help sizing pump

Discussion in 'Pumps and Tanks Well Forum & Blog' started by ndwolf, Jan 16, 2014.

  1. ndwolf

    ndwolf New Member

    Messages:
    16
    Location:
    nd
    Last year i had a new well dug and now i want to build the pump house and install a well pump. i could use some guidance on selecting a proper pump. ill give the info i have for the well and maybe someone can help me select the proper pump. i thought about just hiring someone to put the pump in and then take it from there but id still like to have a rough idea what pump size is required so that i dont get screwed by the contractor.

    this info came off the well diggers reciept.
    130ft deep, 92 ft is the water level, perferated pipe set at 110ft to 130ft, 4.5 inch casing plastic
    it also states that 8 to 10 gpm pumped for 1hr with water level then at 126ft.

    From the well pump house there is roughly 160 ft of 1 inch poly to where the house will be. there is also about 6ft of elevation from the well shed to where the house will be. It will be a 2 bath house with only 2 people living permantly there. I also hope to add a small barn and water for a few horses and a few cattle and a small garden.

    with this info can i figure out the right pump size to get? any help would be welcome. thanks!
  2. valveman

    valveman Moderator Staff Member

    Messages:
    4,466
    Location:
    Lubbock, Texas
    Sounds like your well will support a 3/4 HP, 10 GPM pump. If you need more water than that, you would need to put in a storage tank with a booster pump. But you would be surprised how much you can do with 10 GPM. If you start early and stay late you can do a lot of watering with 10 or less GPM.
  3. ndwolf

    ndwolf New Member

    Messages:
    16
    Location:
    nd
    i read one of your posts that said the pump should be set above the screen does that mean in my well with the perferated pipe set at 110 to 130 ft i would set the pump at 110 ft. or could i set it alittle deeper. also ive been reading about the cycle stop valve and was wondering if that could be applied to this well or would just a large bladder tank and pressure switch be better.

    Also what is best used to protect the pump if the water level drops below the pump intake as it seems that this well can be pumped low pretty quickly if i understand the diggers pump data correctly. thanks for your input.

    forgot do you have a special brand of submersible you like over others. thanks again
  4. valveman

    valveman Moderator Staff Member

    Messages:
    4,466
    Location:
    Lubbock, Texas
    Since the well test showed a pumping level of 126’, you will need to put the pump as low in the well as you can. In our area we would have use 5” casing so you could install a 4” flow inducer sleeve to keep the motor cool. However, in your case you will just have to live with what you have as a flow inducer won’t fit in 4.5” casing.

    A Cycle Stop Valve and a 4.5 gallon size tank will do a much better job than a large tank without a CSV.

    I don’t like the Pentair version of the 10 GPM pump as the amps don’t drop when using a CSV. Goulds will drop a little and a Grundfos will drop a lot. But that won’t make much difference with just a ¾ HP motor.

    A Cycle Sensor is a good device for Dry Well protection and works well with a CSV when other devices will not. It will also protect against a rapid cycle condition, which occurs if anything goes wrong with the CSV, tank, or pressure switch.
  5. ndwolf

    ndwolf New Member

    Messages:
    16
    Location:
    nd
    thanks for taking the time to answer my questions. wish i would have known about the 5inch casing i would have went with that. the mrs asked the well digger what depth to set the pump at and he said around 120ft so from your input and his staement ill put it at 122 and see how it works.
    i will go with a CSV and a tank(although maybe a little larger than4.5 gallon)

    and i will definetly go with the cycle sensor. are all these cycle sensor devices pretty similiar or is there some to watch out for. i did look at the ones at cyclestopvalves.com.
    so i guess a goulds like this should work
    http://www.aquascience.net/submersible-pumps/index.cfm?id=373
    thanks again for your advise
  6. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,980
    Location:
    NW Ontario, Canada
    Since they managed to pump it down to 126 in an hour, 122 might run dry sooner. You should consider a cycle sensor to protect against the well running dry.
  7. ndwolf

    ndwolf New Member

    Messages:
    16
    Location:
    nd
    yea im also sure it will run dry sooner at 122ft than it would at 126ft. i just dont know what the pros and cons are for putting the pump almost all the way at the bottom of the well (i.e. 126ft.) do wells silt up the last few ft or what about cooling the pump is it harder to cool at the bottom? things i just dont know dont know. would there be away once i bought the pump to drop it down and start pumping and then be able to determine what the best depth would be?
  8. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,980
    Location:
    NW Ontario, Canada
    I suggest you tape a length of 1/4" tubing to the downpipe so that you can use it later to monitor the water level. There is a possibility that the well will develop over time and produce more GPM.

