Oil Tank Question

[Brandon Whitmore]

The data plate on the exterior oil tank I inspected today said "interior storage tank" on the data plate. Are some oil tanks only supposed to be used on the interior?

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[Jim Morrison]

That looks like a pretty old plate from a pretty old tank. I doubt that being inside or outside has a big impact on the longevity of the tank, though. Still, if it's old and not installed as intended, I think it's worth telling your client it's old and improperly installed and could leak and have to be replaced without notice.

A 12 gauge steel tank in the Boston area will generally last 50+ years in my experience.

[Brandon Whitmore]

Thanks for the response Jim.

Based on the data plate, would you say it's safe to assume that the tank was not meant for use outdoors? I'm not sure if I've just never paid this close of attention to data plates on oil tanks (don't see them often), or if tanks don't usually indicate this.

The entire 4k sq. ft. 100 yr. old house was moved to this site about 10 years ago. It's possible that this tank has only been installed outdoors for the last 10. The paint was peeling and the exterior was pretty rusty.

[Bill Kibbel]

The data plate on the exterior oil tank I inspected today said "interior storage tank" on the data plate. Are some oil tanks only supposed to be used on the interior?

That's correct. A large majority of above ground, outdoor tanks installed were not manufactured or listed for outdoor use.

Corrosion is pretty far down the list of problems with fuel oil tanks located outdoors.

[hausdok]

Yeah,

They don't rust from the outside in anyway. They rust from the inside out where the water sits under the oil on the bottom of the tank.

ONE TEAM - ONE FIGHT!!!

Mike

[Jim Katen]

I've never thought to read the labels on old oil tanks. Never seen or heard of one rusting from the outside in though. Like Mike said, they usually rust from the inside out.

[Brandon Whitmore]

They don't rust from the outside in anyway. They rust from the inside out where the water sits under the oil on the bottom of the tank.

I figure if it rusts from both the inside and outside, the rust will meet up and a leak will spring more quickly...

If rust isn't the concern with using an interior unit on the outside, then what is the big issue(s)?

[Brandon Whitmore]

Corrosion is pretty far down the list of problems with fuel oil tanks located outdoors.

Bill,

What are some of the other issues?

[Jim Katen]

They don't rust from the outside in anyway. They rust from the inside out where the water sits under the oil on the bottom of the tank.

I figure if it rusts from both the inside and outside, the rust will meet up and a leak will spring more quickly...

If rust isn't the concern with using an interior unit on the outside, then what is the big issue(s)?

The things I always look for are decent footings and seismic support. I can't remember having ever found a leaking above-ground tank. But that's probably because the leaking ones were obvious and got replaced before I got there.

I do remember a large above-ground oil tank in Laurelwood, though. It was on a farm and was located next to a large barn. It didn't have any fuel lines leading to it, just a spigot, so I figured it was for diesel fuel. Oddly enough, the spigot was all crapped up with some kind of nasty, sticky, black stuff. So, of course, I tasted it. . . . molasses. Turns out that they added it to the cattle's feed.

[John Kogel]

Corrosion is pretty far down the list of problems with fuel oil tanks located outdoors.

Bill,

What are some of the other issues?

Worst case scenario, I would think: A chronic leak that is ignored, so it drips long enough to contaminate the soil behind the house.

Around here, the insurance people don't like to see an indoor tank, so they are becoming rare. As a rule, oil tanks need to be inspected, usually by someone sent out by the oil supplier, every ten years.

[Brandon Whitmore]

The things I always look for are decent footings and seismic support. I can't remember having ever found a leaking above-ground tank. But that's probably because the leaking ones were obvious and got replaced before I got there.

This one had decent footings from what I could feel, but they were buried a good 12" down so it's tough to say for sure. I use a 2' long screwdriver to probe, which I use to check pier pad depth at deck pads, etc.

Thetank was overgrown by large rhododendrons. I had to claw my way through just to get a peek at the tank. Does dense vegetation qualify as part of a seismic restraint system......

[Rob Amaral]

I had an outdoor tank (under a little shed roof) leaking at the top due to chronic drip-drip-dripping from a little 'roof leak'.. nasty..

Don't downplay 'fuel oil on the floor' in an old house. I had one last year that leaked into the basement of the house next door.. "Major"..

It's worth checking the gauge of the steel.. one of our guys found one of the wrong gauge and it leaked within a month of the inspection. He warned them to replace it..

Don't assume anything with fuel oil tanks.. I found another 'new' (7year old) tank leaking at a pinhole in the steel... you have to check them with focus and as much as possible...

[John Kogel]

This 8 year old tank in great shape was leaking from a loose fitting. Old folks tend to let things go.

