oil tanks not drawing properly

zepfan

I have a customer with two 250 gallon oil tanks in their basement, they supply oil to one 200 mbh boiler.One pipe system with no return to the tanks. The supply from the tanks are manifolded together then run over to the boiler. The tank's vents are manifolded together then run outside the home through one pipe. Each tank has their own fill line, that runs outside. The issue is is that the tanks never seem to draw down at the same rate. The one that is closest to the burner always seems to get to 1/4 full before any oil is drawn down from the other tank. Both tank floats were replaced last year, and I checked them today to make sure they were still in working order. The tanks are located side by side, and both are level front to back. Like I had mentioned the other tank will eventually drawn down, however I would think that the way they are piped with one common line to the boiler that they would both drawn down at the same rate. Any ideas or suggestions as to why this is happening would be much appreciated. thanks to all.

STEVEusaPA

If the supplies are coming out the top:
The depth of each fill pipe must be the same in the tank. The overall length from inside the tank up to where the tee together needs to be the same (actually should be, not has to be).
If that is correct, then either a pinhole in a supply tube in the tank or a blockage would be your problem.

If the supplies are teed and coming out the bottom, then one side has a blockage/partial blockage. Hopefully the oil line is piped in such a way that with minimal disconnection you can blow it back (with a hand pump only), re-connect, bleed.

I'd also see if the driver can fill that tank that draws down faster first.

If it's really bad, treating the tank and maybe even cleaning the tanks may be in order.

I had a problem with 2 external tanks, tied together at bottom, but feeding out the top. Due to their old age, sludge/water staying on the bottom, and their inability to want to do anything about it, every time it got below freezing, the bottom connection froze, oil pumped out of one tank only, and they ran out of fuel, sometimes with the other tank completely full.

EBEBRATT-Ed

what @SteveusaPA said

zepfan

Thanks for the response. The supply to the boiler comes out the bottom of the tanks, and the fills out of the top