Geothermal heat pump that dumps back into well

Discussion in 'Open Loop' started by GEM, May 8, 2012.

  1. Calladrilling

    Calladrilling Member Industry Professional Forum Leader

    In NJ your return well needs to dump back into the same aquifer as the supply well.
    A return well can usually accept as much water as it supplies if dug to the same aquifer and has a good screen on it.
  2. Rig 40

    Rig 40 New Member

    Idaho, washington and oregon all require injection into same aquifer as well. Pretty common practice. Depending on gravel sizes and volume to be pumped you may not need a screen but I would be leary of a driller that just wants to drill a hole with no idea of how to "calculate depth" for the injection well. General rule here as is most places is that a well will take as good as it gives. A screen just makes the well a bit more bullet proof on both ends.
  3. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader


    I'm going to stress a bunch of caution here. I'm not a hydrogeologist but I took enough of it at University and worked enough with the guys in a previous life to know injection is not the same as extraction. If somebody told me to make a 5 second decision, I would say "twice the screen."

    Get somebody involved that can figure it out for you. "Calculators" on the ground:).
  4. Palace GeoThermal

    Palace GeoThermal Well-Known Member Industry Professional Forum Leader

    I second Chris' words of caution. I have seen re injection wells that quit taking water not long after being put in service.

    It is not a simple as drilling a well and dumping water in.
  5. Calladrilling

    Calladrilling Member Industry Professional Forum Leader

    The only time I've seen in return wells not work as well as supply wells is when your in aquifer that does not supply a lot of water to begin with, the water is high in iron, iron Bactria, or some other minerals that can cause scaling inside the return well and clog the screen. That is why I said a good quality screen be used. I standard 4"x 10' 15 slot screen should be able to handle a supply of about 75 gpm easily in a good aquifer, and also except the same amount. The min issue with return wells is all about water quality, and screen placement/packing.
    I do not know your area, or water quality but it's all things the driller should be able to help you with. He should have knowledge of all this.
    Your driller should also know how deep to drill your supply well too. ( maybe you should talk to another driller for reassurance).
  6. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    " maybe you should talk to another driller for asurance":)

    A real pearl of wisdom!!!

    This is the gist of this entire thread. Proffesionals disscusing abstracts and things we do in our OA. I and others urge you to only use the info here for education and hire a pro in your locale to put the tool to the ground for your project.

  7. Kogashuko

    Kogashuko Member

    Warning if you arnt interested in my rambling skip to the last paragraph. I like to give the history of my thought process and think I could be considering the same setup as you with a solution. I am also new to the geothermal community and have considered a lot of stuff people already have solutions for.

    /--------------------------- Start of my rambling ---------------------------------------/

    Did you ever sort this problem out? The only reason I ask is because I am considering a geothemal unit on my addition. I have considered a lot of things including replacing one or two of my newer air source heat pumps if the load is too high for them with the extra space. However, the efficiency of smaller geothermal units make me one to go with two separate heat pumps at least. Meaning I could eventually have 2 or 3 ground source heat pumps. From what I have read this gets really complicated with a closed loop.

    I found this thread because open loop seems to be the most efficient as long as you get the right coil and maintain the system right.

    My problem might be similar to the one you have which is why the water is injected back into the same well. I have a shallow well which is an old stile 3 foot wide well that hits water at about 35 feet. If I were to pump and dump I would surely run out of water and probably exceed the maximum recharge rate. Most of the people on my block have had to have new deeper wells dug. However, I think it was possible they were scammed. First, all of the wells originally had non-submersible pumps and the pump was simply powered on a pex type tube about halfway down to overcome the 25 foot pumping distance. The hose ended up not being very deep into the water. Second, most of the pressure tanks in the homes were too small. This means that long showers and laundry the pump pulls a lot of water and the water level can drop.

    While getting my addition done the contractors hit the wire to the pump and couldnt get it fixed. They thought the breaker was bad so they disconnected the pump and wired it to the switch. When they reconnected it to the rope they lowered it only like a few inches into the water. In fact when I pulled it up to check the hose and lowered it with the same length of rope I had to shake the rope loose from slightly hanging up on the hose in order for it to go under the water level. Even with this shallow pump depth I was only running out of water after several loads of laundry and showers. This makes me think the well recharges quickly and the 3 foot width holds more water in less depth. I fixed the rope and now the pump is about 2 or 3 feet into the water and I have no issues.

