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Discussion Starter · #1 ·
Alright... I'm lost on this. Can someone fill me in on what the numbers mean? I'm trying to figure out how well my system is setup for the irrigation package and especially right now, the total head i'm pulling from the drop pipe to my creek (i'm having issues right now with the low creek level and drought we're having in western Montana).

I asked a local irrigation ag company and they were just like... "you have a 2 1/2, ya you're fine with up to 9ft of head at our elevation of 3400ft above sea level". Ok... not that I don't trust them. I just want to understand. What do those numbers mean and how do I figure out based on the elevation of my drop pipe's static water level, to the pump itself if i'm setup right?

163059


... powered by a 15hp GE 3 phase motor.
 

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Discussion Starter · #3 ·
Is 9 ft the maximum suction lift for that pump?
No clue. The local ag irrigation company literally just wanted to know: "Is that a 2 1/2 pump head or 3 1/2. Oh, it's a 2 1/2? Well then, you can suck a good 9' feet at least".

I've spent 12 hours now trying to figure out the issue (primes, starts, won't build vacuum pressure on the switch) and am starting to be convinced, the guy is completely wrong.
 

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Discussion Starter · #4 ·
FYI: My setup. Just so everyone can see it. Creek water is about 6ft below the pump inlet. Lots of water in the cistern (4ft). 5" pipe. A single 90 elbow atop the cistern. I just want to validate i'm not fighting physical limitations of the pump here. Normally that water level is 2ft higher at least.

163062
 

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Discussion Starter · #6 ·
Do you have a foot valve on the end?
No... it's wide open with a large basket about 4ft under water, which I have cleaned. There is a reverse flow / check valve to the right of the pressure gauge pictured. Then, it's just wide open 5" pipe over flat ground, to the pivot center 688ft away.
 

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Discussion Starter · #7 · (Edited)
So, turns out Cornell (in Oregon) is super responsive. Didn't expect to hear back, but I did just a minute ago.

The 2 1/2 numbers represent the discharge in inches.
The W is just the style/model of the pump.
The "Trim" is NOT the trim of the impeller like on a boat prop, it's the actual diameter of the impeller in inches.
The 15 is the HP it is to be coupled with.
The -2, indicates it is to be a 2 pole motor.

Specs on the pump. TDH, like 200ft. LOL Ok, so that's not my issue. I still have questions about ag pump setup in general if anyone can help educate me. General, how does it work kinda questions like...


When I prime it with the pump handle, I am creating vacuum in drop pipe? This of course pulls the water up and I do this until I get a half gallon or so squirting out the primer discharge port. There is a pressure switch, which appears to require a CLOSED circuit to function. I say appears, but in reality I know it does. Open = pump off, closed = pump on. Is the switch picking up vacuum on the pump inlet or is it picking up pressure on the discharge? Should I be priming the system to the point that pressure switch is tripped without the pump running? Will the pump have a better chance of starting to create pressure on a dead-head or with the discharge gate valve slightly cracked?


What really causes a pump to push water / create pressure vs. the failure i'm experiencing of it not doing so? I never really totally understood the inner workings of the thing and now I kinda have to or pay someone else to trouble-shoot cause i'm out of ideas.
 

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So, turns out Cornell (in Oregon) is super responsive. Didn't expect to hear back, but I did just a minute ago.

The 2 1/2 numbers represent the discharge in inches.
The W is just the style/model of the pump.
The "Trim" is NOT the trim of the impeller like on a boat prop, it's the actual diameter of the impeller in inches.
The 15 is the HP it is to be coupled with.
The -2, indicates it is to be a 2 pole motor.

Specs on the pump. TDH, like 200ft. LOL Ok, so that's not my issue. I still have questions about ag pump setup in general if anyone can help educate me. General, how does it work kinda questions like...


When I prime it with the pump handle, I am creating vacuum in drop pipe? This of course pulls the water up and I do this until I get a half gallon or so squirting out the primer discharge port. There is a pressure switch, which appears to require a CLOSED circuit to function. I say appears, but in reality I know it does. Open = pump off, closed = pump on. Is the switch picking up vacuum on the pump inlet or is it picking up pressure on the discharge? Should I be priming the system to the point that pressure switch is tripped without the pump running? Will the pump have a better chance of starting to create pressure on a dead-head or with the discharge gate valve slightly cracked?


What really causes a pump to push water / create pressure vs. the failure i'm experiencing of it not doing so? I never really totally understood the inner workings of the thing and now I kinda have to or pay someone else to trouble-shoot cause i'm out of ideas.
That is a pressure switch for the discharge. By priming the pump you are creating a vacuum pulling the water thru the pump and getting the air out of the system. Once you have all air out you want to turn it on with discharge gate valve slightly cracked, if too far open it will cause pump to cavitate and break suction. If done correctly the pressure in pump will immediately jump up which will then close the pressure switch. For power to even start the pump you need to either have a bypass switch for the pressure switch or manually hold the pressure switch in the closed position while starting. Why the pressure switch is there is so the pump will not run when dry thus destroying the packing or more.
 

