I am replacing my waterboss big boss and thinking to get a fleck 5600. There are 2 people in our house and our water tests 11 hardness, iron is 1.5, ph 7 . I have 3/4 pipe going into and out of the waterboss with quick disconnect hose . I need to know sizing recommendations and where would be the best web seller to purchase from. I'm going to try to do the install myself so I will probably need support from the seller.