Photograph of a seepage leak at an oil tank filler pipe, wrapped with a rag Leaky Oil Tank Gauge Repair Procedures
How to Fix a leaky oil storage tank indicator gauge in 7 easy steps

  • OIL TANK GAUGE LEAK REPAIR - CONTENTS: What causes leaks at oil tank gauge & how can a leak at or around the tank gauge be stopped? Leaks at the oil tank gauge vial may be due to a faulty gauge vial gasket that is easily replaced.
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Oil tank leaks at the tank gauge:

This article discusses the causes of leaks at oil tank level indicating gauge. While a broken or missing gauge cover can cause leaks, a more common and easily diagnosed and repaired leak point is at the little gasket that seals the oil tank gauge sight glass or plastic cover in its mounting base. This article describes how to diagnose and fix a leak at the oil tank gauge by making or buying a new gauge cover gasket.

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Diagnose & repair leaks at the oil storage tank gauge

Leak at oil tank gauge wets side of oil tank and creates a smelly house (C) Daniel Friedman Oil tank fill or vent pipe seepage leak stopgap repair (C) Daniel Friedman

[Click to enlarge any image]

Leaks around the oil tank gauge or at the gage cover, properly called the oil tank gauge vial, can stink up the building, cause a costly oil tank leak and cleanup bill, and can be mistaken for oil tank piping leaks. Here we explain a common cause and cure for leaks around the oil tank gauge or gauge vial.

Separately at OIL FILL / VENT PIPE SMALL LEAK REPAIR we cited a leak around at the oil tank vent pipe (above left) that actually was ultimately traced to a leak at the oil tank level gauge. A temporary repair of this small leak was to control the oil seepage with a rag so that it wouldn't wet the whole side of the oil tank (above right). Without the rag oil seeping out during an oil tank fill-up wet both sides of the oil tank and stank up the garage where the oil tank was located.

By cleaning the area around the piping, tank top and gauge very thoroughly and then inspecting the oil tank during and after an oil delivery it was apparent that the leak was not at the threads mounting the gauge and vent pipe assembly but rather the leak was coming out of the oil tank gauge assembly. Here are the steps in diagnosing and repairing a leaky oil tank level gauge.

Step 1: clean all heating oil off of the oil storage tank around the apparent leak source. I used a common household cleaner spray and pape towels. Alcohol can also help clean surfaces more thoroughly but it wasn't necessary here. Lacquer thinner or acetone will also remove traces of oil but these solvents will also remove paint from the oil tank and they're more dangerous to work-with.

Clean all heating oil from the oil storage tank surfaces to diagnose the exact leak point (C) Daniel Friedman

Step 2: remove the oil tank filler gauge plastic cover and clean and inspect those parts. Then put the gauge cover back in place.

Remove the plastic oil tank gauge cover (C) Daniel Friedman

Clean around the oil tank gauge cover thoroughly - if necessary you can remove the gauge cover to wipe the surface around the gauge cover mount, then replace the gauge cover and go to step 3. Or if you see a problem with the gauge gasket during this Step 2, jump to Step 4 below.

Sometimes simply hand-tightening the oil tank gauge cover will be enough to stop a leak there - or maybe not as you'll read below.

Step 3: check for seepage at the next oil tank fill-up. If I didn't see trouble in and around the gauge I'd reassemble everything and watch what happens during the next oil fill.

At the next oil fill I asked the driver to be particularly careful not to over-fill the tank (the tank alarm doesn't work on this oil tank so the driver has to listen at the tank vent). Below you can see a wet area around the oil tank gauge that tells me where the heating oil was about to leak from the tank at the fill-up. At below left you can see the oil delivery driver (Bottini Oil, Poughkeepsie, New York) listening carefully to detect just when the indoor oil tank has filled.

Oil delivery driver listening for a full oil tank to avoid spillage (C) Daniel Friedman Evidence of leakage around the oil tank gauge (C) Daniel Friedman

At above right you can see a little heating oil seepage around the oil tank gauge vial mount that we discuss next. Had the Bottini oil company driver not stopped filling the tank when he did there would have been a bigger leak.

Step 4. Spot the point of origin of the oil tank piping leak: in this case it was at the oil tank filler gauge. Check for a damaged or missing oil tank gauge gasket. Looking with care at the rubber gasket in the oil tank gauge mounting opening it was obvious that this was the trouble: the gasket was worn and incomplete.

Watch out: leaks will also occur around an oil tank gauge if the plastic gauge cover is missing entirely or if the gauge cover base is cracked or uneven such that it can't depess and seal the gauge gasket inside the mounting opening. In that case you'll need to replace the gauge cover assembly entirely.

Damaged oil tank gauge gasket causes leaks (C) Daniel Friedman

Step 5: Obtain or make a replacement for the leaky oil tank gauge gasket. This little gasket (see below) was more than 40 years old and had done yoeman work for decades. A small pair of needle-nose pliers helped remove the old gasket for inspection. It was time for a new oil tank gauge gasket. A stop at your oil heat parts company to ask for the gaseket might be successful, but as I had some rubber roofing material on-hand it was trivial to cut out a new, more substantial gasket. We'll see how well rubber roofing stands up to home heating oil.

How to make a replacement oil tank gauge gasket (C) Daniel Friedman How to make a replacement oil tank gauge gasket (C) Daniel Friedman

Youy can see the new home-made oil tank gauge gasket at above right. Since the center of the gasket has only to clear the small wire rod of the oil tank level gauge and big enough to slip over the gauge indicator disc, I decided to make this gasket wider and more substantial than the original gasket. The outer perimeter of the gasket must be well rounded to fit neatly and without leaking into the oil tank gauge sight glass cover base but the inner perimeter can be a bit more crude. [Click to enlarge any image]

Step 6: Install the new oil tank gauge cover gasket to stop leaks at the oil tank gauge

How to install the new gasket on the oil tank gauge to stop leaks (C) Daniel Friedman How to install the new gasket on the oil tank gauge to stop leaks (C) Daniel Friedman

You can see the do-it-yourself oil tank gauge cover gasket slipping over the oil tank gauge (above-left, take care not to bend the gauge rod) and then placed into the mounting well of the oil tank gauge cover (above right). I made the gasket just slightly oversized - about 1-2 mm - figuring that it would compress into place when I screwed in the gauge cover and I'd be more sure it'd seal well.

Step 7: Replace the Oil Tank Gauge Sight "Glass" - actually it's plastic - by screwing it snugly in place. Don't over-tighten or you may break the cover. Hand-tight is enough. No pipe wrenches please.

Oil tank gauge cover back in place (C) Daniel Friedman

Step 8: Monitor your oil tank gauge leak repair: be sure that the gauge is not leaking by checking it again at the next oil tank fill-up.

Oil tank gauge inspection for leaks (C) Daniel Friedman

Above is the repaired oil tank gauge in place a year after the gasket repair that we described. So far, after several oil tank re-fills, there is no seepage around the gauge.

If thees oil tank fill and vent pipes have not already caused a costly oil spill outside the building it's due to luck and the fact that oil tank filling does not expose the tank to extreme pressures. Also

A better design would have either provided for drainage of the well through which these oil tank pipes pass or it would have sealed them entirely to protect the piping from standing water - or worse, standing salty water.

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