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Discussion Starter · #9 ·
If done correctly the pressure in pump will immediately jump up which will then close the pressure switch.
This occurs, but the switch immediately re-opens / loses pressure. I was trying to dead-head start it (i've been doing this all summer and it's worked fine till now) slowly start opening the discharge gate valve after I validate it stays running. I'll try some more tonight with the discharge slightly cracked, though i'm pretty confident i've tried that about 40-50 times in the last 2 days as well with no luck. I'm starting to think the problem might be discharge leak.

Also, there's a ball valve below the primer pump. I shut that off before I try and start it. That ball valve leaks a tiny bit though it's not been an issue till now. Guess i'll replace it. Ya, it's setup with a start/man switch/button combo so i'm only messing with the pressure switch/looking at it to trouble-shoot.
 

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I know I have had setups with 1-inch pumps and I had to put a foot valve on the end to trap the water in the intake tube. I would fill the entire tube and pump full, Once I had all the air out it would pull water through the pump and hold prime. any air would not create enough suction to bring the water all the way up to the pump. I would be running the pump and be pulling the vacuum until the pump had a solid bite on the water and expelled all air, the momentum will take over and the pump will feed itself. it is just a little too much to ask to bring it up that far but once you can get it there it will run. Can you manually engage the motor and pump the vacuum at the same time?
my neighbor pulled water from a 60ft deep well that way when everybody said it couldn't be done that far, mind you the output was a lot lower.
 

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Discussion Starter · #11 ·
I know I have had setups with 1-inch pumps and I had to put a foot valve on the end to trap the water in the intake tube. I would fill the entire tube and pump full, Once I had all the air out it would pull water through the pump and hold prime. any air would not create enough suction to bring the water all the way up to the pump. I would be running the pump and be pulling the vacuum until the pump had a solid bite on the water and expelled all air, the momentum will take over and the pump will feed itself. it is just a little too much to ask to bring it up that far but once you can get it there it will run. Can you manually engage the motor and pump the vacuum at the same time?
my neighbor pulled water from a 60ft deep well that way when everybody said it couldn't be done that far, mind you the output was a lot lower.

All good advice. I wonder if i've always had issues (my pump HAS always been hard to start, taking a solid 15 minutes of trial error) and now with the creek at a record 2 ft lower, it's just got no tolerance for some air pockets etc.

Ya, I could absolutely have the wife hold the start button on the panel while I'm pumping. Only thing is, that means the ball valve for the primer pump will be open instead of closed. I actually suggested I try this to some local veteran rancher farmer guy last night on the phone. He was like, no don't ever do that. LOL Whatever... can't hurt.
 

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More than likely you have air getting in on the intake side. Need to find that first before it will work easily. On my centrifugal pumps I got rid of the priming pump by putting a foot valve in the intake and using a water tank to fill the pipe and pump. Now super easy to start. Again though you can't have an air leak on the intake.
 

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Discussion Starter · #13 ·
More than likely you have air getting in on the intake side. Need to find that first before it will work easily. On my centrifugal pumps I got rid of the priming pump by putting a foot valve in the intake and using a water tank to fill the pipe and pump. Now super easy to start. Again though you can't have an air leak on the intake.
Appreciate that! I'll check all that very carefully. Maybe just replace the inexpensive seals on the intake side where it goes from a 5" pipe to my 2.5" inlet pipe / bell reducer, plus check for tight etc.

On the foot valve, I guess i'm just concerned that I will never be able to lift the pipe up out of it's cistern when it's full of 500lbs of water.
 

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On foot valves they have a 3/4" plug right above the flapper, you just drill a hole in the plug (which is under water) and it will drain the intake down to the water level. We have 30' + long 8" pipe for our intakes and it works well on them.
 

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The impeller in these centrifugal water pumps is the key to it pumping. Some of these pumps like a 2 or 3” Banjo will self prime at a few feet of lift. Others like a shallow well jet pump will never self prime. The impellers just do not create vacuum in air. That is why the system you have has the hand primer to get all the air out except maybe a tiny air pocket trapped in the upper part of the scroll. Even that can be enough air that the impeller will lose grip on the pure water coming in the suction side. I had to drill a hole in the top of the scroll, where your pressure switch mounts, and bleed the air out of there before the pump would make pressure. I’m thinking you could try to hook up a small 1/4” line from a T installed below your pressure switch to your hand vacuum pump inlet. That is how critical having no air in the impeller housing can be. I would agree with a couple of others in suggesting you have a foot valve or a ball valve in the suction pipe to keep it right full of water between uses. That allows you to pour water in to fill the suction pipe and impeller housing. Any tiny air leak on the suction side will over time create an air bubble that will cause priming problems between uses. Your hand vacuum pump should overcome that though. Back to fix all the air leaks and maybe a foot valve in the water at the bottom of the suction line. Good luck!
 