    There is also the chance that the bottom could silt up depending on the formation and the size of screen they used. The lower the pump, the less flow there would be passing the motor so less cooling. When they drilled, they might also have bored a couple of feet into the bedrock or into a non-permeable layer and so there might not be any flow through the last few feet of screen anyway. If the motor got buried in silt, that too can affect cooling.
  9. ndwolf

    ndwolf New Member

    Messages:
    16
    Location:
    nd
    how can a 1/4 inch tubing be used to monitor the water level
  10. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,980
    Location:
    NW Ontario, Canada
    Put a Tee on the top of it with a schrader valve and a low pressure gauge. Pump air into it and read the gauge. Formula is .43 PSI per foot.
  11. VAWellDriller

    VAWellDriller Member

    Messages:
    171
    Location:
    Richmond, VA

    You get a Grundfos 3"pump and put it in 3" sleeve, and easily fit that in your 4.5" well. Given the relatively low static, you probably should set the pump as deep as you can, and this would still ensure proper cooling.....they also come with built in run dry and over/under voltage protection built in the motor...you can use them with a csv if you want.
  12. ndwolf

    ndwolf New Member

    Messages:
    16
    Location:
    nd
    that sounds like a good idea
    could you direct me to some place that sells that model pump and sleeve. thanks
    is this what your taking about
    http://www.aquascience.net/submersible-pumps/index.cfm?id=1296
    Last edited: Jan 18, 2014
  13. ndwolf

    ndwolf New Member

    Messages:
    16
    Location:
    nd
    thats very interesting . how much air do you pump in though still not sure how this works.
  14. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,980
    Location:
    NW Ontario, Canada
    As much as it takes. The surplus comes out the bottom end. That is what tells you (using the math) how many feet of water there is at the time above the bottom of the tube.
  15. ndwolf

    ndwolf New Member

    Messages:
    16
    Location:
    nd
    now i think i understand. you pump air in until the gauge doesnt go up any more because the air is escaping out the bottom and then whatever the gauge reads at that time you divide that by .43 and that tells you how many ft of water there is.
  16. valveman

    valveman Moderator Staff Member

    Messages:
    4,466
    Location:
    Lubbock, Texas
    As I have said before, Franklin motors have been shortened up so much that a ¾ HP is only 10” long. They claim the motor being so short doesn’t need a flow inducer sleeve as there will still be some circulation just 10” below the pump suction. This maybe plausible and I am sure it works, there is just not as much circulation as when using a sleeve. I believe as long as the motor is not sitting in sand or set below the perforated casing it will be good enough.

    The 3” pump is a good idea, but is considerably more expensive and spins 10,600 RPM compared to 3,450 RPM of the 4” pumps. In the Grundfos engineering manual they claim doubling the pumps RPM will shorten the life by half, and I believe this to be fact.

    However, the 3” pumps do not need a flow inducer sleeve. They actually have a little pump inside that circulates the fluid through the motor for cooling. The electronics in this type motor would not stay cool enough without this cooling system. The 3” pumps are also a little longer than 4” pumps, so you would not be able to get the pump intake set as low in the well with a 3” compared to a 4”. When your well is 130’ deep and the pumping level is 126’, the deeper setting of the pump intake is important.
  17. ndwolf

    ndwolf New Member

    Messages:
    16
    Location:
    nd
    some good insight . thanks
    im aware of longevity issues relating to rpm speed from operating gen sets and higher rpm never last as long as lower running ones do. Probably is the same for pumps. i noticed they do sell a flow sleeve for the grundfos 3 inch pumps. dont know why though.
    the 4 inch goulds pumps seem to have Centripro motor not Franklin motors unless franklin makes centripro motors also. i dont see any grunfos 4 inch pumps only 3 inch.
    when talking about what depth to set the pump at do people refer to that number in referance to where the intake of the pump is set at or in referance to the top or bottom of the pump?
    If putting a 4inch pump in a 4.5 inch casing does it matter that there is only .25 of an inch or so around the pump once in the hole. i read that most 4 inch pumps wont fit into a 4 inch casing although this is a 4.5 inch casing ( or at least thats what the reciept says, ill have to make sure by actually measuring it)

    Looking at the diggers reciept i noticed that he dug to 140 ft total but set perferated pipe from 130 to 110 ft. so when you commented that as long as the pump isnt set below the perferated pipe it should be ok if the pump is set at 126ft since that is still 4 ft above the perferated pipe end.
    thanks for all the input from everyone.
  18. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    3,980
    Location:
    NW Ontario, Canada
    If using a sleeve that is completely sealed at the top, it effectively lowers the intake to the bottom of the sleeve.
  19. craigpump

    craigpump Member

    Messages:
    941
    Location:
    ct
    Franklin does not make Centripro motors.

    Grundfos does make a 4" pump, but their motors are questionable.

    Actually, a 4" pump is 37/8" in diameter so it will fit perfectly in 4" ID PVC.
  20. VAWellDriller

    VAWellDriller Member

    Messages:
    171
    Location:
    Richmond, VA
    If a Grundfos 3"pump is set totally top feeding situation, it will overheat and shut itself off....I've personally seen it happen, and putting a piece of 3" DWV pipe cured it instantly. As far as the high speed of the Grundfos, yes it's fast, but they seem to have designed every part to work that way; I've put in scores of them oldest being about 7 or 8 years, and never had even 1 fail for any reason at all. It's not my pump of choice because of cost and limited selection, but in situations like this where you cannot install a sleeve on a 4"pump, and want to set it deep in the screens where it may not get good cooling flow;its a good choice. If the couple inches it is longer than a 4" motor are a problem with the depth setting, you've got a lot bigger problems. I have never used their variable speed controller, so I can't offer an opinion on that. As Craig said, all 4" pumps as made to fit 4" pipe....(sch 40 pipe). Any reputable driller or pump service could sell you a Grundfos pump.
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