Newbie with questions... Lift pump for municipal water supply

[DaveK01]

My home requires a lift pump for local municipal water to reach the house. Static water level of the municipal supply is about 60 ft below my house. I need to have around 20 GPM at the house, so need to understand how to evaluate pump curves for the situation.

Next, the existing lift pump system is a 25 GPM, 3 HP Jacuzzi, located within an existing pump-house. The existing pump (so far not the motor) is failing (leaky seals and perhaps worse inside), and the pumphouse (large-size, 8 x 12 ft, don't know why) must be replaced. In addition, the current installation requires a separate meter (cost of around $25 per month just for the meter). Actual electricity usage is minimal, only around $3 per month. Existing plumbing is 2" PVC from the meter to the pump-house (around 40 ft), then a large-ish pressure tank (120 gallon?) with the existing pump, and then around 700 ft of 2" PVC to reach the house.

I want to change this to something less difficult and expensive to maintain and operate. This would probably be a "can" or sealed cistern to replace the pumphouse, which would keep everything below ground, with a submersible pump in the can. This eliminates freeze-protection issues, as well as the monthly meter charge. The small problem with this is that to power the unit from my house will require 400 to 700 ft of wiring (one direction).

The water-system guy recommend a new Jacuzzi VFD system (no specific pump or motor at this point) as a submersible pump in the can.

My specific questions about this setup are as follows:

1. How do I use the pump-curves to choose the most appropriate pump?
2. Am I right that a 3-phase motor is probably better in this situation?
3. Can I find an affordable 3-phase converter without having to spring for a VFD controller that I won't likely use?
4. How do I size the proper cycle-stop valve for this situation? I would locate it at the service entrance (water that is) for the house, not at the pump.
5. Anything else I should be aware of to achieve the best system for my situation?

Many thanks in advance for help with this, and if any of these questions can be easily answered by referring to another thread, please just point me there instead.

 

[Reach4]

I am not a pro. I am trying to understand what you are describing. Your answers may clarify your question for those more knowledgeable about pumps. I do understand pump curves.

I think you are saying that you plan to get 3 or 4 power wires buried to run down to the pump from the house.

It would be simpler to run 240 single phase. The wire size might have to go up a bit but not much vs 3 phase.

My home requires a lift pump for local municipal water to reach the house. Static water level of the municipal supply is about 60 ft below my house.

1a: At 60 ft below the house, the supply is down to zero PSI, and the actual supply point is significantly lower than that
1b: or the pressure is some amount such as 30 PSI at 60 ft altitude?

2. Is this can going to be
2a: at atmospheric pressure with the city water filling this cistern with a float switch or float valve.
2b: some pressure as supplied by the by the city, and the pump in the cistern will act as a booster to add to that pressure

It may be that a multi-stage booster pump protected from freezing would let you get your pressure up top without having to have a cistern at the bottom.

 

[Sponsor]

 

[Smooky]

You need a pressure booster system. This thread may be overkill for what you need. Maybe valveman will chime in with some advice. There is some good info here:

https://terrylove.com/forums/index.php?threads/adding-a-pump-to-city-water.59738/

 

[DaveK01]

I think you are saying that you plan to get 3 or 4 power wires buried to run down to the pump from the house.

Yes. Whether I bury 3 or 4 wires doesn't matter much to me. It will be in 1" (or perhaps 1 1/4") conduit, so expensive 4-wire direct-bury cable wouldn't be needed.
​

It would be simpler to run 240 single phase.

Indeed it would. However, 3-phase motors usually have much better starting characteristics, and are far more tolerant of voltage drops on long power supply runs. On one pump/motor I looked at, I could easily use 10 ga wire with the 3-phase moter vs having to choose between 6 and 8 ga with the equivalent 2-phase motor.​

1a: At 60 ft below the house, the supply is down to zero PSI, and the actual supply point is significantly lower than that.

