1400ft off grid well

mayawk · May 2018

we had a well dug and ended up with 1.25 gpm at 1400ft deep, with the static level at 100ft. We will be entirely off grid and are looking at putting in a solar powered well pump. For the first year the solar pump will just be used for irrigation and construction uses, and will run on DC current into a stock tank. Once the house is built, the pump will be run off the solar power system for the whole house so it can run even when the sun is down. We are building a small house for 2 people, with modest garden and all composting toilets. The pump that has been recommended to us is the Grundfos 6 SQF 3, which has a max depth of 820ft and max pumping capability of 5.9 gpm. We would like to pump directly to a pressure tank once the house is built, which I have been told reduces the effective depth that the pump can handle by 140 ft. Hence, we are considering putting the pump in at about 600ft deep, which would give us about 750 gallons of storage in the well above the pump. A few questions:

1) one well pump installer has said that it is a bad idea to put a pump half way down a well, as the rest of the stagnant water below the pump is likely to grow bacteria due to the lack of circulation. Is this a real concern? Our well is drilled through solid granite bedrock with occasional layers of quartz.

2) is 5gpm adequate for normal household use?

3) is 750 gallons of water storage in the well with a 1.25 gallon recharge rate and 5gpm draw adequate for normal household use?

4) we know putting in a cistern would ensure we always have adequate water, but because the well is so deep, we are hoping to simply use the storage capacity in the well. Our concern is that the recommended pump might not be adequate because of the depth limit. Can that pump be placed lower? Would it decrease the flow rate? Is there another solar pump out there with a deeper capacity?

thanks in advance!

Estragon · May 2018

I'm way above my pay grade on this, but it seems to me the pump depth capacity would be above the water level, not the depth of the pump itself. It doesn't have to pump water to a level its already at, just from the top of that water column. Into a pressure tank increases the "head", or effective distance from the top of the water column. Whether the pump is near the water line, or much deeper shouldn't matter much in terms of delivering water IMHO. It might matter in terms of having anaerobic bacteria growing in a stagnant water column though. I don't know.

The well supplies at 1.25gpm, and the pump sucks out at 6gpm, so obviously the water level drops when the pump runs. The question then, it seems to me, is how far down does the water column get drawn, and can the pump handle it?

cow_rancher · May 2018

The well drillers at http://pumpsandtanks.com/ will tell you that the reason that the well was drilled to 1400 feet is that may be where the water was, even at 1.25 gal/min, the static water will rise to the static level due to hydrostatic pressure, it can even become an flowing artesian well and flow out the top of the well (we all should be so lucky), water in a well does not go stagnate, 4 Gal/min is the recognized flow rate for an FHA financed home, or at least it used to be, so yes a 5 GPM well is adequate. Using the storage capacity in the well is one way of dealing with a low flow well, I prefer using a cistern so I always know I have water, i.e. what happens if you leave the garden hose running all night? Pump will run dry, most likely with damage, so you may also want to consider a "Pumptec" type device to turn off the pump when it runs out of water, it is adjustable to wait until the well recharges before starting to pump again.
Hope this helps.
Rancher

mike95490 · May 2018

If your static level is 100', you can set your pump at 1400' and not worry about it going dry. When your pumping pulls the level down to 800' , flow will stop but the pump will continue to run and heat up without moving any cooling water.

Your 700' of 4" well pipe will hold about 450 gallons, and then you are limited by the recharge rate

I would vote YES for a ground level cistern, or a 50gal tank in the reinforced attic, to provide some water in case of trouble.

Type of Pump

Really only 2 choices

a) DC-Solar SQF style, several thousand for the pump, which might take a week to replace if it died, and cheap solar/battery to run it.

or

b) conventional 240VAC 3-wire pump down in the well, couple hundred bucks, stocked in every well supply shop, paired with a several thousand $ 240VAC inverter (which might take a week to replace) but any good size generator can run the pump in the meantime.

mayawk · May 2018

Thanks for all the helpful information!
Mike95490, are you saying that even though the well pump we're looking at says it maxes out at 820ft, we could possibly put it down lower anyway? Would that decrease the flow rate coming out to the house?

Just for some clarification, the SQF pump has an autostop mechanism in case of running dry, so it is not supposed to get damaged if it does run dry. The major water flow is coming in at about 1300 ft deep.

mike95490 · May 2018

The problem is you won't run it dry, it will be in water, but too deep to pump any, once your recharge rate slows down. So the pump will be running, but no water movement. It won't trigger any safetys, but after half hour, the water around the pump will be boiling hot.

Dave Angelini · May 2018

The test that the well guys often do not do is the time it takes before it is dry and at different times of year. It is the reason they want more flow to keep you happy. You will just have to test this.

You can also install a metal roof and capture rain for insurance.

