By all means use gravity. Plumb it so the bottom of the elevated tank (feed tank) is about 6-12" above the pre heater coils and have that about 6-12" above the float box. Going much higher can cause too much pressure on the float valve and it my not control the level in the pan. Some valves can handle more but many can't, all will work with the numbers I gave you. Also, don't make the feed tank too tall as this can also over pressure the same valve. Then, pump the sap if necessary up to the feed tank. I also like to have a site gage in the line coming from the feed tank. I do this with a Tee, and then go to clear vinyl up and back into the feed tank (sometimes when the valve from the feed tank is opened there is a surge and you will shoot sap up higher than the top of the feed tank, this saves that sap). Now run to the preheater and then the float box. Try to maintain a downward slope all the way, feed the sap in the top of the preheater and out the bottom, then to the float box/vlve. It is sometimes a good idea to have a vent at the top of the preheater to get air out. For a good idea on preheater design I suggest you look at the pictures fellow member Johnny Cuervo has on his site. He can adjust the temperature in the preheater. Most of all, have fun.
You never know, 1 gal. this year, 10 next and then in a few you will have a large sugarhouse, reverse osmosis and vacuum. Then you'll be making several hundred gallons. This is addictive!!!
Dave Klish, I recently bought a 2x6 wood fired evaporator from A&A Sheet Metal which I will be converting to oil fired
Now have solar, 2x6 finish pan, 5 bank 7x7 filter press, large water jacketed bottler, and tankless water heater.
Recently bought another Gingerich RO, this one was a 125, but a second membrane was added thus is a 250, like I had.
After running a 2x3, a 2x6, 3x8 tapping from 79 taps up to 1320 all woodfired, now I'm going to a 2x6 oil fired and a 200-425 taps.