Interesting irrigation idea water from pond

[Michael A DeMarco]

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Looking to pump pond water into my irrigation system around 60-75 gpm and 45 psi needed, watering acreage so expecting runs that are 300-500 feet long worst case.

Was researching an inline trash pump, to pull water from pond and handle the pressure side operation, but had an old landscaper give a very interesting idea.

His point is we (two buddies building similar systems) will always be fighting debris and contamination on the intake side on an inline pump. He proposed that we dig a trench the depth of the pond and 2-3 feet wide perpendicular to (away from) the pond. At the end away from the pond sink a 4-6 inch perforated casing for a well pump and back fill the trench with 1"minus rock and let the pond flow into the trench filled with rock towards the well pump. The rock will filter the water and catch debris by the time it gets back to the pump.

He has done this several times with good results. I have high groundwater and would likely wrap everything in fabric, or have considered getting fancy and building an r-tank system with fabric barrier and pull water from that.

The benefits are the filtration, no inlet into the pond, and possibly some advantages to the well pump vs inline pump.

Any thoughts?

 

[Reach4]

The benefits are the filtration, no inlet into the pond, and possibly some advantages to the well pump vs inline pump.

Submersible pumps are much more efficient than suction pumps. I suspect you would use a 6-inch pump with more than one stage. A trash pump, as I understand it, would not usually develop high pressure. But a 2 or more stage irrigation pump can.

I was originally thinking of 4 inch pumps. Those are not for the flows you need as far as I can tell.

 

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[Valveman]

Wet Wells as they are called, are very common. We work with a lot of them for golf courses. The Screen or the rock is still going to get clogged over time. They make spinning and self cleaning intake screens that use a little of the pumps water to continually flush the screen. Here is one with a bottom intake. You can also make a top intake so that you can install a large pump in a deep pit, even if the pond is shallow.

To get 75 GPM at 45 PSI you will need a 3HP like the Grundfos 75S30-5. If you want to make it completely automatic with variable flow and constant 45 PSI pressure, the CSV3A2T with a 44 gallon size tank and a 35/55 pressure switch would work great.

 

[Michael A DeMarco]

Cary was hoping you would chime in, I went down Grundfos variable speed control blackhole and ended back at your website. Saw the larger valves and assumed you could supply the tank. That is great to hear.

I am targeting the Grundfos 75S30-5, just need to find it in single phase.

It should be able to handle my needs: the sprinkler heads with rotary nozzles self regulate to the 45 psi they run best at and they flow 3.87 gpm. I would like to be able to run 15 of them at a time, on runs maxing out at 500 feet. My head is the depth of my pond, 10-12 feet. Being conservative, the ponds has 25,000 gallons in it, and the spring which feeds it flows 50 gpm.

On to the wet well, thanks for the term I will go research. The idea we were told was to open the end of the gravel filled trench into the pond, I agree with your image that a socked pipe should be used to essentially fill a fabric lined holed full of gravel with the sump in it. My water is currently pretty clean, maintenance would all come down to how much contamination went in. I also could pump the pond down, and back flush the "sump" to try and clean it out periodically?

Am I on the right track?

 

[Valveman]

If you fill the wet well from the top, like with a ditch to the pond, floating stuff will be the problem. If you have the pipe to the pond too deep, muck from the bottom will be a problem. A floating suction, held slightly below the water surface is the cleanest place to get water.

You could also use a Goulds 75GS30 and either should be available with a single phase motor. You will probably need to purchase the pump, motor, and control box separately. I would get a deluxe control box, which takes all the load off the pressure switch. These are 4" pumps. At 50-75 GPM they will require a 5" flow inducer or shroud, which is important in a wet well.

Everyone will try to get you to use a three phase motor and a VFD. But since you have previously been down the VFD blackhole you already know the Cycle Stop Valve is a better way to get constant pressure, use a small pressure tank, and get the soft start/stop that helps save check valves and lots of other things.

 

[Michael A DeMarco]

OK, about to order a Grundfos 77s30-6 77 GPM 4" pump with a 3hp Franklin motor

Have secured 4' diameter manhole sections and will construct a 8' tall vault with sealed connections, a filtered inlet from the pond, with a sluice gate to control flow. Will wrap in fabric, bed in gravel, have a sewer manhole lid for access, can pump it dry in the winter.

I am going to run through a cycle stop valve and need to maintain 40-60 psi at 60-70 gpm through 2" hdpe runs to valve boxes down to 1" hdpe for individual zones. These runs may be 500-700' at their absolute longest. Most will be 100-300'

Any input as I start spending money?

Thanks!

 

[Michael A DeMarco]

Can anyone help me size the pipe from the pond into the "vault" I am about to install?

I can pump 75 GPM from the vault, need to make sure the piping from the pond to the vault can handle that flow. I am sure there will be a bit of "suction" created, but I do not want to undersize. I also do not want to oversize, I would like to bury an inline gate valve which spirals out of control as the pipe size goes up, so 4" would be great.

The vault will be 20' or less from the pond, and 2-3 feet underwater so around 2 psi of head behind it.

Any advice for me?

 

[Reach4]

I would think 3 inch pressure-rated solid pvc would be best, but 2 inch would be big enough it seems.

http://irrigation.wsu.edu/Content/Calculators/General/Pipeline-Pressure-Loss.php