how high

[deere_jennings]

what is the minimum height for a head tank to be above a preheater? will it need to be above the highest part of the preheater or just the inlet?

[johnallin]

Unless you can put a bypass in; the bottom of your tank should be higher than the highest part of your preheater. If not; sap will stop flowing up into the preheater when the level in the tank drops below the highest part of the preheater. Not a good thing - as you're no longer feeding your flue pan! My tank is not quite high enough, so I put a bypass in to direct the remaining sap in my tank straight into my float box on the flue pan.

[maple flats]

I have the bottom of my head tank at least 8-10" above the high point on my pre-heater. I have vents on each end of my manifolds in the pre-heater to vent in case of an air lock, but I have never needed to vent even once. Thus, I suggest you still have vents, get the 8-10" elevation over the high point on the pre-heater and you should do as well as I do.
I find it good piece of mind to have the vents even though I've never needed to use them. Kind of like fire insurance, you want to have it, but never want to need it.
Would 4" or 6" work, I can't say, maybe but no guaranties.

[Sugarmaker]

At least a few inches above the highest point on the preheater should work. Not much magic here.
Regards,
Chris

[deere_jennings]

thanks for the help guy. had trouble getting the height I need in the sack without cut more holes in ceiling. my head tank is a 275 tote. I cut a 1/3 off and got more height. plus a lot easier to clean and move. got 5" above preheater now hope the will work