Petrometer reading vs. empty fuel tank.

radonc

In ground tank = 1080 gallons (48” dia)
Petrometer model = 1329

In 2007 I had some issues with the in-ground tank. Busted up the concrete and dug down 22-1/2” to top of tank. The black iron pipe used for supply and return were corroded.

There are three taps. One is used for vent and stick measurement, the middle one, 22” from the stick tap is used for supply and return with a double tap, the third, 22” from that has the petrometer copper tubing line. There is a fill tap that leads out to the sidewalk, but that is probably closer to the end of the tank.

The timing was bad when this happened, lots going on. So I did not have the tank clean. Some companies wanted to cut the tank to have it cleaned, as oppose to just pumping out what’s in there. Anyway, someone pointed out that the tank may have been cut years ago and cleaned.
So, I didn’t want to jeopardize the integrity of the tank.

I opted to have my oil supplier run new lines (1/2” copper tubing) and install a new petrometer.
I wasn’t there when the work was done. But the service techs who did the work told me they will pull the new 1/2” supply pipe several inches off the floor of the tank, above any sludge that may have accumulated over the years.

BTW, when I took out the old supply pipe, it was 3/4” with a foot valve. So they place a 1/2” pipe without a foot valve.

This winter had some water/sludge issue. Hand pump at burner solve it. I decided as soon as the cold weather is over, I’ll pump out the contents of the tank myself.

Got two 55 gallon drums, a 30 gallon drum, a transfer pump (Lowes), my oil tank measuring stick (Home depot). As well as a bunch of 5 gallon buckets.

I also wanted to find out where the supply pipe was located. So I figured I’ll let the burner work (hot water only at this point, since winter is over) until it stops, with a new filter of course.

At 8”=124 gallons, I placed a 6’ pipe with an elbow all the way to the bottom of the tank and pumped out enough to fill three of the 5 gallon buckets. It was oil and sludge mixed in, since I was drawing from the very bottom of the tank. I let those settle for two days and recovered the oil on top and the sludge remained on the bottom of the buckets. This was just backup oil for when the burner stops. Also I wanted to check out the pump.

The burner stopped when the petrometer reading showed 4”=47 gallons. I took my stick and measured the contents of the tank. It showed 4-1/2”. So the petrometer was off by 1/2”.

I now decided to pump out the remainder of the tank. I got about three 5 gallon buckets filled with heavy sludge. Then the pump wouldn’t suck anymore. I checked the petrometer reading and it shows 3-1/2”=40 gallons. But when I measured using the stick it shows about 1/2” of liquid at the bottom. I made sure to pumped the petrometer, but no change
Is the petrometer measuring the full volume of the tank? Shouldn’t it correspond to the stick measurement? I looked at a pdf of the installation of a petrometer and it shows the Air Bell placed to the very bottom. Is this due to the red-x liquid still under pressure in the line?
Is the petrometer measuring from the supply pipe height? I’m wondering if I fill the tank with 100 gallon of oil, will the petrometer equalize with the true depth again.

Any help on this would be appreciated. Wrecking my brain on this one.

EBEBRATT-Ed

The petrometer is probably not working with the oil level that low. Personally we used to keep the oil suction lines 6" up and the return the same from the bottom. Stay away from using foot valves on #2 oil. We only used them on gas tanks. !/2" lines are large enough. Not sure about cutting a tank to clean it never herd of that. That doesn't sound like a good idea to me. You might put some fuel additive or kerosene in the tank to try and dissolve any remaining sludge. How old is the tank? Maybe it's time to yank it. Leave an opening so you can easily stick the tank. You should measure before you order oil. petrometers are ok but can be troublesome

radonc

EBEBRATT-Ed said:

The petrometer is probably not working with the oil level that low. Personally we used to keep the oil suction lines 6" up and the return the same from the bottom. Stay away from using foot valves on #2 oil. We only used them on gas tanks. !/2" lines are large enough. Not sure about cutting a tank to clean it never herd of that. That doesn't sound like a good idea to me. You might put some fuel additive or kerosene in the tank to try and dissolve any remaining sludge. How old is the tank? Maybe it's time to yank it. Leave an opening so you can easily stick the tank. You should measure before you order oil. petrometers are ok but can be troublesome

Thanks.
There seems to be a slight layer of sludge/liquid left on the bottom. I'm thinking of ordering 100 gallons of oil, let that stir up what's left on the bottom, then pump the "soup" mixture out into the two 55 gallon drums. Let the contents of the drums settle for two days with any sludge settling to the bottom of the drums and then recover the good oil on top.

This way I give the bottom of the tank a good wash-out and see if the petrometer reacts to the 100 gallons.

Kerosene is very expensive. I thought about adding 5 gallons to the empty tank and see if that helps in diluting the sludge, then pumping the contents out.

Heating oil prices are about $2/gal now.

again, I measured using a stick, straight down, and it shows less than 1/2" of liquid/sludge, probably along the length of the tank.

SWEI

Pump that "soup" through a 10µ (or finer) spin-on filter.