Hello I have questions concerning the Vu-Flow spin down sediment filter 1.5". The written instructions gives different installation, one says install before the pressure tank and the illustration shows it placed after the tank.

My system is set up this way presently. submersible Well pump, shutoff (metal), backflow valve (metal), 4 " steel T pipe with pressure switch and pressure gauge on top connected by nipple, front drain cock. PVC Pipe from T connect to pressure tank, T output to PVC main line which runs about 50 ft. to house than PEX manifold.

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Your description is somewhat cryptic, but the filter should be on the pipe going to the house. From your description, that could be before the tee where the water branches to the tank and house, or after the tee as it goes to the house. If it were on the short run to the storage tank, the water would flow both ways through it depending on the relative pressures.

I always place my filters after the tank, you don't want anything between the pump and pressure switch that could possibly block the flow i.e. a clogged filter.