Offgrid is all about being redundant in all of the basic requirements if you are going to live there full time.

mcgivor · May 2018

Surely placing the pump deeper than recommended depth would mean there is a possibility the draw down could result in exceeding the maximum head capacity of the pump, causing cavitation loss of cooling and premature failure. The attached pdf I found useful in understanding the basics, though my well depth is significantly less 140' static 18' refresh rate unknown but very generous. Dealing with such depths would require an accurate calculation, perhaps using an engineer/company who can gaurentee their installation would be prudent. Just a thought.

Dave Angelini · May 2018

mcgivor said:

Surely placing the pump deeper than recommended depth would mean there is a possibility the draw down could result in exceeding the maximum head capacity of the pump, causing cavitation loss of cooling and premature failure. The attached pdf I found useful in understanding the basics, though my well depth is significantly less 140' static 18' refresh rate unknown but very generous. Dealing with such depths would require an accurate calculation, perhaps using an engineer/company who can gaurentee their installation would be prudent. Just a thought.

That is a very funny statement you made. I am still laughing about well people guaranteeing anything 5 minutes after they leave. Add in the depth here and it really is funny!

For the OP here, an SQF will sense all the bad things listed and shut down long before any damage. You do have to have the electronics section working to sense flow. The Franklin and other old tech pumps can be protected also as mentioned.

mayawk · May 2018

Mcgivor, thank you very much for the PDF, that is extremely helpful! Now I have another question...

How do I determine what the pumping level (or drawdown) will be before putting the pump in? I'm assuming this requires a calculation of how many gpm is being pumped out, the volume of water in the well, and the flow rate, right? Anyone have a handy formula I could use?

FYI, I will use a professional well company, but so far the 3 companies I've spoken to have all given me different information and recommendations, so I'm trying to educate myself enough to understand the differences between what they are saying. So far, this forum has been most educational!!

BB. · May 2018

I am not a well guy, but I think the basic method of testing is they drop a large pump down the well and log water flow and water levels in the well as they vary the pumping rate (24 hours of testing or more?).

Bill

wellbuilt · May 2018

Bill is wright they pump the well .
In my area they test the water depth , then pump for 4 hrs and see how low the water drops.
Then see how long it takes to refill .
A easy test, my well is 800’ 3/4 gpm and I’m looking at the SQF pump.
My water level in September is 300’ down the rest of the year I have more water .
I plan on placing my pump @590’ @ 600 feet or more my well guy is suggesting I use galvanized steel pipe .
I will pump to a large tank with 5 solar panels and use a small pump to supply the house .

mcgivor · May 2018

How do I determine what the pumping level (or drawdown) will be before putting the pump in? I'm assuming this requires a calculation of how many gpm is being pumped out, the volume of water in the well, and the flow rate, right? Anyone have a handy formula I could use?

http://www.groundwatersoftware.com/calculator_7_time_drawdown.htm

The method I use as a safeguard is a float switch, which prevents running below a certain level, perhaps this would be a useful means in your case, always keeping a certain amount above the pump. The recharge of 1.25 gpm is not much, additionally that figure may change over the course of a year, unknowns are hard to plan for. The deeper the pump is placed the greater the energy required, as the static level drops being off grid this is an important consideration. Pumping for short periods like 10 minutes on 20 off for example would allows the well to refresh, so a smaller pump at a shallower depth could be employed..........just a couple of random thoughts

cow_rancher · May 2018

I am not a well expert, however I run a pumps and tanks forum that I kind of inherited because I didn't want to see it go away. I do own 2 wells, soon to be 4 wells, and in different parts of the country they do well "stuff" differently, here is AZ they don't bother to drop a pump down since they are using rotary rigs with high volume air to bring up the cuttings, they just stop drilling, leave the air on and measure how many seconds it takes to fill a 5 gallon bucket, all water in the well is bubbled to the surface, it's a fairly accurate method.

Rancher

mike95490 · May 2018

It's not the height from the pump, it's the height from the declining top of the water in the well casing. As you pump, the slowly recharging well will loose water, which is why the pump goes deeper then the static depth. Set the pump too shallow, and you will suck air quickly, too deep, and your power cable, even at 6ga, will have losses (and be expensive)

wellbuilt · May 2018

My driller did exactly what rancher said he blew the well and then waited an hour and blew it out again with the rig and estimated about 4 gallons minute based on volume of water that came out I couldn’t really tell the flow rate
But he does this every day .
The pump guys are separate here , usually they come with a pump truck with the boom and they have pumpsOn a big trailer to check the flow rate and all that or if the flow is very slow.
They bring in a hydraulic fracturing to Crack the rock ,
They also have pump Equipment because after Fracking the well, they pump it to open up the veins in the rock .
I have a lake house 800’ from a 32 mile long lake and my well was bone dry for 1100’ then I had a gusher , drilled to 1200 feet , I can see the water in the hole.
The pump is set at 300’ you never know but the water is sulfur

mcgivor · May 2018

@wellbuilt saidThe pump is set at 300’ you never know but the water is sulfur

Funny you should mention that, I used my well water for irrigation, some plants turned brown and died. Turns out the water is saline,, had to resort to pumping from rain water collection ponds consisting of 32 000 000 liters or 8 500 000 gallons, should have tested the water first I guess.

