Use of Well Pump for Irrigation

[OBX Guy]

I have installed several irrigation system but they have all been on city water with good pressure.
Now I am in Brazil building a house for the in-laws....
I have a swallow well with 4.5m depth. I am using a 1" pipe to the pump. The pump exit is 1" going to a 3000 liter tank about 8m high. I don't really care about how long it takes to fill, anything around 500 to a 1000 liters is fine. However I want to use the pump for irrigation also.
I am choosing a Schneider self priming centrifugal 3 phase pump rated at .75CV (MBA-ZL) I am an electrical engineer so I like 3 phase stuff. This gives me 10 GPM volume which is enough to feed 5 to 10 1806 rainbird heads. Don't have any large areas. This gives me about 10 zones. I could go to a 1CV pump and use less zones but I'd rather fill the water tank at a slower rate.
So the question..... will this work since I do not have a tank for the irrigation system... just pump direct to sprinkler heads. I do not want to use the 3000 liter tank because it is feed from the well and city water. The city water has no pressure to use for irrigation and better to use free water than chlorinated water.
Any input would be appreciated.... Just didn't want to buy this pump and then find out a different pump would have worked better for dual purposes...

 

[Reach4]

Well diameter is not big enough for a submersible? Those are centrifugal too. Those need no priming, which is better than self priming. About twice the pumping per watt.

Some above-ground pumps are jet pumps that increase pressure by using a nozzle and a venturi. Irrigation pumps usually do not have a jet, and may have more than one centrifugal stage.

Does 0.75CV mean 0.75kW? HP?

 

[Sponsor]

 

[LLigetfa]

I have a swallow well with 4.5m depth.

I think you meant shallow. 4.5m is less than 15 feet for our American friends.

What is the static level? What is the recovery rate? Do you know what the cone of depression is at the GPM you plan to draw?

 

[WorthFlorida]

One pump to fill a 3000 liter tank and then want to use the same pump for irrigation? Is the pump an above ground jet or a irrigation pump? How are you going set up to be able to switch between filling the tank and irrigation? For irrigation are you purging the storage tank or the well itself? Is there a pressure tank and is the water in the tank be used for domestic water for the new home? Any idea what the hydro static water level is and its test flow rate?

What you need to plan is prevent cross contamination between the domestic water supply and irrigation system. A backflow preventer is needed. Without much more information it is difficult to give an definitive answer. In my book keep it simple, use two pumps. One to fill the tank, the other for irrigation. In the USA irrigation pumps are 1.0, 1.5, or 2.0 HP for residential use. There is 3.0hp centrifugal pumps for irrigation but usually used for very large irrigation systems.

 

[OBX Guy]

Thanks for all the comments.... I will try to answer what I know....
I do have a 4" casing so a submersible can be an option.
The thought is to fill the tanks with either city or well. The choice being by ball valve. Really didn't think that mixing the two would be a problem.
There is a back-flow on the pump side so the water would never return to the irrigation, good idea for back-flow on irrigation.
Th switch from tank to irrigation would also be by valve... maybe automation at a later date.
.75CV is pretty close to 3/4HP
I was told that well is capable of between 5000 to 6000 LPH 3/4HP would provide 2400LPH
Not sure of the static pressure, actually what you are looking for... I may know with further definition
No idea what the cone of depression is...
I had not planned on using a pressure tank... very limited on space...
Again I thought the well is free and would be good for irrigation... dual use of the pump...

 

[LLigetfa]

Not sure of the static pressure, actually what you are looking for... I may know with further definition

Static level
The natural level the water is at after the well has fully recovered.

Cone of depression
https://en.wikipedia.org/wiki/Cone_of_depression

 

[WorthFlorida]

The water level acts on the pump capacity. If you look at the specs, the depth of water varies the output flow.
With your shallow well, only about 25 feet deep, the water level may be higher, an irrigation pump would work. Use a float switch for the tank for operation. For irrigation, add some valves and a bypass switch off the float.

 

[Valveman]

If you want water when you open a faucet you will need a pressure switch and pressure tank. If you are limited on space you can do this with a 4.5 gallon size tank using a PK1A kit from Cycle Stop Valves. There are lots of other benefits to the CSV besides the smaller tank if you want to look them up. An irrigation or sprinkler pump does not usually build enough pressure to work with a pressure switch, so they need an automatic timer to start and stop them according to the irrigations needs. An irrigation timer with a pump start relay will not give you water when you just open a faucet.