Well Water System Design

[Raspy]

Harry,

I'll try again.

I'm not advocating the use of check valves. This is just an explanation as to why they are used when they are used, as far as I understand it.

Obviously, the pump is immersedand there is no suction on it's intake side. Let's get beyond that.

Now, imagine a system with the pump down in the water. The stand pipe to the surface is open and the distance to the surface from the standing water line is much farther than 30 feet, say 300 feet. We turn on the pump and water gushes out at the surface. Then we close a valve on the pipe at the surface and block the flow. Then we turn off the pump and what happens?

The atmospheric pressure down in the well is not sufficent to hold the column of water at 300' elevation. The water level in the pipe drops to about 30' above the water level and holds there.

The void in the pipe above the water is not air or a "cushion", as you mentioned. It's an empty vacuum.

Now we have about 270' of empty pipe. The key is "empty". No air. Not a cushion. This where the word suction was used in my previous blurb. A high vacuum area, if you will.

Now we turn on the pump and the water rushes up the pipe. Remember, no cushion, and slams into the closed valve. This caused an instataneous pressure rise that can break the pipe or just jar the whole system.

However, if there were check valves at every 25', there would not have been a void at all.

Again, I'm not saying they are needed in yours or any system. Each one is different and can be arranged in many ways.

The pressure tank is not necessarily useful in this case because the closed valves could be beyond or before it and the configuration can still cause a hammer. When there is this kind of vacuum, the diaphragm tank has zero volume because the bladder is pressed agains the connetion port. Sometimes the tank port is quite small and the tremendous pressure hit is more than it can handle to prevent a hammer.
Some systems can sit for months, unused, and this condition can gradually develop.

Do you see the difference between this scenario and the initial startup when the system is full of air? An air cushion vs an empty pipe? Not the same thing at all.

 

[TheGoose]

I posted it once, I'll post it again, you should never install check valves every 25' in any submersible pump system. If you really want to install check valves, the mfg's suggest to do it every 200', not every 25' like suggested. I'm not even sure how you would install a check valve every 25' when pipe is either 20' or 21' in length, and with poly you want one single piece all the way to the pump if possible.

The reason is that if one single check valve in that line fails, it can cause water hammer. Multiple check valves give more opportunity for failure. In fact, if one single check valve in the column fails, more than likely the rest will fail soon after due to the water hammer effect coming from below. You compound the problem by adding more check valves.

The only check valve in the system should be installed just above the pump discharge or built into the pump itself. Good quality pumps, like Goulds, can have check valves that last 20+ years. If the check valve fails before the pump does, the pump needs to be pulled and the check valve replaced or repaired. I normally remove the built-in and install a MXF check valve that screws directly into the pump discharge and the drop pipe screws into it if I have a failure on a newer pump.

The exception to the checkvalve rule is on a system with an air maker installed, which uses a check-valve at the surface with a vacuum breaker and bleeder down in the well to make air to feed into a hydro-pneumatic tank.

Rope is more likely to become entangled with the pump and lock it in the well many times more than it is used pulling a pump out. Hang a pump on good quality pipe such as sch 80 or steel and you'll more than likely never have a problem. Even on a 4.5" casing the pump diameter is almost 4" (3.9" diameter) which doesn't leave but .25" on each side for something to wedge in there and lock it in place like chinese handcuffs. 4" wells are even tighter.

I have installed hundreds of submersible pumps, some have lasted 20+ years. Use good quality materials, take your time, and talk to your driller and see what works best for your area.

Good Luck.

 

[Egon]

Just fix the bottom pump check. Solve all your problems as well

as keeping the pipe from collapsing.

Just how do you get 300 ft. Of vacuum.

 

[turnkey4099]

Harry,

I'll try again.

I'm not advocating the use of check valves. This is just an explanation as to why they are used when they are used, as far as I understand it.

Obviously, the pump is immersedand there is no suction on it's intake side. Let's get beyond that.

Now, imagine a system with the pump down in the water. The stand pipe to the surface is open and the distance to the surface from the standing water line is much farther than 30 feet, say 300 feet. We turn on the pump and water gushes out at the surface. Then we close a valve on the pipe at the surface and block the flow. Then we turn off the pump and what happens?

The atmospheric pressure down in the well is not sufficent to hold the column of water at 300' elevation. The water level in the pipe drops to about 30' above the water level and holds there.

The void in the pipe above the water is not air or a "cushion", as you mentioned. It's an empty vacuum.

Now we have about 270' of empty pipe. The key is "empty". No air. Not a cushion. This where the word suction was used in my previous blurb. A high vacuum area, if you will.

