Irrigation

MikeL_2

Looking for opinions, experiences, or a guide for best standard practice.

Is it safe to use a submersible pump in a pond or lake for irrigation?

Larry Weingarten

Hi, This is more a question, but keeping the pump free of debris like leaves, twigs and mud seems important. Have you a plan for doing that along with making the pump easy to service? 🤔

Yours, Larry

MikeL_2

Larry,

I'm more concerned about the potential for electrocution. I've always used a jet pump with the foot valve in a pail full of holes.

Jamie Hall

Plenty of submersible pumps used for irrigation — from ponds or rivers or what have you. One thing to remember, though — they are happier when they are in a shroud — length of pipe — which forces circulation past the motor. Not really necessary, but it doesn't hurt. Those motors are meant to be water cooled…

The shroud can be any pipe which is correct for the pum — so a 6 inch pipe, say, for a 4 inch submersible. Seal the "top" end, and put a generous screen on the "bottom" end.

You won't have a problem with crud build up if the pump has no check valve and there is a generous length of pipe beyond it, so that the water in that pipe can flow back and flush stuff off the screen. If the pump is running continuously for days at a time, though, you may want to have a way to shut it off and lift it out now and then!

One thing: submersibles have fairly tight tolerances, and don't get on well with sandy water. For that, use a jet pump with some piping arrangement so that the motive flow doesn't entrain sand. Can be a bit tricky…

Electrocution? Not a hazard if you wire it up exactly as you would any other submersible… No splices underwater! Except at the pump itself, as the manufacturer intends.

hot_rod

I suspended my pond submersible in a cage of 6X6 concrete mesh. Just a rolled up round cage. This kept it off the bottom and it had good circulation all around.

Attach a nylon rope for easy removal without pulling on the pipe.

EBEBRATT-Ed

Use a circuit protected by a GFCI breaker. I wouldn't use a GFCI receptacle near water and the cord on the pump is probably not long enough to get the receptacle away from the water.

hot_rod

It's probably a 240V pump?

MikeL_2

Again, I'm concerned about potential. I've seen it realized too many times in my career. And many plumbing / mechanical codes and best standard practices are partly based on potential.

A 240 volt pump in a pond doesn't sit right with me

Jamie Hall

https://forum.heatinghelp.com/discussion/comment/1905133#Comment_1905133

If you wire that pump in accordance with code and the manufacturer's directions, there is virtually NO possibility of current or voltage getting into the water. You would have to have three faults, at a minimum: the ground interrupted, an insulation failure in the pump allowing one of the hot sides contacting the metal parts of the pump, and the circuit breaker or fuse failing to open. Could it happen? Certainly. Is it likely, no.

Let's assume for the sake of discussion we are looking at a 240 volt, single phase submersible. The pump is powered with three wires (in most cases) on the drop cable: two hots and a GROUND wire (not a neutral in most cases)(in a few cases I've seen, there is also a neutral — this is NOT the same as the ground, and they must NOT be connected except at the main premise disconnect). The GROUND wire is required, by code, to be directly connected to an earth ground — depending on the installation, this may be a local GROUND at the installation, or (for most residences) the main system GROUND at the main disconnect. That GROUND wire is solidly connected to the metal parts of the pump. Thus it is not possible to have a potential on the metal parts of the pump which is different from the ground potential.

Now there is an installation gotcha here: if that ground connection is wired instead as a neutral, it is possible — in fact quite normal — for there to be a considerable voltage on that ground wire in reference to a true local ground, even without any circuit faults being present. The "neutral" in a loaded circuit is carrying current, and thus has a voltage difference from end to end. In a heavily loaded circuit, that drop can be substantial. This problem is more often seen in premises with dispersed buildings which are not wired according to code.

OK. So we've done it right and our GROUND is in fact at ground potential — and thus so is the pump.

Now. What needs to happen to get a potential different from ground on the pump? There must be a wiring fault in the pump to allow one of the hot feeds to contact the metal, or there must be damage on the drop wire to disrupt the insulation on one of the hots and allow metal to metal contact. Unlikely, but if the GROUND wire is intact, that won't result in potential on the pump — rather it will show up as a short circuit from the hot wire.

How is that cared for? Well… for that short circuit to cause a potential on the pump, the GROUND wire must be disrupted AND the circuit protector — fuse or circuit breaker — for the shorted wire must fail to open. Myself I prefer fuses — I've never seen one fail to open on overload, provided it is within its voltage rating — but circuit breakers are somewhat less susceptible to tampering. Someone up there suggested the use of a GFCI breaker; provided one can be found with the correct current rating, this does add a bit of additional protection but only if the GROUND wiring is correctly done in the first place! (A GFCI on a circuit with an improper or faulty ground is worse than useless).

Hope this helps.

Addendum: I'm a bit of a bug on grounding, as I've done a fair amount of work in agricultural settings — and farm animals (particularly horses and cows, for some reason) are much more sensitive to improper grounding than humans are. You can kill a horse with a ground fault leakage which is imperceptible to a human…

MikeL_2

Thanks, Jaime. I appreciate the thorough primer. The potential I'm referring to and am afraid of is the likelihood of unintended consequences.

For instance a metal rowboat or canoe severing the wires leading to the pump. Can this result in electrifying the pond?

Jamie Hall

https://forum.heatinghelp.com/discussion/comment/1905189#Comment_1905189

Not if you have proper protection on the circuit. The fuse or circuit breaker will operate essentially immediately. If you have both a fuse and a GFCI on the circuit I would say it would be almost impossible.