That's it! The existing pump is about 50 ft (elevation) down the hill from where the static water level would be.
​

2b: some pressure as supplied by the by the city, and the pump in the cistern will act as a booster to add to that pressure.

Yes, that is what I need to do. There's quite enough supply to keep a sealed "can" full to feed the pump. A float valve on something like this would just add unneeded complexity. At worst, I'd put in some kind of pressure switch to shut it down if supply pressure dropped near zero.
​

You need a pressure booster system. This thread may be overkill for what you need. Maybe valveman will will chime in with some advice. There is some good info here:

https://terrylove.com/forums/index.php?threads/adding-a-pump-to-city-water.59738/

 

[DaveK01]

You need a pressure booster system. This thread may be overkill for what you need. Maybe valveman will will chime in with some advice. There is some good info here:

https://terrylove.com/forums/index.php?threads/adding-a-pump-to-city-water.59738/

Thanks for that info. Unfortunately, that's pretty close to what already exists. I'm trying to accomplish several things at once here, and the existing system just won't do. In addition, the existing pump is on it's last legs, so replacement is mandatory. Anyway, what I need to do is the following:

1. Get rid of the $25 per month meter that lets me buy between $0.50 and $2.50 of electricity each month to run the pump. When you run the numbers on that, it's worth spending several thousand $ to avoid a separate meter. (It's $25 per month, forever, until they raise the meter fee yet again).

2. Get rid of the above-ground pump-house and equipment that is too far from the house, and too exposed to vermin like copper-coyotes. The existing pumphouse will cost around $4,000 to replace (8' x 12', with roofing, insulation, heat tracing for equipment, rewiring electrical, and other construction costs. It's a long story as to why the pump-house is so big, but it was the choice of a previous owner.

3. Get rid of any need for heat-tracing the pumping equipment to prevent freezing.​

My plan for the new system is to have the pump controller located near the water entrance for the house, and to include a CSV at the entrance as well. As near as I can tell, the CSV needs to be sized to allow around 3 GPM of minimum flow.

 

[Reach4]

1a: At 60 ft below the house, the supply is down to zero PSI, and the actual supply point is significantly lower than that.

That's it! The existing pump is about 50 ft (elevation) down the hill from where the static water level would be.

Looks to me as if 1.5 HP pump is enough. Figure about 230 ft of head that you need to add, right? 140 ft of head gets you 60 PSI for the house. Then 50 more feet of elevation. Maybe another 20 ft (uncalculated guess) for dynamic losses.

So why was the old pump 3 HP? I don't know.

The pump would be below the the 50 ft elevation point to make sure you could get enough flow to your vessel.

A 3-phase converter is something to buy and something that can fail.
Green lines are about 230 ft of head. Actually, you don't need your max flow rate at 60.... If you were running 40/60 PSI getting your 40 PSI at about 46 ft less head than for 60 PSI (about 184 ft of head). The 200 ft line would be an easy compromise in looking for your 20 GPM.

 

[Craigpump]

How come the water company won't put water to your home? If you're paying for the water, they should get it to you. If the pressure is insufficient, then you can add a booster.

 

[Valveman]

I don't think Jacuzzi even makes a pump anymore since they sold out to Franklin. You would need a 3HP in a single stage centrifugal to get the 200' of head needed. But if you go with a multi-stage pump you can get the same water and pressure with a 1HP. The submersible in a can is one way to do that, or you can just get a multi-stage booster like a Sta-Rite HP20E, as it would be much easier to install and maintain.

You would need to work with a 80/100 pressure switch, a CSV1A setting of 90 PSI, and at least a 20 gallon size tank. This would deliver as much as 17 GPM to the house at about 60 PSI. The 1HP would only need #8 wire to go 700'. This would all probably fit in about a 4X4 well house.

The #8 wire needed for single phase is not that much bigger than you would need for 3 phase, which would require a phase converter or a VFD, and would add considerable cost and complexity to the system.