The check valve discussion.

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Rshackleford

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I think you have to consider that magic 32’. I would say that the column of water would probably fall if it is unchecked for a distance greater than this. A good question would be when does this vacuum become a hazard for the drop pipe.

Also, what about multiple checks in the drop pipe when setting a deep sub. I think they recommend one ever 200’ or 300’.
 

Bob NH

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speedbump said:
If the droppipe has no leaks what so ever, there is no check valve in the pump or anywhere in the droppipe but there is one at the top of the well to hold the pressurized side of the system there. The water level is lets say 100 feet. The pump shuts off, what is going to hold that water up in that column of droppipe. I say there will be a vacuum created from the top of the pipe down to around the theoretical 32 feet. If the water level in the well is say 15 feet, then the water can drop to that depth or somewhere in between depending on the physics that I can not explain.
bob...
A vacuum is just the absence of pressure. Atmospheric pressure of 14.7 psi in the well will push on the water in the top of the well, forcing it through the pump to an elevation of about 14.7x2.31=34 feet above the level in the well.

Therefore, if the check valve is more than 34 feet above the static water level in the well, then the water will drop down to 34 feet above the static level, creating a vacuum in the upper portion of the droppipe. It works the same was as a mercury barometer. (There is actually a small pressure above the water in the drop pipe equal to the vapor pressure of the water.)

If the check valve is much higher than 34 feet above the static water level, then when the pump shuts off the check valve will stop the reverse flow from the pipe above the valve, but the weight of the water between the pump and the valve will cause a reversal of flow through the pump, actually causing it to rotate in the reverse direction. I saw one installation where the check valve was at the top of a hill and the pump was a turbine pump in a pumphouse. It was possible to both see and hear the effect of the reversal of flow. It is especially bad if the pressure tank/pressure switch causes the pump to restart when the pump is rotating in the reverse direction.
 

Rshackleford

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The reverse flow thing is a big deal on line shaft turbines since there is no way to put a check on them. However bad this situation is we have never had a customer twist off a shaft, though. We do install some on delay timers when automation makes restarting a risk, but not very often. I guess that must be part of the reasoning behing NRR heads on motors and gear drives.
 

hj

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speedbump said:
I disagree HJ, if the droppipe has no leaks what so ever, there is no check valve in the pump or anywhere in the droppipe but there is one at the top of the well to hold the pressurized side of the system there. The water level is lets say 100 feet. The pump shuts off, what is going to hold that water up in that column of droppipe. I say there will be a vacuum created from the top of the pipe down to around the theoretical 32 feet. If the water level in the well is say 15 feet, then the water can drop to that depth or somewhere in between depending on the physics that I can not explain.

Make sense?

No, but if it did, then when you stick a straw into a glass of water and hold your finger over the end and then pull it out, according to your "theory" the water would drop down to the level of the water in the glass. But it doesn't. And when I want to start a siphon, I immerse the hose in the water, hold my finger over the end and then pull it up and over the rim of the sink and place it in a bucket. Again, if your "theory" were correct the water would drop back down in the hose and thus not start the siphon. And water heaters would never have to be given an air input source to drain the water out of them because it would always drop down to the level of the drain valve.
 

almostdone

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HJ -

I'm just a science teacher, but the theory proposed is correct. The reason that you don't run into the problem of water draining out of your siphon hose is that atmospheric pressure is adequate to hold up a column of water that is 32 ft high. If you filled the hose with water and then climbed up 40 ft, you'd find that the water would drain from the hose down to the 32 foot level, despite the fact that no air was leaking around your finger.

BTW, this is why an old style leather-flapped single piston pump won't work for a deep well. You can't rely on atmospheric pressure to push the water to top of the well, so you have to "throw" the water to the top of the well with an impeller.

DM
 

Rshackleford

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Almostdone is right about Olson Johnson being right. I wash born here, an I wash raished here, and dad gum it, I am gonna die here, an no sidewindin bushwackin, hornswaglin, cracker croaker is gonna rouin me bishen cutter.

