Plumbing – How to boost water pressure from the city main up a long hill

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The city has pulled a water line down the road so I can now stop getting water delivered if I can figure out how. The problem is that my house is about 700ft up a 200ft hill. The city pressure goes from 70psi to 0psi about 1/2- 2/3 of the way up the hill. So I need a pressure boost to get to hilltop. Assume I can get power, any booster suggestions?

Best Answer

It's way too soon to be picking products. First you need a strategy.

I see five delivery problems here.

  • Getting enough pressure of water to climb your hill. Rule of thumb, you lose 1/2 PSI per vertical foot (a little high, but you'll need pressure for flow, too.)
  • Getting enough volume of water up the hill for your instantaneous use. Pipe walls have a lot of drag, and you have a lot of pipe walls.
  • Getting electricity down to the pump location. Perhaps ironically there's power right near the pump location, but not on your meter.
  • Getting enough electricity to the pump location to satisfy your instantaneous use. Which could be quite a lot.
  • Reliability of the pressure from the water company. OK it's 70 psi now and so you pick a location 100 feet up the hill, which 70 psi can serve. But what happens when all your neighbors shower at once and it plunges to 35 psi? Your pump goes dry since 35 psi can't push it up 100 feet! Yowch.

So there's no question in my mind that I'd put the booster pump as low as possible. That means both a water and electricity run for the full 700 feet, and that ain't chump change. So when reaching for Franklins, I first reach for a sharp pencil and the the old IBM "THINK" sign.

  • if you size for instantaneous use - abandon the cistern - you have two problems. First, pipes and cords must be sized for worst-case surge, which means they are huge and expensive. (and tempting theft candy). Second, no power = no water.
  • Since the cistern has worked for you, what if you keep it? Surge load is absorbed by the cistern, as it is now, and the pump and piping only need to refill the cistern (keep it topped up). It can do that at a very low rate with fairly small pump, pipe and wires. Still, no power, no water.
  • Since you own land 700 feet wide and 200 feet high, any chance you own higher? Put your cistern up there (like this guy) and let that .433 PSI per vertical foot supply your water pressure. Now you're showering with no power! Also handy for firefighting, something to think about when sizing your cistern. Now your pump down low has to push even higher, but again only a trickle, just to top up the cistern.

Honestly, you have to price it all ways and decide which features you want.

So suppose you want a cistern system that can recover 240 gallons/day (seems like a lot.) That's 10 gallons per hour. 10 gallons weighs x8.3= 83 pounds. If you are lifting 200 ft, that is 83x200=16600 foot-pounds per hour of energy. 1 KWH is 2655220 ft-lbs., so this will take you .00625 kilowatt-hours per hour, or 6.25 watts. That has "solar" written all over it - derate 80% for solar availability (lifting 50 GPH 20% of the time) and you're still at 31 watts. Easy peasy.

If we wanted a surge/demand system that could supply 10 GPM, that's 600 GPH, 996000 ft-lbs per hour, 375 watt-hours per hour, assuming 39% pump efficiency, that's about 4 amps at 240V. 12 AWG wire ($479) can do that, but that assumes no friction losses in the pipe, which assumes fat pipe. You'd have to balance the cost of fat pipe vs the cost of thicker wire to pump up thinner pipe. That balance is above my skill level. Normally I'm all about conduit, but in this case I'd direct-bury the electrical cable so it isn't stolen.

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