Now we turn on the pump and the water rushes up the pipe. Remember, no cushion, and slams into the closed valve. This caused an instataneous pressure rise that can break the pipe or just jar the whole system.

However, if there were check valves at every 25', there would not have been a void at all.

Again, I'm not saying they are needed in yours or any system. Each one is different and can be arranged in many ways.

The pressure tank is not necessarily useful in this case because the closed valves could be beyond or before it and the configuration can still cause a hammer. When there is this kind of vacuum, the diaphragm tank has zero volume because the bladder is pressed agains the connetion port. Sometimes the tank port is quite small and the tremendous pressure hit is more than it can handle to prevent a hammer.
Some systems can sit for months, unused, and this condition can gradually develop.

Do you see the difference between this scenario and the initial startup when the system is full of air? An air cushion vs an empty pipe? Not the same thing at all.

Okay, you dropped the "suction" which is what I have been on about. As for your 300' of empty pipe: How come you have a malfunctioning foot valve? That is what keeps the water in that 300' of piple, not atmospheric pressure. Also that "rush of water slamming into that valve: What valve? there is no need for any valve between the pump ( submersibles have one built in) and tank except perhaps a shut off that should always be open unless maintenance is being doen. Even if there _is_ a check valve, your 'sudden pressure spike would apply at it and all subsecquent ones.

Your system, do it how you want. I will add, though, that if a well diller/installer told me to put in multiple check valves I would be looking for a different installer.

Harry K

 

[turnkey4099]

Just fix the bottom pump check. Solve all your problems as well

as keeping the pipe from collapsing.

Just how do you get 300 ft. Of vacuum.

I was wondering the same thing.

Harry K

 

[sailfast]

Harry,

I'll try again.

I'm not advocating the use of check valves. This is just an explanation as to why they are used when they are used, as far as I understand it.

Obviously, the pump is immersedand there is no suction on it's intake side. Let's get beyond that.

Now, imagine a system with the pump down in the water. The stand pipe to the surface is open and the distance to the surface from the standing water line is much farther than 30 feet, say 300 feet. We turn on the pump and water gushes out at the surface. Then we close a valve on the pipe at the surface and block the flow. Then we turn off the pump and what happens?

The atmospheric pressure down in the well is not sufficent to hold the column of water at 300' elevation. The water level in the pipe drops to about 30' above the water level and holds there.

The void in the pipe above the water is not air or a "cushion", as you mentioned. It's an empty vacuum.

Now we have about 270' of empty pipe. The key is "empty". No air. Not a cushion. This where the word suction was used in my previous blurb. A high vacuum area, if you will.

Now we turn on the pump and the water rushes up the pipe. Remember, no cushion, and slams into the closed valve. This caused an instataneous pressure rise that can break the pipe or just jar the whole system.

However, if there were check valves at every 25', there would not have been a void at all.

Again, I'm not saying they are needed in yours or any system. Each one is different and can be arranged in many ways.

The pressure tank is not necessarily useful in this case because the closed valves could be beyond or before it and the configuration can still cause a hammer. When there is this kind of vacuum, the diaphragm tank has zero volume because the bladder is pressed agains the connetion port. Sometimes the tank port is quite small and the tremendous pressure hit is more than it can handle to prevent a hammer.
Some systems can sit for months, unused, and this condition can gradually develop.

Do you see the difference between this scenario and the initial startup when the system is full of air? An air cushion vs an empty pipe? Not the same thing at all.

I recommend you get out a physics book and do a little research.

 

[turnkey4099]

I recommend you get out a physics book and do a little research.

And talk to an installer/driller who knows his trade.

Harry K

 

[Pettrix]

Spoke to the driller today. He said that he recommends a 10gpm pump with two 85 gallon pressure tanks with a sediment filter installed prior to the tanks. The main shutoff valve should be installed AFTER the pressure tanks. He said that 2-3 check valves will be installed in the system. The 1" PVC 40 sch pipe is more than adequate for my setup and according to him that 2' is more than deep for that area for freeze protection.The 1" PVC pipe would then transition into a PEX line that would come up through the slab.

He also recommended doing the well prior to breaking ground so that the construction crew can have on-site water for use in soil compaction and concrete work. He said that they can setup the well to run off of a generator with the pitiless adapter and hose spicket.

 

[turnkey4099]

I did a bit of googling for multiple check valves. Turned up one engineer who had written a paper recommending them but IIRC the article specified one for a 600 ft well. Reviews ofthe article by professional well drillers, installers were all negative.

Granted I didn't spend much time at the search so...

Harry K

 

[TheGoose]

From Franklin's Installation Manual:

http://www.franklin-electric.com/media/documents/60Hz_AIM_05-06.pdf