Advice on pump size for new irrigation well for Greenhouse business

[Theplayer11]

I just had well dug 400'. I will use the well to water my greenhouse, no pressure tank. The well digger estimated around 12-15 GPM for the well, but did not test yet. He wants to order and install a Berkeley pump 200' down, The static level is 48'(I measured with fishing pole) First of all, Isn't the exact GMP needed to properly size the pump?
My watering needs:
1) fill a 1,500 gallon holding tank that is 100 feet away from well, 10' high, same ground level as the well. I will use a a standard 5/8 garden hose to fill. I then use a booster pump to water my greenhouses that are 200' long. I currently get about 8-10GPM from the end of hose with a standard 400 water breaker at hose end. The pressure is fine
2) If possible, water the greenhouses directly from the new well with standard 5/8 hose. The nearest greenhouse would use 200' of hose, the furthest 350'. I would like to get the same 8-10 GPM.

He is suggesting a 15GPM 1.5HP Berkely pump. I checked the pump curve and it's off the chart until 80ft, which would be 20GPM at zero PSI. How would I figure PSI I'm using to read the pump curve correctly? 200' would be 16.3GPM at zero psi, 14.4 at 20 PSI. My initial thought was that a 1.5 hp pump seems too high. My current well at 160' is using a 10GPM 1/2 HP Goulds pump.
Obviously, I don't want to over-pump the well. I could always tweak it down while filling the holding tank. Shouldn't he test the recovery rate of the water before ordering a pump?
Using the pump curves, it states "pumping depth in feet". That would be the water level, not the actual pump depth..correct?

Thoughts?

 

[Valveman]

You could use a smaller pump if you were just filling the cistern. No matter the pump setting, it is only lifting from the water level, so 50' or so to start. But I would expect the well to pull down when pumping it hard. You need to add at least 138' to the pumping depth when using it with a pressure tank or supplying sprinklers directly from the well. The drawing below shows a system where you can draw directly from the well or from the storage tank and booster pump.

 

[Sponsor]

 

[Theplayer11]

You could use a smaller pump if you were just filling the cistern. No matter the pump setting, it is only lifting from the water level, so 50' or so to start. But I would expect the well to pull down when pumping it hard. You need to add at least 138' to the pumping depth when using it with a pressure tank or supplying sprinklers directly from the well. The drawing below shows a system where you can draw directly from the well or from the storage tank and booster pump.

View attachment 65208

thanks for the prompt reply. What do you mean by add 138' to pumping depth? I should also add that the pump will be running 5-6 hours straight on many days during summer months. No sprinklers, just hand watering with garden hose with water breaker nozzle.
edit..also, what PSI should I be looking at on the pump curve charts for watering from garden hose, no pressure tank? thanks

 

[Ballvalve]

If you just want to get water at the end of a 350 foot hose, do what you have now again, a 1/2 hp 18 or 20+ gpm. Certainly you do not need 1.5 HP! More is not better here as the pump will cycle endlessly. Why not just install a small 20 gallon diapohragm tank and set the cut out pressure high, like 70 or so. I have 2] 3 bedroom rentals on a 1/2 hp Teel pump for 20 years with a 56 gallon pressure tank. Never lost water yet. Just dont buy a Chinesium pump on Ebay or Amazonia.

 

[Theplayer11]

If you just want to get water at the end of a 350 foot hose, do what you have now again, a 1/2 hp 18 or 20+ gpm. Certainly you do not need 1.5 HP! More is not better here as the pump will cycle endlessly. Why not just install a small 20 gallon diapohragm tank and set the cut out pressure high, like 70 or so. I have 2] 3 bedroom rentals on a 1/2 hp Teel pump for 20 years with a 56 gallon pressure tank. Never lost water yet. Just dont buy a Chinesium pump on Ebay or Amazonia.

the pump will not cycle as there will be no pressure tank and switch. I will just turn and on and water greenhouses 3-6 hours straight. I think the key is knowing exactly what the well is producing. It would be nice to be able to run 2 hoses at the same time as well, or being able to water greenhouses on 1 hose and have another hose filling the holding tank.

 

[Valveman]

Even without a pressure tank you will need a pump that can do at least 40 PSI. Hose irrigation doesn't work very well unless you have some pressure pushing water out of the hose. Takes some pressure just to squirt a ways with your thumb over the hose or when using a spray wand of some kind.

 

[Theplayer11]

Even without a pressure tank you will need a pump that can do at least 40 PSI. Hose irrigation doesn't work very well unless you have some pressure pushing water out of the hose. Takes some pressure just to squirt a ways with your thumb over the hose or when using a spray wand of some kind.

Maybe that's why he's recommending a 1.5hp motor. A bigger motor produces more PSI, or unrelated?

 

[Valveman]

Yeah that 1.5HP, 15 GPM pump would build some pressure. Almost three times as much as the 1/2HP, 10 GPM pump. But either one won't be able to build any pressure if you open up the hose all the way and use more water than the pump can produce.

 

[Theplayer11]

Yeah that 1.5HP, 15 GPM pump would build some pressure. Almost three times as much as the 1/2HP, 10 GPM pump. But either one won't be able to build any pressure if you open up the hose all the way and use more water than the pump can produce.

they just tested the pump at 200' and I was getting about 8GMP from each hose end running 2 hoses. The PSI was about 40. Running 1 hose the PSI was around 80. At 80 feet the recovery rate was 13GPM. He could only run about 1/2 hour before the generator quit, amps were too high.
I'm very satisfied with the results so far. Little nervous about 80 PSI running 1 hose, may have to run another line at same time and tweak it down a bit. He said there is a relief valve at 100PSI.

 

[Valveman]

You don't have to use a pressure tank/pressure switch to make a Cycle Stop Valve keep the pressure at a steady 40 or so no matter how many or how few hoses you are running. Attach a 40 PSI CSV125-1 to the pump and you will have a constant 40 PSI when running anything over 1 GPM.