Dave Angelini · May 2018

It is about the water quality! If the OP lives in a place with decent rainfall, he should have a plan for harvesting it.

There are so many bad well stories I hear of with my clients and friends that stem from the drought out west.

The farmers are PO'd about the water going to the ocean and Socal and they drilling everywhere for irrigation in the valley that feeds the alot of country and even the world. It is sinking down there and these aquifers collapse and probably will never get their capacity back.

mayawk · May 2018

McGivor, thanks for the link to that equation. Unfortunately, i don't think I have all the numbers required for that, so I guess I'll just have to trust the well professionals on that point. I'm still unclear on how deep we can put a well pump that has a max head of 820ft if the static water level is 100 ft, the recharge is 1.25gpm, the boring is 6", and the pump extracts at 5 gpm.

Thanks to everyone for the recommendations on water harvesting. We will be doing some, but I live in Colorado, which means we're technically only allowed (2) 50 gallon drums to collect rain water in, and it's only permitted for irrigation. Silly, I know. But also, that's *technically speaking*... That said, we are also required to have a 2400 gallon fire cistern, which we're *technically* not supposed to ever touch, but we'll have that on the property, so if there's ever a time that the well pump isn't working, we will have access to some water.

Anybody know about issues with bacteria growing in the water below the level of the pump because of a lack of circulation? The well is drilled through solid granite with occasional quartz veins. Only one of the 3 pump specialists I've spoken to have brought that up as an issue, but it's pretty critical factor, as we'd be talking about the difference between putting the pump at about 600ft vs 1300ft. Those pipe and electrical costs add up quick!

cow_rancher · May 2018

mayawk said:
Anybody know about issues with bacteria growing in the water below the level of the pump because of a lack of circulation? The well is drilled through solid granite with occasional quartz veins. Only one of the 3 pump specialists I've spoken to have brought that up as an issue, but it's pretty critical factor, as we'd be talking about the difference between putting the pump at about 600ft vs 1300ft.

Bacteria needs to be there to breed, and your water could be coming up from the 1300ft level so I don't think you will have a problem, however you can have your water tested, and of course you can shock your well if you do discover bacteria. Like I said previously the driller may have drilled to 1300ft to hit any water, or he may have given up at more flow, that is something you have to ask the driller. I personally will be there when my next well is drilled, the last one was supposed to be drilled to 250', and he drilled to 120' where he said I had enuf water, as it turns out it was seasonal water and it will run low or completely out of water,... which is why I am drilling another well on this 15 acres.

Rancher

mayawk · May 2018

Hey Rancher, thanks for the thoughts. I was there while drilling. We hit 1/4 gpm at 300ft, and nothing more until 1300ft when we hit another 1 gpm. We went to 1400ft to ensure there would be no issue with sediment over the long haul. Not sure how we would test the water before selecting a pump...the static level is 100ft down.

wellbuilt · May 2018

My pump guy wants to put a 3 hp pump at 780’ with steal pipe and a wire the size of my thumb .
I think the SQF pump controler only works to 600 feet max .
Standard well pipe is rated at 300 for Polly and 500 ‘ +- for solid pvc sch 80 I think .
I would go 590’ and give it a try .
If you run out of water in the dry months you could allways add a storage tank and pump slow to match your Recovery
rate .

Dave Angelini · May 2018

My most recent deep well for a home was 3 years back. They used a

6 SQF-3 at over 800 feet. I was not there when it was placed in the well. This was in addition to rain catchment. As the OP said some states have weird rules. They are for city folks and rural offgrid homes are on their own. Just as we always are offgrid

I like that part!

There may be different models now that go deeper, I have not looked.

mayawk · May 2018

Hey Dave, do you have any idea how well the 6-SQF-3 functioned at 800ft? Where they able to get 4gmp?

Dave Angelini · May 2018

I can ask but I know it on a float switched 3K gallon tank. They may not know... To get that flow you do have to have enough solar to max the RPM. There is also the loss thru the 1" pipe at that depth and you will have to spend some time with Grundfos pump curves.
It also may not really matter if the pump can max rpm if the well draws down too fast....

I like the saying about all the ways well water bad and how very few ways that rainwater can

jonr · May 2018

> how deep we can put a well pump that has a max head of 820ft if the static water level is 100 ft

Grundfos (SQF) says a max of 500' below static level*, but I'd be conservative and put the 6-SQF-3 at 500' below the ground level. Don't worry about additional storage for normal household use (but irrigation would change things).

Be sure to use pipe that can handle ~250 psi (or set the pump even shallower than 500' below ground).

* - "Maximum: 150 m below the static water table (15 bar)". Page 35, http://net.grundfos.com/Appl/WebCAPS/Grundfosliterature-1569.pdf

Dave Angelini · May 2018

The previous post does not include all of the data that Grundfos lists

My experience is not from searching the web but actually doing the work of making it perform. Here is the curve I used.

1400ft off grid well

Comments

Categories