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We use vacuum pumps to ease priming on our irrigation pumps, but the principle is the same as a hand primer. We dead head the pump, prime them, then turn them on and crack the valve slowly to about 4 notches out of 10 and leave it there until the pivot is filled. Some low pressure machines I open it about 2/3 and wait until the sound of the pump changes before opening it the rest of the way. Usually when I crack the valve slowly, the pump catches right away. Open too fast and it will lose it.

On our pumps instead of that pressure switch we use a murphy pressure gauge. The only advantage is it can give you a psi reading as well as shut the pump down when it loses prime. PSI gauge is a sure way to know you've got the pump caught. Most of our panels have OFF-AUTO-HAND knob. In the HAND position the pump turns on regardless of the pressure switch or the pivot kill status. This is only for starting. After priming and the pivot is running, it is switched to AUTO.

Hard priming is always because of a vacuum leak. Our pumps all have rubber boots that connect the pump to the intake. Sometimes the boot cracks and lets air in. Sometimes the butterfly valve on the output isn't sealing (or the output check valve if you have one). Or could be the packing. If everything is as it should be you can prime it, close the valve to the primer, and the water should stay up in the pump for a while. Sometimes you can listen for air hissing to find a leak.

With my vacuum pumps, I prefer to suck from the intake rather than higher up on the output side. That way I can use the vacuum pump to hold the prime if I'm having a hard time getting the pump to catch. But for a hand primer it's probably best to suck from as high on the volute as possible, so what you've got is fine. Although having said that, my neighbor prefers to put his hand primers on his suction side also because then he can fire up the pump and if it doesn't catch right away he can pump it with the hand primer while the motor is still running. You can't do that as easily when the primer is on the discharge side.

I like the idea of the foot valve. My neighbor is converting all his pivots to pump out of gravel wells he's building into his ponds, and at the bottom of the intake puts the special foot valve. Basically it's a two-flap check valve that doesn't restrict the water flow. Says it will hold the column for weeks usually. Makes turning on the pump super simple (and he often does it remotely). When winter comes they have a rod they installed that pulls the check foot valve thing open. No more pulling intakes. I'm going to do this to my pumps too. I'm tired of fowled screens.
 

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Discussion Starter · #18 ·
Man I really appreciate everyone's time and replies! So incredibly helpful!


I had to drill a hole in the top of the scroll, where your pressure switch mounts, and bleed the air out of there before the pump would make pressure. I’m thinking you could try to hook up a small 1/4” line from a T installed below your pressure switch to your hand vacuum pump inlet. That is how critical having no air in the impeller housing can be.
Hard priming is always because of a vacuum leak. Our pumps all have rubber boots that connect the pump to the intake. Sometimes the boot cracks and lets air in.
2 key bits of info here!

1. I really like the idea of having a bleeder atop the pump housing near the pressure switch. This makes a lot of sense to me! Probably would help, but wasn't my actual issue.

2. Exactly what you / others said. This was a vacuum leak and it was surprisingly difficult to find until I broke something.


All Fixed!
The issue was (and probably has been since i've owned this setup), a hairline crack in the riser / nipple that the hand-pump is located atop of. I've always had a ton of difficulty priming this pump. Normally it's a 20 minute ordeal minimum to start it and without much prior experience, I just thought... well... old equipment pump. Turns out, I was never getting rid of all the air priming it. The crack was developing on the back side where I couldn't see just below the ball valve to the hand pump. I was pushing tons of water out, but never really getting good/perfect vacuum in the pump housing. My "Manual" setting on the switch doesn't work / isn't wired right. So, i never had the ability to have the pump running while priming. I did this with help, and bam! Pump primes but won't hold it's prime. Progress!

Then I got angry and started just pumping like a mad-man and that's when I discovered the crack as the nipple broke in half right below the ball valve. Interesting I thought... maybe this was cracked all along? Pipe threader, new valve, 1 hour later I'm pumping 6-10 pumps and hitting the switch with a holding prime, every time! Couldn't be happier!
 

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The cracked valve was probably caused by a bit of water sitting above the closed valve in winter. Even after the pump got drained!
 

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Discussion Starter · #20 ·
The cracked valve was probably caused by a bit of water sitting above the closed valve in winter. Even after the pump got drained!
Ya, that's a good point. It's in a little pump house, but the sides are open for ventilation and definitely would get blowing snow all over it. I think i'll take some boards and cover it up this fall + throw a bucket over the pump valve. Of course, i'll take/spin the hand pump off for the winter.
 
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