4 Year Old Well - Does This Mean Anything At All?

Discussion in 'Pumps and Tanks Well Forum & Blog. Water is life.' started by tvl, May 18, 2017.

  1. tvl

    tvl Member

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    Jul 5, 2006
    Location:
    South Carolina
    I had my second well drilled in the summer of 2013. The first well began yielding less water than was needed for the irrigation system. Even though the driller attempted to blow it out, he was not successful. It was believed the PVC screen sections had become partially clogged with sand over its 35 year life.

    The new well was drilled only 35 feet away and is at the same exact depth as the original. It has and continues to yield the watering requirements for the irrigation system. I closely monitor the draw down and it is the same now as the day it was drilled.

    The new well is 151 feet deep
    The static water level is 111 feet
    The pump hangs 135 feet from the top of the well casing
    Drawdown of water level is approximately 2 feet during operation

    I started irrigating in late March of this year. The system runs daily unless we have had adequate rain, at which time it automatically shuts off until the sensor allows the system to run once again.

    About 3 weeks back, I noticed the sprinklers were not running one morning. After close examination, I found that the 100 mesh screen on the filter was caked with what appeared to be a very thin layer of clay. (Note: this is a sand well, but they did go through a layer of clay when the well was being drilled). I cleaned the filter and all has been OK up until today. Today, the filter was once again caked with a very thin layer of what appears to be clay. Does this mean anything?

    I do recall this happening once last year. This well and the initial well have always had a small amount of very fine sand mixed with the water. This is why I utilize a filter ............. to keep sand from getting into the irrigation sprinkler heads and valves. I check the filter at least 3 times a week. If I were asked how much sand is being pumped DAILY, I would guess about 1 tablespoon. And that is after pumping continuously for 6 hours and pumping approximately 3,600 gallons of water.

    However, the clay coating on the filter twice this year, which essentially plugs the 100 mesh screen, has me concerned. Or is this a concern at all?

    Thanks for helping!
     
    Last edited: May 20, 2017
  2. valveman

    valveman Cary Austin Staff Member

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    Is this problem associated with a rain event? If not you might just need to pump the well out at full pump flow for a while to see if you can get it developed and not making sand and clay.
     
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  4. tvl

    tvl Member

    Joined:
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    Thanks Valveman!

    1- No, this was not associated with a rain event.

    2- As mentioned in my original post, this well and the original well pumped a little sand. So, I'm thinking that must be normal for these parts. Two different drillers were used for each well. Anyway, the 100 mesh filter keeps all sand from the irrigation system. (I estimate 1 tablespoon per 3600 gallons of water pumped each day)

    3- I'm just not sure what to make of the 2 instances of the filter being plugged with a thin layer of what appears to be clay. And the instances occurred about 3 weeks apart, not in 2 consecutive days. Again, maybe it means nothing, but hopefully, someone can explain what creates this issue.

    Thanks!
     
    Last edited: May 22, 2017
  5. valveman

    valveman Cary Austin Staff Member

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    Sometimes a well will make stuff like that when the pumping level drops. But again is sounds like the well needs to be developed.
     
  6. tvl

    tvl Member

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    Thanks again Valveman!

    OK, I have one other question. You stated: "sounds like the well needs to be developed"

    After pumping well over a million gallons of water in almost 4 years, shouldn't the well be developed by now??

    PS: Per someone's recommendation on this site several years back, the well has a 1/4" tubing placed down along with the pump & drop pipe with a pressure gauge attached up top so that I can monitor water level by viewing the pressure fluctuations. During the watering season I check this gauge DAILY. The water level on our existing 4 year old well has never dropped more than 3 feet during a watering session. (which was approximately a 1.25 psi drop on the pressure gauge - most days it isn't quite a 1 PSI drop - so this well has never had to struggle to keep up with the demand)
     
    Last edited: May 19, 2017
  7. valveman

    valveman Cary Austin Staff Member

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    Developing the well means pumping a higher volume than would normally be used. A wide open pipe with no sprinklers or anything for a restriction will let out more GPM than when running pressure for the sprinklers. Higher volume of water will draw in more sand and clay and help clean the well. It is also possible that you would need an even larger pump to do this since it doesn't look like the pump you have is making a dent in the production of the well.
     
  8. tvl

    tvl Member

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    Well, it looks as if I may need to look into getting this done at some point.

