mailbag: Irrigation Pump

Larry Bachus
(a.k.a. “Pump Guy”)

From: Glen P.
To: Larry Bachus
Subject: Irrigation Pump

Hi Larry,

I work at a Tennessee paper mill and always read the “Pump Guy” in Flow Control. I’d like your input regarding an irrigation pump application at my farm.

I want to divert some creek water to fill a catch basin/spa. Then I want to use this water to irrigate my garden.

I want to put a pipe in a creek about 200 yards from my garden and pump water to a large in-ground catch basin. The in-ground catch basin will also serve as a natural cool water pool/spa to enjoy with my wife and family on hot summer days.

The level of the water in the creek is slightly above the top rim of the catch basin. The catch basin is below my garden. One pump will lift the water over the levee. From there, the water will flow downhill into the basin.

I am thinking of using the power-take-off (PTO) on my tractor to power the pump. Do you have any suggestions for a pump that will hook up to a tractor PTO and do the job? Is it best to locate the pump at the creek and push the water to the basin? Or, is it best to put the pump close to the basin and suck the water from the creek? What diameter pipe should I buy for this project?

I’m going to open a ditch with a slight drop toward the basin and lay 200 yards of pipe in the ditch from the creek to the catch basin near my garden. I will make the in-ground catch basin out of concrete with the water flowing in at the top and an overflow pipe at about the same level.

Because of the topography I would need another pump to lift the water from the basin and slightly uphill into my garden. Gravity only works to move the water source about 200 yards closer to my garden. I’d still need to pump it through a hose about 150 feet long. I was thinking of using a standard irrigation or cold-water pump with a 110-v pump. What do you think?

Glen P.

From: Larry Bachus
To: Glen P.
Subject: RE Irrigation Pump

Hello Glen,

The project is doable. If you build it now, it will be ready as the planting season and warmer weather roll around.

You really have two systems. One system is the creek to the catch basin/spa. The other system is the catch basin to the garden. Let’s consider one system at a time, starting at the creek.

According to your description, the creek water will flow naturally downhill about 200 yards from the creek toward the catch basin/pool. You only need a pump to lift the creek water over the levee. Mother Nature will do the rest.

Go to a farm or tractor supply store; they will have pumps that work with tractor PTOs. If you can’t find an adequate pump, you might consider a submersible pump located in the river. It only needs to lift the water over the levee.

The pipe diameter from the creek to the basin is not so important as long as it keeps your catch basin/pool mostly full. Without knowing more, I’d use larger pipe with a valve located at the catch basin. Your pump will fill the pipe. You may only need the pump to establish prime once the siphon effect takes over.

Locate your pump close to the creek, on the levee if possible. This is probably the highest point in the pipe. One end of the pipe is submerged into the creek. The other end slopes downhill toward the catch basin. When the pipe is filled with water, and siphoning, the pump and upper portion of the pipe will be in a vacuum. So, you might consider plastic welded PVC pipe, or a hose to prevent losing prime thru a gasket. Locate a valve at the basin to regulate flow into the basin.

The next system is from the catch basin/pool up to your garden. You will need another pump to elevate the water. Let’s say it is 15-ft from the level of the water in the basin up to the ground level at the garden. Then you will want a pump that generates at least 15 feet of head. Also, the pump must overcome the resistance thru the pipe. Now, larger pipe diameter is important because you pay the power bill. Let’s say the velocity and friction losses are 2-ft. of energy. Your pipe shop can help with resistance losses. The total would be 17 feet (15-ft elevation + 2-ft. resistance). You will want a pump designed for 17 feet of head.

Next, decide how much flow you want into the garden. I don’t know the size of your garden, but let’s say you have 300 corn stalks and 200 tomato plants. Let’s say that each plant and stalk needs about three gallons of water each day. Then you need 1,500 gallons per day of flow into your garden. (500 plants x 3 gallons per day)

Next, do you want the flow as a slow drip over 24 hours? This computes to about one gallon per minute with the pump running 24 hours per day. You can get a pump for this type service at an aquarium supply store and run it on 110-v electricity. You want a pump that generates 17 feet of head @ one GPM. (It may be a positive-displacement pump.) At 1-gpm, it wouldn’t tax your catch basin/pool.

Or, is it best to water the garden once per day? If you pump 50 GPM, you can water the garden in 30 minutes per day. If you pump 100 GPM, you can water the garden in 15 minutes each day. The pump runs only 15-minutes per day.

We never discussed the size of your catch basin/spa. Can you drain it at 100 GPM for 15 minutes without draining it? And will the level recover for the next day’s irrigation?

At 150 GPM, you can water your garden in 10 minutes each day. You can buy a pump for this service at a pool supply store and run it on 110-v electricity. Tell the sales clerk you want a pump designed for 17-ft. of head @ 150 GPM.

Good luck with your project.

Regards,

Larry Bachus

Larry Bachus, founder of pump services firm Bachus Company Inc., is a regular contributor to Flow Control magazine. He is a pump consultant, lecturer, and inventor based in Nashville, Tenn. Mr. Bachus is a member of ASME and lectures in both English and Spanish. He can be reached at [email protected] or 615 361-7295.

www.bachusinc.com

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