    /-------------------------------------End of my rambling-----------------------------------------/

    VVVV An idea I was kicking around which might help you VVVV

    Not wanting to run out of water I considered running a pex discharge line back out and into the source well about 100 feet from my house. That way I would never pump more for the heat pump than the well could produce. I figured under normal use I would get rid of some of the recycled water through faucets, showers, and laundry. I could also install a desuperheater which could recycle the extra heat into residential hot water and hydronic radiant floor heat. I also considered a small, maybe 600 feet, loop field of pex prior to reinserting the water into the well. This would essentially bleed off a lot of heat into the soil without having to maintain a closed loop. Is this theory sound and could this possibly fix your problem?

    Thanks. Keep us updated.

    I am new to the forum and floated this idea in an older thread. The thread was older so it will probably be passed over. I am sorry if somewhat duplicating my response and post isnt socially accepted here.

    I currently have a shallow well on my property. I have considered a third heat pump for my addition if I can not make envelope improvements on my existing house to allow the air source system to be used. I have considered closed loop but eventually I could have as many as 3 small geothermal systems (over the next 10 years) on the loop. It makes sense to have 3 separate systems because the construction, insulation, and envelope dynamics are completely different on all three zones. Also 3 smaller systems are generally more efficient than one big 5 ton unit.

    Simple solution would be to tie a second pressure tank into my water system and add a pex manifold for the geothermal unit or units before the water softener for the rest of the house. I know softer water would be better for the geothermal heat pump but not for reinserting the water. My well is an older stone 3 foot wide well that hits water right at the 35 foot mark. The water level is pretty reliable all year round. Even when my builder had an accident, removed the pump, and put it in at only about 6 inches deep (I would be surprised if it was even that deep) I got decent recharge (hope that is the right term.) I am very hesitant to get a pump and dump system because it is an older well. In fact there are only 2 homes out of about 10 on the block that has not had one of the newer 5 inch PVC deep wells installed. I think they were probably sold on the deep well prior to trying things like installing a submersible pump with a larger pressure tank and not watering the lawn all summer long. Anyway, I still want to be careful.

    I also understand a big issue with putting the water back into the same well is the temp delta. Is there enough water in the well to prevent overall temp rise or loss before the earth absorbs the difference. This is also a real concern of mine.

    I might have come up with a solution, at least for me, and I want to get some opinions.

    I would first have a desuperheater equipped on whatever unit I chose for residential hot water and possibly radiant floor heat. This would be the first step in equalizing the out water temp. Second, the water out line on the heat pump would not just run directly out to the well 100 feet from the house. Instead, my plan would be to have a small loop field in the yard between the house and the well. I am thinking 600. I would put as much pex in as I could prior to the well. I would have about 100 feet between the house and the well to cleverly route the pipe at about 5 feet which is well below the 18 inch frost line. The water would have enough distance to be warmed or cooled by the soil prior to being placed back into the well.

    I know with closed loops systems you are looking at about 600 feet per ton. However, in this case you are not constantly circulating all of the water directly from the loop back into the system. In this case it is still being dropped back into the well with a rather large amount of water prior to being reused.

    Any thoughts on this system? Thanks for the help.

    Posts merged by admin
    Last edited by a moderator: Jan 18, 2013
  8. urthbuoy

    urthbuoy Well-Known Member Industry Professional Forum Leader

    Standing column well design may be an option; otherwise, no. But it sounds like you have a short water column, so that may not be an option.

    The numbers are unlikely to add up. You'll be drinking very warm water or freezing your well. Basically your heat transfer is really going to be your well recharge rate, and you stated that it is low.

    The desuperheater won't be changing that water temperature in the manner you are thinking.

    The long discharge line might add some ability to temper the water, but even if it adds 1 ton of capacity - what % of the load is that going to be?

    It is rare for open loops to even exist in ponds/lakes.
  9. Kogashuko

    Kogashuko Member

    In my case the system will only be 2 tons initially for just an addition. If that works out I will eventually / 5 to 10 year plan / replace the other two 2 ton units. Our heating and cooling needs here are weird. My current 2 2 ton units are on a 1900sft house. 90 % of the time they work great and are slightly oversized. Most of the time they do not spend very long on each hour. My utility bill also dropped significantly when I went from one 3 ton unit for the whole house to a second 2 ton unit for the first floor. Then when the 3 ton unit finally reached the end of it's life (air handler 25 years old and outdoor unit 12 years old it didnt make sense to to just replace everything) I replaced the ductwork. My utilty bills dropped even more.

