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Gallons Per Minute for Well

jrh's picture

I'm having a drilled well installed on a site south of Atlanta.   After going down 650 feet, the well drilling company tells me the 2 gallons per minute rate is adequate for my 4 bedroom house needs.  He says the 6" well will hold roughly 900 gallons which I understand; however, my concern is at only 2 GPM, will I still have water when the drier weather begins.  Do well drilling companies generally warrant a well for at least a couple of years?

(post #69708, reply #1 of 53)

Hey j ,


  I'm not sure what you are asking them to warrant ? They might warrant their workmanship or the pump and materials . But they can't warrant water flow . How would you even be able to check out what they tell you if you have a problem . Two gallons a minute is two gallons a minute!  Well drillers are an odd buch of guys, in a good way .


 


DAVE

(post #69708, reply #2 of 53)

How many gpm are you planning to pump?  Not difficult to calculate when you'll pump it dry with a sufficiently large pump.


We have a tiny reservoir compared to yours, also 2gpm when I drilled, never have pumped it dry.  We could, but don't.  Irrigating the garden is no problem and we don't restrict our indoor use.  Measure your shower flow sometime.  "Drier weather" isn't a well problem unless you get into a several yr drought. 


Well drilling is always a gamble, that's why I bought my own rig.


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(post #69708, reply #3 of 53)

Bump.


I am not a "well savy" person but I would like to know the answer, edumacate me too!


650' of 6" bore hole will hold ~950 gallons of water if it is actually full.  This 950 gallon reservoir would provide ample water and be replenished at the rate of 2 GPM.  Note: at 2 GPM it will take 7.9 hours to fill / refill the bore.


My question is how does the bore get full?  If you had to bore 650' down - what makes the water rise to fill the bore?  Seems to me the well driller would only bore as deep as necessary and I don't think the water table is pressurized to make it rise in the bore - was there water running out of the bore hole when he finished drilling?


I've been wrong lots of times before.


Jim


Never underestimate the value of a sharp pencil or good light. 

Never underestimate the value of a sharp pencil or good light.

(post #69708, reply #4 of 53)

I hit water at 90', under a layer of quartz.  Rose to 40' from the surface.  This is on top of a mountain even.  There's pressure down there.  During drilling it's also common to hit several small flows on the way down, none adequate by itself.  Didn't happen for me, but it's common.

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(post #69708, reply #5 of 53)

at 650 feet 2 gallon per minute is pretty good. mine is only 60 feet and i get just a hair over 5 gallon per minute. I think its more the pump itself than how much it will flow.

. 2+3=7

(post #69708, reply #6 of 53)

        You can't get Water there with out a pump. With that much head you would need a submerged pump at the water level to pump to 650'. In the south you drill until you hit sand (clean potable water). This sand comes to the surface with the water used to drill the well. In Mobile we only need to drill to about 60', maybe this is different in other areas (material to drill through). I use a pump above ground with a 60' suction pipe. As far as I know there is no practical way to increase the volume or pressure with out using a submerged pump at a depth of 650'.


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(post #69708, reply #7 of 53)

We recently drilled a well that draws about 2 GPM.  The well driller advised us to put in a holding tank (I think it is 1500 gallons) that the well pumps into, then pump out of that resevoir to keep pressure constant at the house. 


This was far cheaper than drilling the expected 150 extra feet, and there are a few dry holes in the area, so we took his advice and haven't had any trouble yet. 


Might be a solution that you could use, might not.  Just thought I'd mention it.  


 


 

(post #69708, reply #9 of 53)

What Jim describes is very common out here.  My system pumps about 2.5 to 3 GPM from 350 feet.  We have about 7500 gal of unpressurized storage.  This serves 4 households.  Usage tends to be peakish but a dozen hours of well pumping restores the storage system overnight.  The only problem comes if someone leaves a faucet on or a pipe breaks.  The storage is also useful to tide us over if the well needs repair.


