Solar Irrigation Question

pabloesguapo · December 2011

We just punched a well on our new property. It is 205 ft deep, and can provide 70 gpm! Our HOA's CC&R's limit us to 15gpm. I am thinking of running a Grundfos 11SQF-2, providing 11-12gpm into a very large storage tank.

I have received a lot of assistance in configuring the household water supply, so I have that pretty much sussed out. But I would also like to use this well to irrigate a few acres of my land in addition to providing H2O to my house. The well is at the same level for about half this land I want to irrigate, and even a bit below some of it too. How do I provide enough pressure to irrigate a few acres worth of land, especially the land that is uphill?

BB. · December 2011

Re: Solar Irrigation Question

Pressure*Volume cost you money...

Are you going to flood/channel irrigate or are you going to use nozzles (40-60+ PSI? or about another 60-100+ feet of head)?

If you can pump to a cistern/lined pond, then you can pump as need with appropriate pump(s) (flooded or pressure) to the various points on your property.

-Bill

pabloesguapo · December 2011

Re: Solar Irrigation Question

I'd like to use drip irrigation. That's 15-30 psi, I think?

So, how to pump water uphill and pressurize it?

I was originally planning on pumping directly from the well into a large cistern/tank, something like this. That was to hopefully gravity feed into my house, where I would have a pressure tank LIKE THIS.

I'm thinking of several different ways to add on irrigation:

1) Pump out of this main, large tank uphill to a secondary tank for irrigation. Do I use an additional electric pump to do this? Once I get the water to the second tank, (do I bother with a tank at all if I have a strong enough pump?) how do I attain 15-30 psi? That would be an incredibly high water tower. Can I use another pressure tank? The biggest one I can find is only 120 gal. This seems impractical.

2) Move this primary tank uphill, away from the well itself a few hundred feet horizontally, but only an extra 30-40-ish feet vertically, and use this one tank to irrigate my several acre garden/farm AND gravity feed the pressure tank back down into my house.

This is new territory for me. I apologize if these questions seem stupid.

solar_dave · December 2011

Re: Solar Irrigation Question

I think drip is only about 5 psi, I bet gravity feed would be enough if the tank was at the highest point. I could go check my drip regulator here I guess but I am pretty sure it is minimal pressure.

BB. · December 2011

Re: Solar Irrigation Question

Now it becomes a "simple" problem of picking pumps, tank locations, and designing a system (probably several paper designs).

More or less, pumping to a tank at the well head and then again pumping another 50 feet to a second tank--All depends on the pump in/at the well... If it only has enough pressure to pump to the well tank--then you would need a second lift pump.

If the well pump can pump the extra vertical and horizontal distances--then why not install one tank at the top of the hill and use it to pressurize your entire water system.

There are lots of issues (pipe friction, pipe diameter vs flow rate--too large of pipe vs flow could cause sediment buildup in the pipe). Much of this comes down to having an accurate layout of your plumping/well and where you need the water (volume and pressure). Then picking several types of pumps and seeing which gives you the best bank for your buck.

You will find "solar" pumps are very expensive but are very "nice" to your battery/off grid system (little to no surge current, generally very efficient). But, they also tend to be smaller horse power (1,000 watts/fractional horse power) because solar is so expensive.

You can build out a larger solar/battery system to run 1-2 HP in well AC pumps (several people here do it--I believe). But these are not small solar powered systems (can be upwards of a 6kW inverter and >600 AH @ 48 volt battery bank).

In general, with solar power, you are going to be looking for small pumps that run for hours as opposed to a large pump that runs for 20 minutes a day.

But, if you combine your pumping needs with that to run your home--Sometimes the large pumps running for 20 minutes a day are not even the majority of the rest of the home's daily load.

As we use rules of thumb here, when I have tried to help others here--I just searched the web for plumbing/irrigation rules of thumb to get the estimates/sizings for my initial hardware search (I.e., if I need a 2 hp pump for my needs, I am not going to look up a 50 watt solar powered pump). Then go on from there.

-Bill

pabloesguapo · December 2011

Re: Solar Irrigation Question

Hmmm... So, theoretically, I COULD use the Grundfos 11SQF-2. It provides 11 gpm at a max head of 300ft. My well is 205' deep. Assuming we dip it about 30 ft below the water table, that may allow me a few extra feet of vertical to get the water to a tank farther uphill. Or do I have to also account for horizontal distance? If so, I can go with the Grundfos 6SQF-3, which has a max of 820 ft, but I would have to scale down to 6gpm.

And, of course, that doesn't take into account the extra power (PV panels and/or batts) I may need to do this...

tmarch · December 2011

Re: Solar Irrigation Question

What is the water level in the well? That will determine the dynamic head to whatever you pump into. Odds are if the well is 205' the water level is higher than that and you wouldn't want the pump on the bottom of the well.
It's better to use a oversize pump than to pump at the limit of the pump, pumps last longer.
It's cheaper to buy more storage than to upsize your pump in most cases.

mike95490 · January 2012

Re: Solar Irrigation Question

My system (domestic and irrigation) pumps uphill to several (4) 3,000 gallon tanks, which are kept full. They are about 160' feet higher than my pond, and 180' above my home site.
I ran a 3" PVC pipe which is both the uphill and downhill run, my pump connects to a T in the middle. The 3" line also serves as my fire hydrant supply. I have a #180 disc filter after the pump, but before the T that connects the 3" main. The tanks are dark plastic, and mostly in the shade, so they get little algae growth in them. Tanks are fed from the bottom, and cross-tie into my domestic water (3,000 gal also) tank, at the 75% mark, and a float switch and timer control the motor. Everything is gravity feed, if the pond dries up, I can get a tank truck up the road to fill the tanks.

Since it's pond water, I use a slow sand filter and ozonater to purify it.

Solar Irrigation Question

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