    Now my issue the other 10% of the time in the deep summer or winter the 2 ton units struggle. The other night it was 30 deg outside, I had the thermostats set for 68 / 67, and the units remained on almost all night. Some of this is probably because of the inherent flaws of air source in colder weather and some of it is probably the need for even more insulation in the attic. I feel that even if I did improve this that it would not justify having smaller units. I would rather just install a dehumidifier if I need it for the summer.

    Finally, I also plan on installing humidifiers in all three units. The air is very dry in the winter even after having the housing envelope sealed even better when they replaced he siding. I found a solution by accident. When having the addition installed they covered the old dryer vent and I have to run it out through the floor. I didnt want to do this because I plan on moving the dryer and dont want a hole in what will soon be my pantry. So, while waiting for the electritian to come back and put breakers in the sub panel, I decided to try blowing the warm air into a fan which distributes it into the house. I dont intent to do this for long and I know it is bad but it made the house feel more comfortable, less dry, warmer, and the heat pumps seem to run less. I would think 3 humidifiers in the winter would probably add to a % of the well draw.
  10. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader


    You might want to start you own thread.

    You need to look at what you need for heat loss/gain and not just accidently fix comfort issues by trial and error. The errors could be very expensive, but it is your money.

    Dryers vented into the living space is not a good idea as you know.

    I do not get why you are think about adding 3 humidifiers, who add to the well draw. It should go the other direction.

    Last edited: Jan 25, 2013
  11. Kogashuko

    Kogashuko Member

    I started my own thread but it was substantually similar to this one and got merged.

    I might not have used the right wording "draw." I was referring to pulling water out of the well so that the well could refresh with water from the earth that is either warmer or cooler depending the mode the heat pump is in. As long as I am dumping water back it the water level will not change or at least it doesnt seem to in my well. I know this because the hose sprung a leak and was spraying the water back into the casing. Luckally, the well didnt continue to fill with more water from the earth and overflow.

    As for trial and error there are a lot of quirky things with this house that I need to fix anyway. Today I ripped up the walk up attic stairs and am replacing the 2 inches of fiberglass with r30 fiberglass batts. I am then going to rebuild the stairs 2 inches high and 2 inches farther forward to allow space for the batts without the boards from the stairs crushing them. Since the attic stairs are overtop of the main staircase in the house I should notice a big change in heat loss gain there. Unfortunatly, one person cant get all these little issues worked out before intalling HVAC equipment.
  12. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    One can do all of the mystery stuff with a little professional help.

    I will not sell HVAC stuff without a total plan.

  13. Well, the Only thing I taught the engineers at Ford was to only change one thing at a time. If you do more than that, and you fixed it, you won't know which one worked.

    Thermostat Lady

    And yes, I also know how to move BTUH
  14. Kogashuko

    Kogashuko Member

    Update. I am definitely going to try this with my addition. We have had a few cold days that are very cold for our climate. Outside air was 11 deg f and even with strip heat I could not get the house to warm up to above 60 deg. Testing the water coming out of the well and it was still 65 deg. Part of the problem is the fact that the addition is attached all the way down at the crawl up to the attic. The addition has no insulation other than what is on the existing wall. Heat is still being sucked out of the attic and crawl making heat loss faster than normal. All my ductwork is in the attic and crawl. Still... I think I would be much better off with a ground source running even a little less efficient than they are suppose to.
  15. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader

    Welcome back, Kogashuko.

    Either I could be PWI or english is not your first language. Unfortuanaly it is my only one. I know you are online so I am going back to the thread and reread what you have written to better understand what your needs are.


  16. Mark Custis

    Mark Custis Not soon. Industry Professional Forum Leader


    I have re-read your posts to this thread. It is unfortunate that the threads were merged, as you bring knowledge and experience to this discussion. Thank you for not giving up your quest for knowledge.

    I wonder where you are. If I knew it might help me help you with your project.

    I am sorry that I fail to really read issues with what we call standing column well geothermal systems. I have only worked on one. I like using closed loop system in either ponds or dirt. I worry about the world running short of drinking water...

    I do not know a lot of tech stuff about you type of system, but Water-pirate and Dan Callaghan do. We might ask the guy from Utah, Dewayne Dean. So what I do not know we can find out.

    I do know constructions, system sizing, and heat transfer.

    I know see that you are under construction and will be fixing heat loss issues as you go. I am sorry I missed that before.

    Waterpirate, (Eric) mentions a thermal valve which would allow bleed off of over or under heated well water to allow the natural replenishment you describe.

