need help determining height for elevated tank

[kahlilj]

i plan to install an above-ground, lube oil storage tank. the client wants this tank to be elevated high enough to tie into an existing oil header line without using a pump (i.e. gravity-fed).

The planned setup is: a 2000 gallon tank will be located outside; approximately 40 feet of 1" diameter piping will be used to connect to the existing oil line; tie-in to the existing 1" diameter oil line is ~2 feet above grade; Current oil consumption (flow rate) is a maximumn of 8 gallons per day; the oil used has a density is 7.3 lbs/gallon; assume coldest temp will be ~50-60°F;

I tried sizing the minimum elevation for gravity fed flow using bernoulli's equation. i assumed energy equilibrium with current setup (55 gal drum tank on an elevated stand) and came up with an elevation which does not seem right to me - ~3 feet. the Eqn i used was:

p1÷rho + v1÷2gc + z1 + hA = p2÷rho + v2÷2gc + z2 + hE + hf

assumed:
p1÷rho = p2÷rho (both tanks are @ atmospheric pressure)
hE = 0 (because there is no pump involved)

then determined hF =0.3 ft and solved for z2.

should i have made one side of the eqn = 0 and then solved for z2?

can someone direct me to steps in determining what the minimum tank height should be?