Well Advice Wanted

[TVL]

I have posted here in the past and I have always received good advice. So, long story short:

I began having well issues in spring of 2013 - 4" PVC - 141 foot deep sand well - drilled in 1978 - static water level approximately 118' - used for irrigation system only
Suspected pump was going bad and had it replaced .......... the impellers were almost completely destroyed
That took care of pump issue, but replacement pump quickly pumped well dry (and yes, pump was the exact same size and specs as original)
Lowered pump from 132' to 137' with no relief. This located pump just a few inches off bottom of well
Attempts to clean 141' well by having it "blown out" were unsuccessful in restoring yield - however, the "blow out" did completely clean out the inside casing, so pump then hung about 4 feet off the VERY bottom of the casing ........... but well still could not provide the normal yield
So, I had a new well drilled just 15 feet away
New well ended up being 145' with a static water level of 117' 9", so I am assuming it is in the same aquifer as the original
Submersible pump hangs in the new well at a depth of 142' - I also had 1/4" tubing & gauge installed so I could constantly monitor water level
In the very BEGINNING, the static water level would drop approximately 13 feet while the irrigation system was functioning. This put the pump about 11 feet under water during operation and 24 feet while resting. The new well appeared to be doing its job!
The static water level drops very little now and I'm assuming it's because the well has further developed itself. The past two years as shown the static water level only drops approximately 2.5 feet during irrigation ..... and I monitor this almost daily!

So, here is what I would like to know:

1- Most importantly: the next time the pump is pulled, would it be acceptable to raise the pump so that it hangs at a new depth of approximately 135 feet. This would put the pump 10 feet off the bottom instead of just 3 feet. Current drawdown would ensure the pump is under at least 14.5 feet of water at all times. At the current depth of 142', I am not 100% sure the motor is getting proper cooling. Maybe so since this is a bottom feeding well, but it just seems to me that is a little too close to the bottom. Then again, maybe there are other valid reasons for NOT raising the pump ............ what are your thoughts?

2- The first well did so good for many years. Is it LIKELY the issue that caused the well to quit yielding properly was nothing more than sand clogging the well screen over the years?

Thanks everyone!

 

[Texas Wellman]

I'm not sure I fully understand the situation. Here we have screens, so the last 10' or so feet would be a screened area and if you could put the pump in the screen you would not be receiving the full cooling across the motor. As long as the water is feeding from under the motor I assure you it's cooling it.

 

[Sponsor]

 

[TVL]

Texas Wellman: Both wells had screening like that shown in the attached link. As a matter of fact, the bottom two 20 foot sticks were like this. So, in reality, I had 40 feet of screen. Both the driller in 1978 and the one in 2013 estimated the sand aquifer was approximately 40 foot in depth, therefore 40 foot of screen was put down. And yes, I was there when it was done and saw the 40 foot of screen placed in the bore hole.

1- I would like to raise the pump so that it isn't so near the bottom. But, in doing so, I don't want to introduce an issue that I wasn't aware could occur.

2- If the SAND aquifer is indeed 40 feet in depth, I'm not so sure that the majority of water flow is coming from the very bottom where the pump now sits. Obviously some flow is coming from that depth or I would have had heating issues by now ............ at least that is my thinking! I'm simply thinking that if I raise the pump as described in my original thread, I will therefore guarantee the pump motor gets better cooling if it is indeed not getting adequate flow where it now hangs near the very bottom. But again, will raising the pump have an affect I haven't considered?

3- The pump was originally placed near the bottom because the driller felt I needed all the head I could get. This was based on the issues I was having with the original well as mentioned in my original post.

 

[Smooky]

My guess is the bed rock is 145 foot deep and your well driller only does gravel pack wells. I would not have bored two gravel pack wells within 15 foot of each other. Have you considered putting in a drilled well?

 

[TVL]

My guess is the bed rock is 145 foot deep and your well driller only does gravel pack wells. I would not have bored two gravel pack wells within 15 foot of each other. Have you considered putting in a drilled well?

Isn't this a drilled well I now have?

The first well is no longer in use .............. so, what harm was there in putting a new well close by?

In this part of SC there are MANY sand wells just as I now have. My first well lasted 35 years. Sand wells don't sound to bad to me unless I am missing something???