    Is it possible to send the voided, over temperature water some where?

    I hope I can help. I do not know all there is to know about being comfortable, but I am old enough to know how to find the solutions to problems.

  17. Calladrilling

    Calladrilling Member Industry Professional Forum Leader

    Your 3ft round well is called a "dug well". They are typically hand dug and brick lined as the digging occurred with shovels and lots of man power. They typically only have a few ft of water in them anyways ( imagine trying to a deep hole on the beach. At high tide). With my local knowledge of hand dug wells ( almost extinct here in NJ), I would think its going to change temperature way to fast.
    i am also very partial to closed loop systems too. I have personally a never worked on a SCW (open loop into same well) so I can not add too much help. I do know they have a temperature actuated dump valve to bleed off over heated/cooled water from the well.
  18. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    As everyone has said, the thermal capacity of that well is going to be low. It has also been my experiance that the ring wells also have a capacity issue if not connected to a natural spring. That would indicate that even if you planned to bleed off 50% of water pumped, the well may not support that in gpm.

    Most every SCW geothermal project shares the commonality of being constructed in rock, extremely deep, low standing water table, and low production. All those things make it conducive to operating a SCW.

    My current pet project is going to be construction of a 6X100 pvc well with 90 feet of screen. The anticipated standing water table will be around 10'. I have to know how much thermal exchange I can get with the groundwater by returning the water into the well at 100' and extracting it at 15'. A word of caution to readers! This is highly theoretical and if it fails I will be out next to nothing, your financial miliage would vary greatly.
  19. Kogashuko

    Kogashuko Member

    Its actually really weird how they dug these wells and currently I have seen nothing like it. My neighbors down the street had like 3 of these dug. My next door neighbors had 2 and the first didnt produce water so the second one was dug later. Since then almost all of them have had a deep, they said like 300feet, well dug. My guess would be that there is an aquifer somewhere around 30-40 feet down and that everyone was sharing it. Now it is just me. Anyway, when they dug these wells they used a rig with a thing that looked like a giant ogger bit. They then brought in truckloads of congrete pipe and sunk them down with a crain all the way down, well below the water level in mine, and then lowered a nonsubmersible pump down. The non-submersible pumps were dangled so that they would not pump more than 25 feet up. This is another problem I think. Since we have random water level changes here the water level probably just dropped below the mouth of the pump. In other instances where the pump was too low it probably covered the pump causing it to burn out. Either way I think there was some marketing involved which caused the neighbors to roll with new wells. Not that I wouldnt want a deep well...

    I need to measure the water depth in the bottom. The last guy that came to treat the water system also put some clorine in the well to kill bacteria. He said "you have plenty of water in there." I think I might be fine with a 50% bleed from a single unit anyway. Several years ago the inline filter on my well pump hose broke and water began gushing out of the hole. I didnt know what happened other than when I washed my hands before bed I noticed the water pressure sucked. The next morning I had no water from the faucet and found that my crawl space had taken on a lot of water. Luckally, most of it seemed to spray up against the crawl door and was sprayed outside.

    Anyway, it is not that I am opposed to a closed loop system but it just seems like it will be very complicated when and if I replace my additional air source heat pumps with ground source. At that point I would probably consider digging a deep well. Also, I would not be opposed to dropping the water used from that back into the existing well. Would not let the drinking water go to waste and I could easily use it as a lawn sprinkler if I needed to.

    Thanks for the help. I will let you all know the water depth and the results when I go this route. Worst case scenario I have to put in a loop field this summer.

    Oh I am located Northeast of Richmond Va.
  20. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    Being in possesion of a masters liscense for the state of Virginia, I can tell you that the well you have now is grandfathered and it is no longer legal to construct a well like the one you currently own. The deep wells were drilled because the ring wells either did not produce enough water to supply their distribution, or they got filled with bacteria and could not be treated, or both. I caution you about statements like " it has plenty of water". Says who and for what purpose, and for how long. It was an off the cuff remark, by some guy who prolly does not know geo from a hole in the ground. lol litterally. The devil is in the details. You need to do the design work based on number of degree days at full tilt and do a pump test/draw down test and see how much water you are really working with. If you proceed you may find the return water causeing the standing water table to rise, nothing in nature is equal, it may short out your pump again. I would move to a submersible with a cooling shroud below the water table if it were me. Again I advise caution here as what you are proposeing is doctarate level well and pump work, that may never work.

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