EBEBRATT-Ed

240 volt is not an issue. They make 240 volt GFCI circuit breakers. They are required on 240 volt Hot Tubs etc. they are used every day.

The higher voltage means nothing, Both legs of the 240 are 120 to ground the same a 120 volt circuit.

hot_rod

maybe there is a gas powered pump in your future?

MikeL_2

My original post was in response to a submersible pump I saw recently in a pond adjacent to a customers back yard. And right next to a docked canoe & child's play area.

I've seen submersible pumps before, mostly in a large lake I work nearby often; the lake authority banned the use of submersible pumps for irrigation decades ago.

I've always installed jet pumps for irrigation and garden watering. As I said before, bodies of water & exposed wiring doesn't sit well with me - the same way I don't like csst, pvc combustion vent piping, copper header on a steam boiler, stacked bowl waxes, plastic relief valve drop pipes, buried shark bites, etc.

Jamie Hall

How do you feel, then about buried electrical mains in your street (12,800 volts?) Subsea high power interconnects (546,000 volts, usually DC)?

For that matter, my friend, what about the submersible pump in your well?

There's always something out there to be afraid of… anything you don't understand.

MikeL_2

There are circumstances beyond my control that I accept. I choose not to use a submersible pump in a pond and not to tempt fate.

I understand that all the stars have to align for a mishap, but common sense tells me when potential exists it can be realized. And there are plenty of documented cases of electrocution from exposed wiring and submersible pumps.

leonz

The safest and simplest way to pump surface water for irrigation is to use a simple three point hitch mounted PTO powered centrifugal pump powered by a compact tractors 540 RPM power take off.

hot_rod

The installation can be done safely and to code.

If you are not comfortable with it, that is a different discussion, it doesn’t seem like you mind will be changed.

Go with what makes you comfortable.

leonz

Just so you understand this in greater detail a tractor mounted three point hitch mounted irrigation pump will be a 4 inch pump andwill require 4 inch aluminum irrigation pipe, pipe clamps, elbows, spray nozzle heads, various fittings and hose if required for your needs. A simpler method is described below:

As you seem to be new at this and wish to use surface water to irrigate a floating gas engine powered 2 inch fire pump will be your simplest method to do this and provide you with massive amounts of surface water for flood irrigation.

I can help you with this, but you need to provide me with more information.

The folks at www.absolutewaterpumps.com have an extensive line of water pumps that could be used for irrigation using 2 inch hose.

You need to narrow your focus with your inquiry as there are a number of things you need to decide on that have to be set in stone long before you begin using a decision tree or the ben franklin closing argument with the plusses and minuses and come to a conclusion.

Leon

Jamie Hall

OK. We have ruled out a submersible.

Now. You first, need to answer 2 questions: how much flow are you looking to get, and what is the pressure you need to have (in most irrigation applications, that would be the elevation difference between the water surface and the irrigation spray or drip heads or the outlet for flood work, and the required pressure at the spray or drip heads (it's zero at a flood outlet).

Then we can start thinking about what kind of pump.

Except for very low flow applications, jet pumps are horribly inefficient. They have their applications, but irrigation isn't one of them. Wrong tool.

@leonz mentioned floating gasoline powered fire pumps. They do work splendidly, but there is an almost 100% chance of gasoline or oil from the engine getting into the water body. I wouldn't, except for a fire.

Assuming that you need a pretty good flow, and can get power to a location more or less near the water body and not more than about 5 feet above it, my choice would be a self-priming centrifugal irrigation pump. Yes, they are made for just that application. High flow, high efficiency, but usually rather low head. Also not particularly expensive for the capacity. Gasoline or diesel powered models are available, but they do use a lot of fuel…

Jamie Hall

Now I don't want to rain on your parade, but where are you located? In many locations, you must have any one of several varieties of diversion or use permit to pump water for irrigation. In many areas this is overlooked for small diversions (a few hundred gallons per day), but in some the rules are very strict — and the penalties are draconian.

MikeL_2

I apologize if my original query was misleading. The dozen or so irrigation, watering, or drip tube piping & pump installs I've done were mostly small residential gardens, shrubbery beds, and zoned lawn sprinklers. All easily handled by a 1/2 HP jet pump & 30 gallon tank. Never any severe elevation challenges.

I posted because of how infrequently I've seen a submersible pump used for lawn & garden watering, and my genuine concern for safety. I'm also interested to know if it's considered best standard practice and approved by pump manufacturers & local codes.

I do trust that the experts on this site are experienced & confident in their abilities to properly / safely install a submersible pump in open water, and hope this thread has provided an opportunity for learning; it certainly helped me.

Jamie Hall

I suspect that indeed at least one or two of us were mislead — I certainly was! But for reference, I've been playing with irrigation systems (and snow making installations — not all that different, in some ways)— off and on — for the last 60 years or so, among other things — but mostly rather larger ones (Cannon Mountain, New Hampshire, was my first effort — back in 1966)! The only irrigation system around here which I had a hand in was (other than residences and hobby farms) a very nice system, drip irrigation for vegetables on about 25 acres. Three submersibles in the adjacent river; I'd have used self-primers there, but there was a noise concern.

hot_rod

when you start getting into well pump sized submersibles, 10 gpm and up they start to get $$. Plastic body above ground well pumps are reasonably priced.

I would look into one of the ECM pressure booster pumps. Efficient, safe, and whisper quiet. It would need to be protected in an enclosure

EBEBRATT-Ed

Swimming pools all have pumps and the water is conductive even if the piping is all plastic