installing a pressure red. valve and a thermal tank

Well i just purchased a pressure reducing valve and a thermal expansion tank. My question is the house is a side by sided duplex...roughly 3k sq feet..(4 bdrms on each side) will this one tank be enough?.. also can i put the pressure reducing valve on the main line that is running from the floor to the ceiling or should it be installed on the pipes overhead??.. Also any tips ANYONE might have will be greatly appreciated.. this is one of my larger plumbing endeveors...i know to install the p.r.valve in between the main shut off and the thermal tank..Thanks in advance!!

The pressure reducing valve can be anywhere convenient after the main. The size of the expansion tank is determined by the gallon capacity of the WH. The tank should have on it or in the instructions a chart for gallons. If you have 2 WH, base the size on the total, or use 2 expansion tanks.

thanks so much Jimbo.... can i install the p.r.v. parallel to the walls or does it have to be paralled to the floor... or does it matter???