    Last thought: Are you also implying that even though a well gets used a LOT, such as mine has, this still won't develop the well over a course of time? I would have thought that by pumping thousands & thousands of gallons of water over time would have been the same as pumping out one huge amount over the course of 24 hours. But then, I'm no expert and that is why I'm asking!
     
  9. VAWellDriller

    VAWellDriller Active Member

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    That's exactly right on a good producing screened well...This is a problem I have on high yielding wells that end up with a small pump in them. Your well could make the 15 gpm you are pumping all in 1' of open 4" well screen. I don't know how much screen is in your well, but its very possible for lots of residual drilling mud to be left in screen and stay there for years.
     
  10. tvl

    tvl Member

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    Just in case you were curious .................. there are two 20 foot sections of screened PVC at the bottom of the well.
     
    Last edited: May 20, 2017
  11. VAWellDriller

    VAWellDriller Active Member

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    Sometimes if drillers arern't sure about formation, they put in extra screen to make sure they get some in the right spot. Thats a lot of screen though, and much or most of it is unproductive based on your water level. It probably still has lots of drilling mud in it. But, it seems you have a very good well and it's not causing any major problems. I wouldn't worry about it.
     
  12. tvl

    tvl Member

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    Thanks VaWellDriller!

    I was there when the well was drilled. I remember when they indicated they had hit water. From that point to the bottom of the sand aquifer was approximately 40 feet. So, I'm assuming this is why 40 feet of screen was installed.

    Out of curiosity you stated: "Thats a lot of screen though, and much or most of it is unproductive based on your water level". If the well is 151 feet deep and the static water level is 111 feet, that equals a column of water 40 feet in depth. Doesn't that indicate that all of the screen is productive? Or, is my thinking incorrect?
     
  13. VAWellDriller

    VAWellDriller Active Member

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    well....a couple posts up you said it had 80' of screen...so thats when I made that comment. Just because all of the screen is wet, doesn't mean it's all producing. Your well is in a sand layer in the Atlantic Coastal Plain, not sure which aquifer.....these aquifers are almost always artesian (meaning that the water is under pressure and when relieved by a well the water rises above the aquifer---rises in the well higher than the screened interval).....close to the coast, the some of the aquifers may be very deep (like 800' wells with 10' of screen that have a static water level of 20' or less and make hundreds of gpms with little or no drawdown).....towards the west as the geology starts to turn to piedmont, they may be like yours....just a saturated layer of sand that is not under artesian pressure. In your screen length, whether 40 or 80'; you could easily be getting most of the inflow into the well though a few feet of screen; and the water is just rising higher in the rest. I suspect you pump sand because the pump is set inside the well screen......generally a practice we try to avoid when it is possible.
     
  14. tvl

    tvl Member

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    Thanks VaWellDriller!

    Yep, that was a typo regarding two 40 sections. I've edited that post to indicate there are two 20 foot sections of screened PVC. Sorry about the confusion!!!!

    And yes, of the 40 foot of screened PVC, the pump is hanging about midway in this length of pipe.

    My first well had practically the exact same setup. This new well basically mirrors what I had originally. I guess that is why the well driller did what he did. The original well did last 35 years before it began to have less volume. Everyone still speculates the screen in that well most likely became clogged with sand over the years making it difficult for water to get through. The original well also had 40 of screened PVC pipe in it.
     
  15. VAWellDriller

    VAWellDriller Active Member

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    I suspect they are right about your old well....or it wasn't ever quite as good a well as the new one. Mud rotary drilling and setting, gravel packing, and developing a screened well is as much an art as it is a science. 3 well drillers could drill the same hole in the same spot, and install the same well screen and all get a different amount of water. It's hard to explain that to customers, but it is reality; sounds like you got a good well this time. If he did it right, picked the right size screen and gravel pack, the yield will not drop off over time.
     
  16. tvl

    tvl Member

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    Well, I'm not complaining about the first well. For 35 years it gave a LOT of water ............... and I mean a LOT! I figure well over 30 million gallons in that 35 year period ................ and that is probably being a little conservative.

    Of course, it pumped sand also. I didn't have a filter on it until near the end of its life. So, I can't really say one pumps more sand than the other or not. Anyway, if the new one last 35 years, it will likely outlast me!

    Even though it's a small amount of sand (approximately 1 tablespoon per 3600 gallons of water pumped), I still wish I could eliminate it altogether. However, with a 4 inch well, I'm hearing there isn't much to do now.
     
