Isn't burning through 75 gallons of oil in three weeks a little excessive for just a water heater?

Question

We weren't even here for two of the three weeks (on vacation), so there was no one even using the hot water.

Answer 1

Yes.

You can try turning down the temperature, but even on the highest setting 25 gals/week is absurd.  You may have a leak in your tank or in one of the lines.

Call your oil company and they'll inspect.

If you have an underground tank it's bad news.

Answer 2

One gallon of Heating oil has 13,690 btus.

1 btu will raise one pound of water 1 degree F

If your incoming water is at 40 degrees F and your Outlet temperature is at 140 degrees F that is 100 degrees of temperature rise.

That means 137 pounds of water. There are 8.36 pounds per gallon of water.

That means for each gallon of oil you should  get 16.4 gallons of hot water (+100) --  (or 1,228 gallons of hot water for 75 gallons of oil).

That equates to about 81 dishwasher or clothes washer loads, or bathtub fills, or showers.

If your incoming water is warmer, then you should get more gallons of hot water.

Either your oil burner is out of adjustment, (burning too rich) or you have a tank leak.

Answer 3

GREAT HORNY TOADS!

That's a lot of oil.  It does sound excessive.  If you own it, call somebody.  That can't be correct.

Answer 4

Are you sure that none of your oil has been stolon