well hook-up

If I hook the supply line from my well to a T fitting, with one side to barn and the other side to house will turning on the water in barn cause backflow (siphon) from house? If so , would a one way check valve in the line between the T and the house filter be needed.? I don't want to backflow water thru my softener or house filter.
Thanks

there should be a check valved installed on either side of the tee.

check valve

Thank you for the info...I'll do it!

You don't say where the pressure tank and switch is.

If it/they, they have to be together, are at the well, then no problem and you don't need any additional check valve(s), and you shouldn't have any, except the foot valve for a jet pump or the check valve in/on the outlet of all submersible pumps.

Any additional check valves will hide leaks from it back to the foot/check valve in the well. That is not a good thing and could cost the loss of a submersible pump, contaminated water, other water quality problems, etc..

IF the pressure tank is at one building or the other, the only way to do this correctly is to plumb from the well to the pressure tank and then past the tank, tee off to the other building.

If you don't then water must flow backwards from the tank to the other building when the pump is off, and then reverse back to the tank when the pump comes on which causes water hammer which can damage pumps, plumbing, fixtures and appliances.