Oil line losing prime

Mark Berry

I have a new customer that has two Dehoust double wall oil tanks piped to one boiler. Since the system was put in, once the tanks get down to 40 percent the oil line loses prime overnight. The installing company has been back several times to repipe and reseal but problem still occurs. I was going to move the filter down to ground level but I wanted some input from someone that has installed these tanks before. I contacted the factory and they told me to get a duplex bushing,but converting to a two pipe system would not work because the tanks can not self-equalize do to top feed. Any thoughts would be helpful.