I am quite interested in the comment on the piston style pump. Are we talking about cylinder pumps with leather cups. I was not aware that there was a depth limitation on these pumps.
 

Speedbump

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This thread gets better all the time. Since I am not edjumicated and only have experience to rely on, I can attest to the fact that a piston pump will only lift water somewhere around 25 feet. I believe they will go a little better than 25 feet depending on elevation etc. But because of the positive pull a cup leather makes over an impeller, the vacuum created is better. They can make some horrendous pressures too. I saw a 42 gallon tank that launched because of a plugged pressure switch. The bottom blew out sending the tank to the ceiling of the basement, which broke two floor joists (2X6's) pushed the kitchen floor up high enough to break the counter top and ruin everything glass in the entire kitchen. I feel much safer standing next to a jet pump now.

I have seen a few unscrewed deep well turbines and have fished a few. But you can put a foot valve under a turbine. Most are installed that way here in these parts. I have also seen shafts twisted off from the back spin of the water going back due to a faulty or missing foot valve; then the motor starting while the pump was counter rotating.

bob...
 

Rshackleford

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I had never though of putting a check valve on the bottom of a line shaft turbine. We have lots of irrigation wells up here with only checks on the discharge.

Give me an example of one of these piston type pumps, please? I assume this is not a cylinder pump under a windmill.
 
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Speedbump

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These are the best images I could find of a piston pump. Since they are like hens teeth these days.

Forget the attatchments, they don't work. Maybe .bmp files won't work.

I'll try after I convert them to .jpg's.
 
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Pumpman

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I used to work for a geothermal power company as a well field spe******t. We installed lineshaft turbine pumps as deep as 2000', and most of these wells had a static water level from 600' to 1000' below top of well. There were no checkvalves anywhere in the column pipe. There was one located about 40' downstream of the discharge head.
When we would start these pumps, it would take anywhere from 20 seconds to a minute for the water to reach the surface. This tells me that the water level in the pump column pipe was somewhere near the static water level of the well. If the column stayed full, it wouldn't take any time for the water to reach surface. There were no vacuum breakers etc. on the systems.
Ron
 

Speedbump

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They were the predecessor to the jet pump. I worked on many of them. There I go gelling my age.

They were really a very good pump. The working head pump was used like a windmill rig with an electric motor for deep well apps.

bob...
 

Speedbump

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The pipe must have been large enough to keep the water from hammering the valve I would think. Did it have any hammer to it when the water column reached check valve.

Did you cuss there Ron? I see the profanity police put asterisks in your word that I would think was spe******t.

bob...
 

almostdone

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Off topic, but that's pretty funny. I thought there was some deep inside water well business joke that caused Ron to bleep out part of spe******t, but it turns out that the spam filter is just picking up that well-known drug for ED: ******.

Now, I'll spend the rest of day trying to figure out words that contain the magic letters ****** and ******.
 

Speedbump

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Is it that drug that is advertised on TV and radio, that proports enhancement of sorts? I'll spell it and see what I get ******.

bob...
 

Pumpman

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Nope, I didn't cuss. Drat that spam filter anyway. haha
Yes, actually, the checkvalve (10") slammed open with a bang. The pressure would immediately raise to 225 psi on startup, and level out out to 310 - 350 psi while running. Since the geothermal brine was 340 degrees, you didn't stand too close to the piping when you brought one of these pumps on line. We frequently ran these pumps to an open pit until the brine came up to temp, before we sent it to the plant. The sound of the hot brine flashing into steam at the pond would take your breath away. Like standing behind a jetliner as it preps for takeoff.
Ron
 

Speedbump

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Now that would be something to see. I have never had the opportunity to do any of that kind of work. But I would love to see it.


bob...
 

Rshackleford

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On the piston pump, I though you guys meant cylinders for windmills. I know they can go more than 25’ feet.

On the turbines, “soft start†pump have made a big difference. Some of these wells with 100’ static’s would really hammer the check valves bad. We would always put a butterfly right on the pump head. Then this valve could be closed way down to prevent some of that hammer. I have seen discharge systems blown apart by careless well owners.
 
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