Saltwater and Heating Oil

LIBob51

I had a work order yesterday to replace a flood damaged Riello burner in a five year old Peerless WBV-3 boiler. Riello coming out, Riello already set for the boiler going back in, sounded nice and easy. First thing I did was close the fireomatic valve, break the union that connects to the pump, and open the fireomatic again. I was just trying to check the oil flow from the basement tank, and I had fantastic flow, the problem was that I had water flowing out of the tank. I stuck the tank with water finding paste, and found 9 inches of water in the 275 gallon tank, according to my chart that's 53 gallons of water inside the tank. I understand that saltwater is exetremely corrosive, and that water obviously needed to be removed from the oil tank. The customer ended up paying to have the contents of the tank pumped out, both oil and water. I sold and installed a new tank, and raised the fill and vent another 2 and a half feet from where the were on the outside. The thing I'm skeptical about is that I was told saltwater will not separate from the oil and settle at the bottom of the tank like fresh water does. My question is, is that true?