Erich

(post #69708, reply #10 of 53)

Thanks for the input,  my original question really is, do well drillers guarantee their work for a warranty period.?   For example,  if the well dries up after 1 year,  do they normally come back and drill another or deepen the existing well without any extra cost to the homeower?   Based on your responses I think pumping with a submersible pump from 650' down and given the  storage capacity of the bore hole will give me plenty of reserve unless as you say, someone leaves a faucet on.  I can add reserve storage later if needed. 

(post #69708, reply #11 of 53)

No, they don't gaurantee it to produce water anymore than the weatherman gaurantees whether it will rain, snow, blow, or shine.

 

 


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(post #69708, reply #12 of 53)

why would they, all they are doing is supplying the labor. The bore of the hole has nothing to do with storage. Its not storage till it gets above ground.

. 2+3=7

(post #69708, reply #8 of 53)

Mine produces between 3 and 3.5 GPM. nEVER A PROBLEM FOR HOUSEHOLD NEEDS, BUT OCCASIONALLY IN THE SUMMER, IF SOMEBODY FORGETS AND LEAVES THE SPRINKLER ON ALL NIGHT, THE water takes on mineral colour cause no time to settle out

 

 


Welcome to the
Taunton University of
Knowledge FHB Campus at Breaktime.
 where ...
Excellence is its own reward!

 

 

Oh Well,

We did the best we could...

(post #69708, reply #13 of 53)

I'm no expert, but here's a few basics:

The water level where it stands in the well is called the "static level", at least in the rockies where I'm familiar. The static level actually goes up and down seasonally in most wells around here.

Two gallons a minute is equal to 2,880 gallons a day, IIRC. Since most households use 5-10k per month you should have plenty of water. As others have alluded, the trick is to have the amount of water you need, when you need it.

I agree with blodgett's well man: put in a cistern.

A tank in the ground (cool drinking water in hot weather), usually either precast concrete (my preference) or plastic (has to stay full of water or lateral pressure from the ground around it will tend to collapse it bit by bit if you run it low... and the point of the tank is to be able to run it low!) is best.

The cistern also has another benefit. The wear on the submersible pump is primarily from starting up. If the well is deep it takes a lot of power (both starting horsepower and the electricity to run it) to get going. If the pump is also pressuring the system there is just that much more work for the pump to do. If the pump pumps directly into a non-pressured holding tank it's easier on the pump. It is also better to run the well pump with a float switch than a pressure switch since the float can be set so as to pump more water at one start up. i.e. if you have a 60 gallon bladder type pressure tank with a pressure switch to start the well pump, you will never pump very many
gallons of water per start-up of the well pump. If you have a three thousand gallon holding tank with a float switch set to turn on the well pump, you can safely pump out 80% or more of the holding capacity of the well itself (say the well shaft holds 400 gallons between the static level and the bottom of the pump. You could probably pump 300 gallons or more at one pump start-up). If you start the pump so many fewer times it will SAVE YOU BIG BUCKS in the long run. Ask your pump man how much it will cost when you finally burn up the well pump and call him to come out and replace it!

You obviously also don't want to run the pump dry and you don't want it too close to the bottom since it will be more likely to pull in sedement.

If you have a pressure pump that does nothing but pressurize the system that pump is cheap, easy to repair or replace, and, especially!, easy to get to.

With this type system you will also have enough water on hand to run your household for quite awhile if you are waiting for the well man (or woman!) to show up and replace the pump. You will also have a standing amount if a drought slows your well recovery rate (the 2 gpm you mentioned).

You can also put the well pump on a time switch that only allows the pump to start every few hours. That assures that the well has recovered before you pump again.

All this may sound elaborate, but the long term savings, the ability to pump a thousand gallons or more at once if you need it for watering, car washing or a fire, the protection from drought (and the ready to use system for handling water should you ever have to have it trucked in temporarily) all make this type system superior, IMO. As Mike would say: whudda I know.

