What would be the best way to hook up two houses to a single 3000 gallon cistern?

Question

I have a 3000 gallon (11 m³) cistern that is being filled by a 15 gallon (57 litre) a minute pump 900 ft (275 metre) down. I have a pump house that has a pressure tank in it now that feeds my house, but I want to take water to a second building 600 ft (180 metre) away. There is a 1" (2.5 cm) line in the ground to the second property. I would like to put one pump from the cistern to feed both houses if possible. What's the best way to go about this?

Answer 1

I'm not saying this is the "best way", but it's a way, and it has the advantage of being simple and inexpensive.

The calculated pressure drop through 600 feet of new smooth 1" poly pipe (1.06" ID) with no joints or fittings and with water flowing at 5 GPM is 4.25 psi. Bearing this in mind, if the 2nd house is not doing large scale irrigation, you can consider using just a check valve and pressure tank at the 2nd house without an additional pump.

The 1st house's pump, pressure switch and pressure tank will keep the 2nd house's tank supplied.

When the 2nd house's water is used, pressure in its tank will drop. When its pressure falls below the 1st house's current tank pressure minus the check valve's differential pressure, water will start flowing into the 2nd house's tank. When and if this causes the 1st house's tank pressure to fall below its pressure switch's "ON" pressure, the 1st house's pump will turn on until pressure is restored and reaches its "OFF" pressure.

When no water is being used in the 2nd house, its tank will come to equilibrium with the 1st house's pressure, minus the check valve's differential pressure.

Why not skip the pressure tank in the second house? There may be times when usage is high for a short period, so it's nice to have the capacity to provide high flow without relying on make-up from 600 feet away.

If the current pressure switch setting is good, perhaps set it 5 psi higher so the 2nd house will experience the same goodness after the minor pressure drop from the long run of pipe during flow, plus the loss from the check valve.

The check valve is to prevent water, once delivered to the 2nd house, from flowing back to the 1st house when they use water.