 

[Smooky]

No harm in drilling two side by side except for the cost. My guess is the water level has dropped for some reason. It is kind of like putting two straws in an empty glass, it is no harm but you can only suck so much water out of that hole /area. With the water level being down 117 feet and with the wells bottoming out at 145 that does not give you a lot of reserve. With a slight drop in the water table it could affect how much you can pump before the water level drops below the pump. A gravel pack is only in the soil that is above the bedrock. A drilled well has a solid steel or PVC casing from the ground surface down to the bedrock. All the surface water is sealed off. After the casing is set and pressed into the top of the rock a smaller usually 4"rock drill is is lowered down to the rock through the casing. The casing is usually 6 inches. A 4" hole is drilled into the rock to what ever depth is necessary to get enough water and set the pump. In your case the casing may be 150 feet or so before they start drilling into the rock. In NC there are a lot of gravel pack wells east of hwy 95 but very few west of hwy 95. Mostly in the piedmont and in the western part of the state they have drilled wells. Drilled wells can go down to 800 foot or so. There are still a lot of large diameter bored wells too. The bored wells are usually less than 100 foot and often go dry in the summer.

 

[TVL]

With the water level being down 117 feet and with the wells bottoming out at 145 that does not give you a lot of reserve.

Thanks for replying Smooky!

There is one point I would like to bring to your attention. The static water level in my original well was about 118 feet. The static water level in the new well is 117' 9". The water level has remained the same for 35 years. The original well was initially able to provide 25+ gpm with no issues. I'm thinking the screen became plugged over the years.

Anyway, thanks for your response.

Now, I'm hoping my original post can get additional attention and possibly get the two questions answered. Thanks again everyone!

 

[Craigpump]

Why would you want to change something that is working just fine?

 

[Valveman]

When you have 40' of perforated pipe in the bottom of the well, the only way to make sure the water is flowing past the motor is to set the pump above the perforated pipe. You don't have enough standing water to do this. That is why we use 5" or larger casing. That way we can install a 4" shroud or flow inducer over the pump/motor. It will still fit inside 5" casing and we can set the pump a foot or two off the bottom. With 4" casing you don't have that option.

Having said that, the motor company says that 2HP and smaller motors are so short that they do not need a shroud to get adequate cooling. This should be taken with a grain of salt, as motor companies like to sell more motors. While this maybe somewhat true, especially when your old motor lasted so long, I still prefer to have a shroud or set the pump above the perfs to make sure the motor gets the most cooling flow possible.

 

[TVL]

Why would you want to change something that is working just fine?

No, I surely don't want to screw up things since everything appears to be working correctly.

But, it has been stated many times on this board that a pump should NOT be placed near the very bottom of a well. And that is where my is located, very near the bottom .............. 2 to 3 feet from the bottom.

My reasoning for possibly wanting to raise the pump is that unless my well feeds from the very bottom of the sand aquifer, the pump probably isn't getting the best water flow across the motor. And, with a 40 screen and supposedly a 40 foot deep sand aquifer, how likely is that almost all water is flowing upward from the bottom 3 feet of the well casing?

Anyway, I will do what the majority feels is best in my situation. Ya'll are the experts!

Thanks again!

Craigpump: I'm assuming that you feel since I've had no issues with the system as it is (pump near bottom & no pump issues as of yet because of overheating), everything must be OK. I'm also assuming since you are aware the pump is very near the bottom, you still feel the motor is getting proper water flow across the motor and this should not be a concern for me. If so, I will respect that since it is coming from an expert. However, I still hope a couple of other experts will also give their opinion to see if this is what the majority agrees upon. I simply want to do what is correct for the long-term and make a change if it is deemed advisable!

 

[TVL]

When you have 40' of perforated pipe in the bottom of the well, the only way to make sure the water is flowing past the motor is to set the pump above the perforated pipe. You don't have enough standing water to do this. That is why we use 5" or larger casing. That way we can install a 4" shroud or flow inducer over the pump/motor. It will still fit inside 5" casing and we can set the pump a foot or two off the bottom. With 4" casing you don't have that option.

Having said that, the motor company says that 2HP and smaller motors are so short that they do not need a shroud to get adequate cooling. This should be taken with a grain of salt, as motor companies like to sell more motors. While this maybe somewhat true, especially when your old motor lasted so long, I still prefer to have a shroud or set the pump above the perfs to make sure the motor gets the most cooling flow possible.