Around here we have all sorts of well problems: Low flows (There's someone here who lives on a one pint per minute well), sulfur, iron, and drought. It's not unheard of for a driller to hit an un-mapped mine hole in certain areas and in the solid rock they are sometimes drilling in around here they will occasionally hit water, test the flow, set up the system and then find out later that it was a captive pocket that runs dry never to refill again.

Happy new year and best of luck with your well.

Life and suffering are inseparable.   


"Doubt is not a pleasant condition, but certainty is absurd."

~ Voltaire

(post #69708, reply #15 of 53)

All this may sound elaborate, but the long term savings, the ability to pump a thousand gallons or more at once if you need it for watering, car washing or a fire, the protection from drought (and the ready to use system for handling water should you ever have to have it trucked in temporarily) all make this type system superior, IMO


I'd agree with most of the above.  Clearly not the "long term savings".  Considered setting up such a system, priced it, and concluded the payback was... never.  We're submersible and pressure tank only.  Due to our odd system (large pressure drop) and poor advice from the pros, run it 80/100 psi.  Works fine although I was sold 2 wrong pumps before the factory finally told me which was correct.


My pump's been down there for 15 yrs, no service required.  I do keep a spare on the shelf 'cause it'll probably be a holiday weekend when it finally quits.  Replacing a pump isn't particularly difficult.  Pretty sure I'll still remember how, when I finally have to.


I was amazed when our health dept. approved a 3 br house on a pint/min well here.  Small property with 4 previous dry holes.  I was a little surprised anybody bought it.  To get a building permit here you now have to prove water.     


 


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(post #69708, reply #17 of 53)

Replacing the pump your self depends on a variety of things. You and I could do it perhaps, but even that depends on how it was done to begin with. If it's on steel pipe it'll take a rig. I know you have one, but virtually no one else does.

I've seen plenty of pump failures. Good for you that you haven't had one.

Life and suffering are inseparable.   


"Doubt is not a pleasant condition, but certainty is absurd."

~ Voltaire

(post #69708, reply #27 of 53)

If it's on steel pipe it'll take a rig.


LOL  That would change the economics.  A buddy had one like that, went out on Easter Sunday a few yrs ago.  Couldn't even get a driller to return his calls, much less come out.  2 commercial greenhouses were at stake.  He wasn't asking how much, just when.


I called another friend.  3 of us, an extension ladder, lever handle chain hoist, and an improvised clamp did the job.  We hauled out ~350' of pipe.  Replaced by plastic of course.  Took an hr and a half to set the ladder and get the pipe out of the well.  Lots of cranking on the chain hoist.


Next time it goes he knows to put a tire rim next to the well head, attach his truck to the pipe/rope, and drive slowly off until his spotter sees the pump.  10 minutes tops.


My rig uses such short stems that it wouldn't be significantly faster than the chain hoist.


I'm pretty sold on Grundfos pumps. 


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(post #69708, reply #28 of 53)

I lived on an island in Puget Sound from 89 to 94. I could never understand why, but they were still installing new steel pipe. Even 120 feet of 20' sections were way beyond almost any homeowner.

Life and suffering are inseparable.   


"Doubt is not a pleasant condition, but certainty is absurd."

~ Voltaire

(post #69708, reply #30 of 53)

Even 120 feet of 20' sections were way beyond almost any homeowner.


Way beyond me too, without some mechanical advantage.  But then I think every homeowner ought to have a decent comealong.  And everybody at least knows somebody who owns an extension ladder.  Makes a pretty good A frame.  Clamping the pipe (to reposition the 5' chain hoist) on the way out was the trickiest part. 


I could never understand why, but they were still installing new steel pipe.


Beats me.  I was shocked when I recently learned that they still sell steel well casing here.  No idea who uses it.


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(post #69708, reply #33 of 53)

VaTom - what are you casing wells with down there?  I had a pvc casing crack on me once, (months of mud, filters & fun) and I was planning on steel this go round.


Is there a better option?


