Home heating oil tank -- Which pipe to fill? Actually do need answer fast

I am the proud owner of an empty home heating oil tank and I need to drop in a few gallons of diesel to tide me over till tomorrow’s delivery.

The problem is I have two pipes sticking up next to each other with no indication which is the fill pipe and which is the vent pipe.

Pipe A is a 2 inch pipe with a cap loosely screwed on.

Pipe B is a 1.5 inch pipe with an over-sized cap placed on top. Only gravity is keeping the cap in place. If I follow Pipe B to the tank, the Empty/Full valve thingy is attached where Pipe B goes into the tank.

So… which pipe is which? And what will happen if I pour diesel down the vent pipe by accident?

Any guidance would be appreciated as I’d like to fill this thing before the pilot light goes out. Thanks in advance!

From every indication that I see, the fill pipe should be the one closest to the end of the tank and it should be the screw-on cap. The vent pipe will be towards the center with a loose-fitting cap.

But I’ll let someone with an actual oil tank confirm this.

The larger one, but the smaller one can also be used if needed, it’s just a pipe into the tank.

I’ve never seen an oil burner with a pilot light. They typically use an electrically-powered igniter, roughly comparable to a spark plug.

I can’t recall seeing a oil tank vent that was capped. They normally have a screen to keep out bugs. Sometimes they use a elbow to turn it and keep out rain.

Capping the vent doesn’t make sense. Unless the tank isn’t being used. An old tank needs to be pressure tested before filling. Oil leaks are an environmentally hazard and really expensive to clean up.

ok, this photo is how I remember how it was at my parents house.

The fill line is directly over the tank. The vent is off to the side against the wall. The vent is turned down so water doesn’t drip in. There should be a screen on it but can’t tell in the pic.

The larger 2" pipe is the fill pipe. The smaller one has a whistle in it at the tank which would reduce fuel going in the tank.

Thanks, everyone. I put the diesel in the 2" pipe and everything seems to be going fine.

Xema, thanks for that info. You can tell I’m not all that familiar with oil heat. I guess that’s another reason my heat doesn’t work when the power is out.

Aceplace57, the smaller pipe has a loose cap on it, I guess to keep out rain. I’m pretty sure the guy takes it off when he is filling the tank. It would be pretty apparent if the tank starts leaking as it would be all over the basement.