Thanks Valveman for the reply!

As mentioned, I don't have the ability to set the pump above the casing perforations. Having said that, would you recommend the pump be raised OR just leave it where it is ............... 2 to 3 feet off the bottom? Your input is valued!

 

[Reach4]

So, I had a new well drilled just 15 feet away

Also 4 inch casing?

 

[Valveman]

The higher the pump is set in the well, the more flow will go past the motor. But the pump has to be lower than the lowest water level when the pump is producing max flow for extended periods of time. In wells where a shroud will not fit, I will check the pumping level of the well and set the pump a few feet below that.

 

[TVL]

Also 4 inch casing?

Yes, another 4" well just like the first!

 

[TVL]

The higher the pump is set in the well, the more flow will go past the motor. But the pump has to be lower than the lowest water level when the pump is producing max flow for extended periods of time. In wells where a shroud will not fit, I will check the pumping level of the well and set the pump a few feet below that.

As was mentioned in my original post, I monitor the static water level on a regular basis and during operation, the water level only drops approximately 2.5 feet. This means the static water level drops no lower than approximately 120' 3". The pump currently hangs at 142 feet.

As a note, this was mentioned in my original post: In the very BEGINNING, just after the well was first drilled, the static water level would drop approximately 13 feet while the irrigation system was functioning. This put the pump approximately 11 feet under water during operation and 24 feet while resting. I am assuming the well as further developed and for the past two years the water level only drops 2.5 feet as just mentioned.

 

[Reach4]

As was mentioned in my original post, I monitor the static water level on a regular basis and during operation, the water level only drops approximately 2.5 feet. This means the static water level drops no lower than approximately 120' 3". The pump currently hangs at 142 feet.

If you are concerned that having the pump set higher could cause the water to be pumped dry above the pump due to a change in something, there are devices that will monitor the pump current and shut down the pump for a while if that condition is detected.

 

[TVL]

If you are concerned that having the pump set higher could cause the water to be pumped dry above the pump due to a change in something, there are devices that will monitor the pump current and shut down the pump for a while if that condition is detected.

Thanks Reach!

No, I'm not overly concerned with pumping the well dry as the system has a control box with a PumpTec installed. However, I would still like to avoid pumping the well dry at all cost. Again, I'm simply looking for wisdom from the experts as to whether I can safely raise the pump possibly 6 feet, which would put the pump 9 feet off the bottom or at a depth of 136 feet, which seems to me the right thing to do. According to my monitoring data, the pump should not be able to pump the well dry unless I've missed something. I simply wasn't sure there may be other not so obvious items I should be concerned with by raising the pump that may catch me later down the road. Does that make sense?

 

[Reach4]

I am not one of the experts-- not even close. But it seems to me that your monitoring has given you very specific water level info.

On the other hand, remember that your previous pump did not fail due to the motor. The main reason, I think, that pumps are often set 10 or 20 ft above the bottom is to avoid sucking solids. Are you pumping much sand?

Is your pump cycling, or does it run pretty continuously during irrigation? If you are cycling, maybe your next pump should be smaller.

 

[TVL]

I am not one of the experts-- not even close. But it seems to me that your monitoring has given you very specific water level info.

On the other hand, remember that your previous pump did not fail due to the motor. The main reason, I think, that pumps are often set 10 or 20 ft above the bottom is to avoid sucking solids. Are you pumping much sand?

Is your pump cycling, or does it run pretty continuously during irrigation? If you are cycling, maybe your next pump should be smaller.

Thanks again Reach!

No cycling! I designed the irrigation system so that each zone would require the pump ran continuously. Naturally, some zones run at about 42 PSI, while other zones run higher at maybe 52 PSI. However, the pressure switch is set to cut on at 36 PSI and off at 58 PSI. I do monitor things regularly and the pump never shuts off during operation, which is exactly what I wanted!

I do pump a little sand. The system runs daily for approximately 6 hours and when I backwash the Vu-Flow screen filter it has what I estimate to be approximately 1/5 teaspoon of sand.

 

[Craigpump]

My feeling is....the well driller/pump installer you trusted to do the work knows the area better than the rest of us do, I for one wouldn't want to second guess his expertise in the local hydrology. He has the pump set at that depth for a reason and I think you should ask him if it's ok to set it a shallower depth.