 


Treat every person you meet like you will know them the rest of your life - you just might!
Treat every person you meet like you will know them the rest of your life - you just might!

(post #69708, reply #36 of 53)

Seems you're one up on me. 


I've never seen a problem with pvc, which I had previously assumed everybody here used.  Maybe drillers here use steel when they have a customer with your experience.  Don't know.  Somebody's buying the steel here.  The supplier didn't have an answer when I asked who.  They guessed around 5-10% of the casing sold.


You're right about one thing though.  The casing only has one job to do.  If it fails, the well's pretty worthless.  Was there a repair or were you stuck with another bore?


I guess, now that I think about it, chances are good that I could pull my casing and replace it.  That's if the bentonite surrounding it would let loose or succumb to being washed out.  PITA though.  My rig, unlike large commercial ones, has a separate engined high pressure water pump on it.  Meant for drilling without a hammer and compressor.  Useless around here.


Far as I know, steel rusts.  We typically have acidic water and while the casing isn't normally in contact with the well water, our ground water is likely acidic also.  Doesn't sound like a great combination.  I'll stick with pvc.  2 more wells and my rig goes to a new home.  Not a business I enjoyed.  Hitting a good flow is pretty exciting, but the rest isn't anything I want to spend much time with.


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(post #69708, reply #44 of 53)

Va Tom - Our cracked casing didn't cause trouble until the drought hit a few years ago - it stops raining, and we get mud - huh?


Anyway we put in a smaller casing with a "packer" basically a gasket - to seal inside the pvc.


If pvc is usually fine, I'll probably stick with it for the next well - steel costs more anyway.  My bad experience was probably rare - although I believe the drillers use the rig to push the pvc down - great potential for overdoing it.


 


Treat every person you meet like you will know them the rest of your life - you just might!
Treat every person you meet like you will know them the rest of your life - you just might!

(post #69708, reply #47 of 53)

If pvc is usually fine, I'll probably stick with it for the next well - steel costs more anyway.  My bad experience was probably rare - although I believe the drillers use the rig to push the pvc down - great potential for overdoing it.


Well, I notice that there are several posts where health depts. require steel casing, just not here.  Not that our health dept. is lax, far from it.  They don't approve anything new until it's been in service elsewhere for several yrs, like the Infiltrator septic systems.  I never asked them about steel casing.  Don't know what drillers with large rigs do for casing installation.  My rig won't push very hard, nor have I had, or heard about, a (pvc) casing problem here at all.  Grout is another matter.


CYA, profit margin, or convention might be what the drillers are doing there.  Or they may know that pvc doesn't work well there, shifting geology or whatever.  I don't know.  How a drought could crack a pvc casing I don't understand at all.  Now, if your casing wasn't sealed well enough and some surface water, or dirt, got down there around the bottom of the casing, you'd have mud for sure.  Or if the joints weren't glued well and grout failure.  Or it was cracked on installation and your grout failed at the crack...  Do they use bentonite grout there?  I'm a true believer.


When I called to ask about steel casing here, the driller supplier wanted to know what I was doing with it.  Seems some have tried to use it for culverts.  Doesn't hold up to vehicle traffic.  I drive over buried pvc everytime I go up or down my driveway, protects my driveway sensor.  Same schedule as the well casing, no problem with my not-exactly-light-weight traffic.


No recommendation.


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(post #69708, reply #49 of 53)

"CYA, profit margin, or convention might be what the drillers are doing there.  Or they may know that pvc doesn't work well there, shifting geology or whatever.  I don't know.  How a drought could crack a pvc casing I don't understand at all.  Now, if your casing wasn't sealed well enough and some surface water, or dirt, got down there around the bottom of the casing, you'd have mud for sure.  Or if the joints weren't glued well and grout failure.  Or it was cracked on installation and your grout failed at the crack...  Do they use bentonite grout there?  I'm a true believer."


