Irrigation well pump and CSV question

[asfd]

Hi everybody, I am sorry for the long post but I am a bit confused right now.

I just had a 6" well drilled mainly for irrigation purpose. It is 200' deep and static water level was estimated at 20', dynamic (pumping?) level at 60' and recovery rate at 100 gpm (no real recovery test was done).

The well is drilled about 180' from a greenhouse to be irrigated and a field, located about 400' from the greenhouse, is to be irrigated too.

The water requirements are the following: about 25-30 gpm @ 20 psi for drip irrigation, 18 gpm @ ~40 psi for sprinklers and 10 gpm @ 60 psi for manual watering in the greenhouse.

The salesperson at my plumbing supply house was advising me to go the Grundfos SQE route but it seems most of you guys don't like that system. So I am considering going the CSV way (I am particularly attracted by the 3000 rpm of a standard pump vs the 10000 rpm of the SQE). I am thinking of installing the submersible pump at about 80' down, connected with polypipe to an in-well CSV, to a pitless adapter (5' deep), to the greenhouse via polypipe. In the greenhouse I would have a small heated pump room housing a ~20 gallon pressure tank and the pressure switch. Does this seems acceptable?

I am also wondering how I should choose the pump/CSV setting to go with my needs. What kind of pressure drop should I expect from the different parts in the system (the pipe from greenhouse to field would be 2"-3" diameter)? How does the CSV work when the demand is such that pump's available head is lower than the CSV cutoff? Is the CSV wide open then?

For example, I am thinking of using a pump like Franklin Series V 25 gpm with a CSV set at 60 psi. When demand is low, if only part of the drip irrigation is working at 6 gpm for example, the CSV prevents the pump from cycling by keeping it at 60 psi. When Full flow is needed, the pump is able to provide 27 gpm at 30 psi from a 60' pumping depth. What happens then?

I know I need pump wire with insulated ground in the well but I would like to know if it is acceptable to use straight UF wire up to the well and switch to pump wire in a junction box.

Finally, I would like to know what are the options to be able to use 1.5"-2" poly pipe between well and greenhouse. Is it acceptable to use an adapter buried on the outside side of the pitless adapter to step up from 1.25" to 2" pipe.

Thank you all for your time!

 

[Valveman]

A 1 HP, 25 GPM pump can’t produce 30 GPM at 20 PSI if the pumping level is 60’. A 1.5 HP, 25 GPM pump will produce too much pressure and flow, especially if the pumping level doesn’t drop to 60’. It is hard to size a pump to exactly match all those different needs. But the CSV designed to let you put in as large a pump as you may need, and still be able to run it like a small pump anytime you want.

Use a 25 GPM , 1.5 HP, with a CSV1-60 in the well, and a CSC1 to hold the weight. Use a 20 gallon tank with a 50/70 pressure switch.

That will give you a constant 60 PSI for anything up to 20 GPM, as long as the pumping level stays up at 20’. When you use more than 20 GPM, or the pumping level drops in the well, the pressure will drop below 60 PSI, and the CSV basically turns into a piece of pipe. The CSV will just open up and let you have whatever the pump can produce. That pump will produce about 33 GPM at 20 PSI, when pumping from 20’. If the pumping level drops to 60’, it will still produce 31 GPM at 20 PSI.

That pump will also produce 40 PSI for the sprinklers. But at that pressure, it will want to produce 30 GPM from 20’ and 27 GPM if the pumping level drops to 60’. So you just set the system up to run three different pressures.

Running straight off the CSV and pressure tank, you will have 60 PSI constant, and 15 to 20 GPM, depending on the pumping level. Then use a 40 PSI pressure reducing valve on the line going to the sprinklers, and a 20 PSI regulator on the drip zone. This way you can run as many or as few sprinklers as you want at a steady 40 PSI. You can also run as many or as few drip zones (down to 1 GPM) at a steady 20 PSI. And you still have a constant 60 PSI straight from the CSV where needed. You can even run all these different things at different pressures all at the same time, as long a you don’t use more water than the pump can supply.

You can run whatever kind of wire you want to the well head. As long as it is the right size, has the right number of insulated conductors, and will pass any codes for your area. And it is very common to step up the pipe size right out of the pitless, to use as large of pipe as needed for the flow and distance.

 

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[asfd]

So if I get it I just have to size the pump for my pumping level and maximum flow @ 60 psi. Set a 60 psi CSV and it will prevent the pump for cycling even when used flow is below the capacity of the pump down to a demand of 1-2 gpm.

My pressure tank would be used for small draws and long periods of low flow (for example small drip irrigation zone). How can I know how long would the pump stay on to refill a ~20 gallon pressure tank?

Thank you!

 

[Valveman]

So if I get it I just have to size the pump for my pumping level and maximum flow @ 60 psi. Set a 60 psi CSV and it will prevent the pump for cycling even when used flow is below the capacity of the pump down to a demand of 1-2 gpm.

My pressure tank would be used for small draws and long periods of low flow (for example small drip irrigation zone). How can I know how long would the pump stay on to refill a ~20 gallon pressure tank?

Thank you!

That is correct. The CSV will hold at 60 PSI and not let the pump build to 70 PSI and shut off, as long as you are using more than 1 GPM. And you can use pressure regulators on lines after the tank to supply 40 PSI to one line and 20 PSI to another, while the CSV is operating at 60 PSI feeding everything.

The tank is for small draws (washing hands or toothbrush), but you don’t really want to use it for long periods of low flow. Just don’t run anything less than 1 GPM. A 20 gallon tank holds about 5 gallons of water at 50/70. So it should take the CSV about 2 ½ minutes to fill the tank from 60 to 70 after you finally turn off all the faucets.

 

[asfd]

Thanks again valveman for your quick reply.

A few final consideration:

the CSV1 is rated 1-25 gpm. If I am drawing 30 gpm is the only problem I will get is a large friction pressure drop (8 psi according to the graph)?

Does anybody knows of any Canadian (preferably in Quebec) distributors of the CSV?

 

[Valveman]

8 PSI is the only drawback to 30 GPM through the 1" valve. It will work fine. Call me and I will get you some numbers in Canada. 800-652-0207