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Minimum safe tank thickness

dh1989 Member Posts: 22
I purchased an ultrasonic thickness tester to sound my 275 gal basement oil tank. I checked the bottom seam and am reading 2.1 mm. Top of the tank reads 2.2mm. House was built in 1968 and I'm not sure if the tank is original.

I assume this is a 14 ga tank. What is my minimum safe thickness before I need to worry about replacement?



  • Zman
    Zman Member Posts: 7,572
    It sure looks like you are close to spec.


    How accurate do you think the tester is. Is it effected by the oil?

    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • dh1989
    dh1989 Member Posts: 22
    Supposedly accurate to .1mm. Not sure if the oil affects it in any way. The tank is about 1/8 full and I took readings all over.
  • icesailor
    icesailor Member Posts: 7,265
    If its an indoor tank, in a reasonably warm place, its probably a 45+ year old original tank.

    How much did the thickness tester cost? More than a new tank?

    Some jurisdictions require a tank that old be replaced. Whether it leaks or not.

    IME, tanks don't leak like you think. They either develop a rust spot "pimple" around the bottom, or start weeping on a seam or weld. In 1968, about anyone could build and sell residential oil tanks. By the 1980's, few were because of more stringent regulations and insurance issues. There were some really cheap and bogus tanks out there. Not now.
  • dh1989
    dh1989 Member Posts: 22
    Tester was $100. It's a chinese one but I calibrated it and tested it on various pieces of sheet metal I checked with calipers. Appears to be accurate.

    Tank has some light surface rust. The only leakage I see is an old sticky stain from what looks like spillover from the vent connection (overfilled in the past?). It's not an active leak as everything has been dry since I filled the tank back in November.

    Tank: http://s1.postimg.org/v0ms0obfj/IMG_3727.jpg
    Bottom: http://s21.postimg.org/ly9ee0ow7/IMG_3724.jpg
    Outlet: http://s2.postimg.org/xbfboaecp/IMG_3725.jpg

    Just some cobwebs underneath and some dried oil from the old vent leak. Cleaned the surface with a paper towel before I sounded it and I didn't see any 'pimples' or questionable areas.

    Looks like a 60s era tank?
  • DocTM
    DocTM Member Posts: 1
    For a standard fuel tank in your basement or garage; I have one forty years old and I wonder what’s the standard thickness of the tank?
    EBEBRATT-Ed Member Posts: 15,605
    12-gauge steel I believe. Some older ones were 14 gauge and I have herd they were 16 gauge in the old days. Don't know if that is true. It should say on the name tag what it is made of and thickness. 12 gauge =0.105"
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 8,022
    I remember purchasing oil tanks when you needed to specify if it was going to be used indoors or outdoors. You could get away with a UL listed 14 gauge tank in the basement. Outdoor tanks must be 12 Gauge.

    Does anyone even make 14 gauge tanks anymore?

    Edward Young Retired

    After you make that expensive repair and you still have the same problem, What will you check next?

    EBEBRATT-Ed Member Posts: 15,605

    Don't think 14 gauge is legal any longer