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Why is there a gallon of oil under my oil tank?

jsflynn603 Member Posts: 1
Now this may seem evident--"you have an oil tank leak," but I don't think this is the case.

I have an old farm house that I plan to retire in, it's nothing that 70 grand won't fix.  It has a working forced air oil fired heating system.  I've replaced the oil tank ~1977, and always use oil conditioner (I can't remember the name but buy it from Webb).

I keep the heat at 40 degrees over the winter and use about 200 gallons each season.  This year I got a fill up.  Yesterday I visited my farmhouse and walking in I knew I had a problem just from the oil smell.  Yup, there's about a gallon of oil on the concrete under the tank.

At first I thought: "oh crap--the tank is leaking," but then... The tank appears dry everyplace.  The filter/outflow pipe and adjacent piping is not leaking.  So....if I have a leak, it's at the "top" of the tank, because it is not leaking now.

One thing I did notice is a small, dark streak of dried oil running down the tank from where the vent pipe is inserted at the top of the tank.  Whoever installed it did use pipe thread sealant but this has obviously leaked in the past.

I'm wondering if the person who filled it overfilled it.  If so, then I imagine that the vent and fill pipe fills up and sprays out the vent.  Yes, the fill person should be standing there listening to the window but that is not always the case.


(A side story...back in 1984 I had a fill-up for an inground 275 ground tank in Keene, NH, and the fill guy managed to pump about 400 gallons into it... Perhaps he was deaf--because he did not react when the whistle stopped.  Perhaps he was blind too, because he managed to miss the oil spouting out of the ground 3 feet away after he blew out the inground fill pipe... yup, 125 gallon of oil at his feet, on the ground.... so, so much for delivery people always being observant...)

In this case I'm wondering if it was overfilled and since my system is shut down (at the valve before the filter) the oil in the vent/fill pipe just sat there slowly leaking out at the base of the fill pipe. 

Does this happen?

Do leaks occur at the top of the tank?  (Because I cannot detect a leak and it's filled.  So if there is a leak, it's at the top few inches.

Actually I'll be rather pleased if it was just over-filled.  A gallon or two of oil on the concrete floor is easy to remedy and I only lose about $4, but now I'm wondering...

And yes, the person who filled it denies overfilling it.

Any thoughts on how to proceed to figure out what the story is?



  • icesailor
    icesailor Member Posts: 7,265

    You very well could have a leak at the pipes coming out of the top of the tank. There also should be a Vent Alarm/whistle that should stop whistling when the oil level in the tank is about 4" from the top. But to have the amount of oil on the floor from a leak doesn't seem possible. Unless the driver is hearing impaired. If there is a whistle installed on the tank, and it isn't whistling, the oil dealer will usually, immediately call you and tell you to get it fixed.

    I recently repaired a recently installed oil Schutz tanks that had more leaks than a poorly made boat. The installer used a Rectorseal pipe thread sealant that is blue. I needed 3' pipe wrenches to get it apart and it leaked. I put it back together using Rectorseal #5 and something that oil guys loos their shorts over but it never leaks and it never, ever leaks for me.
  • Alan Welch
    Alan Welch Member Posts: 270
    try this

    Keeping the heat at 40 degrees you probably haven't run the burner yet. If you can, back out a plug on top of the tank . If the oil is right to the top it was overfilled.   watch for weeping before you fully remove the plug, there may still be some  oil above that point. The whistle stem should stick  into the top of the tank several inches, when the rising oil reaches that point the whistle stops, and so should the oil delivery .
  • Patchogue Phil_2
    Patchogue Phil_2 Member Posts: 304
    edited October 2012
    listening to the window ????

    "the fill person should be standing there listening to the window"

    Are you saying that the vent pipe does NOT exit to the great outdoors?
This discussion has been closed.