I think it cracked at installation, then the drought freed things up somehow - clear water for 3 years then mud.  Cement grout - 11 bags - but something wasn't done correctly...  I'll be there to watch this time.


Our geology is limestone karst - basically swiss cheese rocks - but I believe we were drinking surface water mud - with all the cows within 1/2 mile, I'm certain it was healthy for us, too.


 


Treat every person you meet like you will know them the rest of your life - you just might!
Treat every person you meet like you will know them the rest of your life - you just might!

(post #69708, reply #35 of 53)

Vermont requires steel casing, a minimum of 20' even in a bedrock well.  Gravel wells must be cased all the way.  Most of the New England states (may be all) require steel casing for a potable water well.

 

 

(post #69708, reply #37 of 53)

Pretty sure that has to do with what you're drilling through.  Glacial till? 


Here, we generally have decomposed stone down to bedrock, soft to where the casing ends at bedrock.  Health dept. told me to case down to bedrock.  Great! That's about 6" on top of this mountain.  "Nooooo, minimum 20'."  I got down 32' with my soil bit before it wouldn't go any further.  Case, and switch to the hammer for the rest of the trip.  15 yrs later my pvc casing is doing what it's supposed to do. 


The other side of the Blue Ridge Mtns, casing can extend hundreds of feet due to the geology.  I'm gratefully ignorant of what they go through.  Wells typically at least twice our cost.


When I had a real estate license here the only steel cased wells I saw were old ones, often with rust problems. 


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(post #69708, reply #48 of 53)

JonE, where you located in Vt? Just drilled my well this past year and installed my septic for a vacation home I'm building in Vt, and you are correct about the steel casing. Lots of water up there too.

(post #69708, reply #50 of 53)

Southwestern corner.  Just north of Bennington.

 

 

(post #69708, reply #41 of 53)

Steel well casing is still required for the first 60 feet of any new well in Colorado.

Life and suffering are inseparable.   


"Doubt is not a pleasant condition, but certainty is absurd."

~ Voltaire

(post #69708, reply #31 of 53)

I'm amazed that 3 gal/Min sounds decent to all of you. I'm a Real Estate Broker in Western Oregon (lots of water its true) but lenders don't like to finance a home unless the well gets 5 gal/Min or more. I think a storage tank is called for at 3. for sure.


We are going to build new this year, does anybody know how close to the home a well needs to be? I assume that additional pumps could send it uphill several hundred feet if necessary?

(post #69708, reply #38 of 53)

We are going to build new this year, does anybody know how close to the home a well needs to be? I assume that additional pumps could send it uphill several hundred feet if necessary?


That I have a little experience with.  I wanted to drill 700' and ~150' elevation down from the house.  Tank and switch in an outbuilding near the well.  The driller supplier did a bunch of calculating and said "no problem".  Wrong.  We got a 50 psi pressure drop.  Standard switch only adjusted up to 60/80 psi.  Shower?  What shower?  Great result for a first experience...  No, they wouldn't take the hardware back.


Got with the pump mfg. and pressure tank mfg. to get the right answer.  Took each of them less than a minute to tell me what I already knew, that my hardware wouldn't work.  Took a different pump before I finally had the right one.  Not hp differences, some are designed for high heads.  Lifting the water, rather than friction from the long pipe, is the main thing.


We run our pump 80/100 to get 30/50 psi at the house.  Works fine, but reduces the effective size of our pressure tank.  Clearly, the pump doesn't mind the push.   You learn to be cautious opening the hydrant at the outbuilding.


Better, and perfectly workable, would have been to place the switch and tank in the house, rather than the outbuilding near the well.  But by the time I knew I had a problem the trench had been filled and I didn't want to re-dig it.


The drillers (that I didn't hire) at least gave me the right answer (for them) to whether it'd work: "I don't know."


Did I cover your situation are are you lifting water a lot higher/farther?  Talk to the pump mfg.  They'll get you straightened out.  Probably not much of a problem.  Don't forget to put check valves in the line on the way up.  I used 2.


 


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