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[Jim Morrison]

Other problems with outdoor tanks:

The oil is much colder. Oil will congeal at about 10 degrees F, which will clog the 3/8 inch copper tube between the tank and the burner and shut the heat off completely. We get those temps at least once annually here in Boston. When oil is very cold but not congealed, the conical shaped spray at ignition can collapse and is much louder than normal.

[Bill Kibbel]

Corrosion is pretty far down the list of problems with fuel oil tanks located outdoors.

Bill,

What are some of the other issues?

At just above 20°, the paraffin in #2 fuel oil "congeals" causing an inefficient, unreliable burn. Aeration of the fuel is another problem. You're not supposed to have a bottom feed valve on any exterior tank, however when almost all heating equip. is in the basement around here, that's where it is on most tanks. I've also been told that tanks in unconditioned spaces are more likely to have water accumulate in the bottom of the tank.

[Brandon Whitmore]

Thanks Bill and Jim. Temp's aren't really something we have to worry about around here, at least not all too often. Then again, when the temp. drops that low (once every 10 years or so?), that's when someone really needs that heat to work well.

[hausdok]

Around here 99.999% of those things are outside below ground, so I've never had a chance to read any of the labeling on one.

ONE TEAM - ONE FIGHT!!!

Mike

[Brandon Whitmore]

Around here 99.999% of those things are outside below ground, so I've never had a chance to read any of the labeling on one.

I don't see many above ground tanks any more, and a much larger percentage are buried here as well.

Maybe you'd better dig up the UST's from now on to make sure they're approved for direct burial......

On another note...... I inspected a house a month ago, and found a couple of unused copper lines that ran within about 10' of the furnace that were cut off and folded up in the floor joists. The selling side refused to believe (imagine that) there was ever a tank on the property, and the buyer didn't want to pay for a tank locate company to come out.

The buyer's agent refused to let it go and paid for a tank locate herself just for piece of mind. Now, the seller is in the process of not only decommissioning a tank, but having contaminated soils dealt with. Turns out the tank was located beneath a large deck, and the contaminated soil worked it's way into the crawlspace. Sounds like the clean up is costing upwards of 10k.

How nobody ran into that tank I'll never know. It sounds like it was pretty close to the edge of one of the addition's footings.

[Marc]

Around here 99.999% of those things are outside below ground, so I've never had a chance to read any of the labeling on one.

I don't see many above ground tanks any more, and a much larger percentage are buried here as well.

Maybe you'd better dig up the UST's from now on to make sure they're approved for direct burial......

On another note...... I inspected a house a month ago, and found a couple of unused copper lines that ran within about 10' of the furnace that were cut off and folded up in the floor joists. The selling side refused to believe (imagine that) there was ever a tank on the property, and the buyer didn't want to pay for a tank locate company to come out.

The buyer's agent refused to let it go and paid for a tank locate herself just for piece of mind. Now, the seller is in the process of not only decommissioning a tank, but having contaminated soils dealt with. Turns out the tank was located beneath a large deck, and the contaminated soil worked it's way into the crawlspace. Sounds like the clean up is costing upwards of 10k.

How nobody ran into that tank I'll never know. It sounds like it was pretty close to the edge of one of the addition's footings.

Title me Mr. Drift if you wish but we don't get oil tanks here. Don't use oil for heating. What I do see here, mostly in a specific old part of town, is abandoned septic tanks beneath an addition to the house. They're steel and they're forgotten, at least by the owners who built the additions over them. When they rust out and collapse, rainwater that enters the crawlspace drains out via these old tanks because they're still connected to the muni septic lines.

One such house last year had a crawlspace that looked like a miniature version of the Grand Canyon. Several piers had collapsed into the eroded 'canyons'. I didn't try to get into the tank but there would've been enough height for me to stand up. The open crawl itself was only about 2'.

Marc

[John Kogel]

Marc, I'm trying to picture you standing in a septic tank in a crawlspace. Would you wear boots for that? Hipwaders? []

Regional differences are interesting. In my area, buried oil tanks are no longer allowed. They rust out and leak in this climate. Most of the old tanks have been found and decommissioned or removed. There is a tank service contractor that will come out and do a free search for a buried tank, so if it is a pre-70's house in town, I recommend a tank search. Nobody wants to discover an old abandoned and leaking tank in their yard. If it's not leaking, it can be filled with sand. I've encountered a few of those.

The two lines are a good clue. Above ground tanks don't usually need a pump return line, but the buried tanks generally do. However, I have seen where a buried tank in the front yard had enough elevation to supply the basement furnace by gravity, so that's no definite indicator. That one had a single copper line to the furnace, pinched off. The tank breather pipe coming out of the ground at the corner of the house gave it away. The filler cap was buried.