  17. tvl

    tvl Member

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    ***** UPDATE ***** UPDATE ***** UPDATE *****

    I awoke this morning to get ready for church and noticed the sprinkler system had not run in the back yard. After returning from church, I discovered the filter was once again caked with “mud” and plugged. This is the 4th time this has occurred this year or since I began watering in late March.

    In an earlier post, Valveman had indicated my well might need further development to help clear up any sand or mud. Well, I’m certainly no expert at how to do something, but I tried my best to do just that with what little knowledge I possessed. I disconnected the piping at the well head and let the pump run full force with no back pressure. I measured the output at the beginning and the end of the adventure: the pump was outputting 14.25 gallons per minute the entire run. I allowed it to run 2 hours and 40 minutes. Interestingly, the water was clear as a bell from the beginning to the end.

    The gauge for measuring the depth of water above the pump was reading 11.0 PSI (25.4 feet) before start up and 9.8 PSI (22.6 feet) during the ENTIRE run. That is only a 2.8 foot drop in the static water level, which is almost exactly what I normally see on a daily basis when the irrigation system is running. The irrigation zones are setup so that each zone uses approximately 11 to 12 gallons per minute. So, with the pump running with no back pressure, I was only outputting and additional 2 gallons per minute. I’m assuming this isn’t enough volume to clear up the well. Is that a correct assumption?

    But again, why was the water so very clear during the entire “purge”. If there is driller’s mud or clay down there, one would have thought the water would have shown at least a little discoloration at some point??? But, it never did ................ just clean crystal clear water!


    Edit (after thought): by connecting the piping and sprinkler system, this obviously adds back pressure to the pump. Is this back pressure what's helping to cause things to get stirred up in the well? and if so, how?
     
    Last edited: May 21, 2017
  18. valveman

    valveman Cary Austin Staff Member

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    Back pressure does not stir up a well. Back pressure just makes the pump produce less flow. Like VA says 14 GPM could be coming from 6" of that screen. You would need to pump a lot more water to develop the rest of the screen. A surge block pulled up and down the well or air blowing with a big compressor could shift things around and let the gravel pack settle in and filter everything better. But it is possible to spend more developing a well than drilling the well. So if it only makes a teaspoon or two occasionally, you might can live with that. When a well makes a wheel barrow full of sand every month or so you have a real problem and spending some money to fix it it well worth the expense.
     
  19. tvl

    tvl Member

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    I happened to come across something today that I would like to see if any of the experts here would recommend or comment on:

    From my information above, all can see that the Vu Flow filter I have installed for the irrigation system accumulates about 1 tablespoon of very fine sand each day. If I'm to go on an extended vacation, I don't like to leave the system on because I'm afraid the sand will build up and plug the filter. However, it appears there are purge valves that can be attached to the filter for purging on a daily basis. This sounds perfect!

    http://www.discountfilterstore.com/afv-rusco-automatic-flush-valve.html

    1- Anyone care to comment on this type device?
    2- Do the valves normally perform flawlessly .......... or will it possibly create other issues?
    3- Are you aware of cheaper versions that will do as good of a job?

    Once again, thanks for your help!
     
    Last edited: May 22, 2017
  20. VAWellDriller

    VAWellDriller Active Member

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    Occupation:
    Mud rotary well driller, pump installer
    Location:
    Richmond, VA
    Lakos makes an auto purge valve that I have used a couple times with no problems at all.
     
  21. tvl

    tvl Member

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    Jul 5, 2006
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    Thanks so very much for the response VAWellDriller!

    Would you happen to be referring to this particular unit? It would be used for a 4" residential well with 1" water piping attached.
    https://cannonwater.com/lakos-residential-auto-purge-valve-for-sandmaster-135259/

    Edit: I came across this unit after further research. I'd really hate to spend this amount of money, but it appears there aren't too many models available:
    https://www.freshwatersystems.com/p...61496A297CB5&gclid=CLys-5HLhtQCFY-2wAodB9gH0g

    Also, after going to the Lakos website, I saw they also offered centrifugal-action sand separators. The units I'm speaking of were for above ground installation, appeared they might very well do the job with no moving parts or power required, BUT were very pricey (about $900 for my setup). This type unit is actually overkill for my needs, but do you have any comments regarding this type unit versus the filter mounted purge valve? If the purge valve unit would do as good a job, that seems to be the best way to go. I guess I'm concerned the purge valve, with moving parts & power glitches involved, might be more trouble than they're worth??

    Thanks!
     
    Last edited: May 23, 2017
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