it with Vise Grips™ or you'll probably break the plastic. The gauge cover turns counter-clockwise to remove it.
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.
What else goes wrong with heating oil tank gauges?
Water leaks: On an outdoor oil tank the gauge may be damaged or simply not well sealed, permitting water to leak into the heating oil tank - a cause of oil tank leaks, rust, and more immediately, water in heating oil can lead to loss of heat. Our photo below shows an oil level gauge on an outdoor oil tank exposed to roof spillage.
Oil tank leaks at pipe fittings: if the oil tank gauge cover is damaged heating oil may be forced out of the oil tank during the oil tank fill-up operation. During oil tank fill-up oil may also seep out of pipe fittings at the top of the oil tank. If oil tank leaks at these locations are severe the pipes need to be removed and the connection re-made with a top quality pipe sealing compound that is oil resistant.
Our oil tank video posted at YouTube explains when, where, why, and how to stop an oil tank at this location.
Other places to look for oil tank leaks are shown in our oil tank sketch below. OIL TANK LEAK ADVICE contains detailed advice about leaky oil tanks.
If the oil tank leak at the top of an oil tank is minor seepage, you may want to avoid the trouble of disassembling and resassembling all of the pipe fittings. On the seeping oil tank fittings in our photograph, we left a rag tied around the leaky pipe. The leak was at the pipe fittings not the oil tank gauge.
The amount of seepage was just an ounce or so during fillup - the rag stopped oil from running down the sides of the oil tank and stinking up the garage where the tank was located. Once a year the owner replaces the dirty rag with a clean one. Paint-on sealants or epoxy applied to a surface which has been thoroughly cleaned of oil residue might also work in this location if the leak is really a minor seep.
Oil tank gauges may stop working: if the moving float arm parts become bent or simply disconnected inside the oil tank. If you cannot fish out the damaged parts for repair using a bent wire hook, your oil heating technician will probably leave the old gauge parts in the bottom of your oil tank and install a new gauge, hoping the new gauge float won't foul and jam up in the old parts on the tank bottom.
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?
Your oil company can provide a stick, a folding rule, or even a string and weight that can be placed into an oil tank to locate the bottom of the tank and to determine the level of oil in the tank.
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.
How accurate are oil tank gauges
A heating oil tank gauge does a fine job of tellling 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:
When oil is at the top of the tank we know the tank is full. If we know (or calculate) the tank size or volume we know how much oil we have. Usually the oil company already knows your oil tank size - just ask them.
When heating oil is at the bottom of the tank we know we don't have a bit - accurate but troublesome.
When heating oil is exactly in the middle of a square, round, or oval shaped oil tank we indeed have an accurate measurement at this point.
Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website
Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
Additional technical contributors & reference sources for this article are listed below.
Thanks to Alan Carson and Bob Dunlop, Carson Dunlop, Associates, Toronto, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education, publications, report writing materials, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
Critique, contributions wanted: Contact Us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building design, inspection, and repair, and about indoor environment testing, diagnosis, and cleanup are at the InspectAPedia Bookstore.
More Information on Building Diagnostic Inspections and Repairs
Oil Tanks - The Oil Storage Tank Information Website: Buried or Above Ground Oil Tank Inspection, Testing, Cleanup, Abandonment of Oil Tanks
Abandon a Buried Oil Tank, How To - Abandoning Commercial Underground Tanks, Russ Brauksieck, ASHI Tech. Journal, Vol.3 No.1 Spring 1993, P. 40-41 [Reprint]
Petroleum Bulk Storage J. Sibblies, NY State DEC, Advice to Home Owners and Home Inspectors about Oil Storage Tanks - summary from ASHI Chapter Seminar.
Septic Tank inspection, testing, diagnosis, repair
OIL TANK FAILURE CAUSES - Oil Tank Failure Causes - oil tank leaks are caused by corrosion, damage, soil conditions, other factors
TANK FAILURE RATES - Oil Tank Failure Rates - Oil Tank Leak Probability as a Function of Tank Age, Location, Condition, Soil Conditions and Other Factors
OIL TANK TESTING - - How Oil Tanks are Tested for Evidence Leaks, of Current or Previous Oil Spills
National Association of Oil Heat Service Managers, PO Box 380, Elmwood Park, NJ 07407
"Homeowners Guide to Fuel Storage," Agway Energy Products, Verbank, NY, November 1990
Web Link Exchange: Contact Us to list your website or contact information for oil tank testing, tank corrosion research, oil industry experts
InspectAPedia® Home & Site Map - Building & Environmental Inspection, Testing, Diagnosis, Repair, & Problem Prevention Advice: In-depth research & advice on diagnosing, testing, correcting, & preventing building defects & indoor environmental hazards. Unbiased information, no conflicts of interest.
The Mold Information Center: What to Do About Mold in Buildings, When and How to Inspect for Mold, Clean Up Mold, or Avoid Mold Problems
Environmental Inspection, Testing, & Diagnosis On-Site IAQ, Gas, Air Testing, Mold Investigation, Sick Building Diagnosis, Lab Services, & Remediation Plan Preparation - indoor air quality testing, problem source determination, supporting lab work, written remediation plan addressing removal of environmental and other hazards and prevention of their recurrence.
InspectAPedia ® Home & Site Map 
Home Inspection Report Language Library: Buried Oil Tanks, Basic home buyer advice - home inspection report language suggestions
InspectAPedia® Home & Site Map - Building & Environmental Inspection, Testing, Diagnosis, Repair, & Problem Prevention Advice: In-depth research & advice on diagnosing, testing, correcting, & preventing building defects & indoor environmental hazards. Unbiased information, no conflicts of interest. 
