Results 1 to 25 of 25
  1. #1
    Thailand Expat
    thailazer's Avatar
    Join Date
    Jul 2010
    Last Online
    Yesterday @ 07:54 PM
    Posts
    2,000

    Well Downpipe Diameter

    Here is an intriguing question: If you have a pump rated for a maximum well depth of 8 meters and you have an infinite amount of water at 5 meters, does the pump have to work harder if you you use a 2 inch versus 1 inch down pipe? The head is the same so it seems it would be equivalent, however, if you look at the weight of water in the down pipe that the pump back flow valve has to support when the pipe is not running, the 2 inch puts a lot more force on that valve. That weight difference makes me think the pump has to work harder with the larger 2 inch down pipe. Straighten me out here if you will.
    Press On Regardless

  2. #2
    Lord of Swine
    Necron99's Avatar
    Join Date
    Feb 2012
    Last Online
    @
    Location
    Nahkon Sawon
    Posts
    13,025
    Hmm, with a 1 inch pipe it is drawing less water but for possibly longer?

  3. #3
    Member
    Join Date
    Apr 2009
    Last Online
    18-02-2019 @ 11:38 AM
    Posts
    126
    You are right, the 2 inch pipe puts more FORCE on the valve but the PRESSURE would be the same as with a 1 inch pipe. Your pump produces underpressure to suck up a column of water and that pressure will remain the same for any column size with the same height. And therefore the pump power required will remain the same too.

    What does affect you pump performance is disturbance of laminar flow of the fluid,
    so do not start with a large diameter pipe and reduce abruptly to a smaller size.

  4. #4
    Member roger77's Avatar
    Join Date
    Oct 2009
    Last Online
    15-05-2016 @ 12:08 PM
    Location
    CR
    Posts
    295
    Big pipe small pump
    small pipe big pump.

    as#3 the pressure is related to head only, big suction pipe less pipe friction.

  5. #5
    Thailand Expat
    Airportwo's Avatar
    Join Date
    Mar 2006
    Last Online
    Today @ 11:54 AM
    Location
    Flat Earth
    Posts
    3,553
    1" pipe or 10" pipe hydrostatic pressure is the same, gravity...

  6. #6
    lom
    lom is offline
    Thailand Expat lom's Avatar
    Join Date
    Jan 2006
    Last Online
    @
    Location
    Trapped in an old mans body
    Posts
    8,317
    Use the pipe diameter matching the pumps inlet and outlet holes, the mfgr would had made a 2" hole if that would had been more efficient for his construction.

  7. #7
    Thailand Expat
    DrAndy's Avatar
    Join Date
    Nov 2005
    Last Online
    25-03-2014 @ 05:29 PM
    Location
    yes
    Posts
    32,028
    the size of the pipe makes no difference to the amount of water that is pumped, unless the pipe is too small and restricts flow

    the pump merely has to lift the water the same height

    but why not use the diameter pipe that is recommended and fits easier?

    as for the pressure on the valve, it will be exactly the same; it is the height of the water, not the amount that causes pressure

    that has also nothing to do with the question of flow
    I have reported your post

  8. #8
    Thailand Expat
    VocalNeal's Avatar
    Join Date
    Jul 2007
    Last Online
    Today @ 10:25 AM
    Location
    Bangkok
    Posts
    11,144
    Use the same diameter as the pump inlet as has been said.

    Larger may stay larger longer if there is any build up but on the other hand the higher velocity of the smaller will reduce the likely hood of buildup.

  9. #9
    Thailand Expat
    Ratchaburi's Avatar
    Join Date
    Dec 2007
    Last Online
    Today @ 12:00 PM
    Location
    Ratchaburi
    Posts
    5,186
    If you have a pump rated for a maximum well depth of 8 meters and you have an infinite amount of water at 5 meters

    What size riser pipe will not a problem if it is larger.
    You would have a problem if the riser pipe was smaller.
    Your flowrate will depend onthe depth of the water you say 5 metres
    Maybe but the longer the pump runs without stopping that water level mite drop
    This would reduce the flowrate.


    http://inspectapedia.com/water/Private_Well_Pressure_Diagnosis.htm

  10. #10
    Thailand Expat
    thailazer's Avatar
    Join Date
    Jul 2010
    Last Online
    Yesterday @ 07:54 PM
    Posts
    2,000
    Thanks all for the excellent replies and information. The reason I am asking is that right now I am using a 1 inch downpipe in a 2 inch well casing, but I want to go with a completely sealed well and water system so I am going pull out the 1 inch down pipe and will put a 2 inch to 1 inch adapter on the top of the well casing and go to the pump with 1 inch pipe which is what the pump is configured with. Just wanted to confirm I am not doing something stupid. The well is 8 meters deep and has two meters of spiral slotted well screen at the bottom in water bearing sand and gravel. The water actually comes within 2.5 meters of the surface but I exaggerated those figures to make the question more clear. Thanks again for the help.

  11. #11
    Thailand Expat
    DrAndy's Avatar
    Join Date
    Nov 2005
    Last Online
    25-03-2014 @ 05:29 PM
    Location
    yes
    Posts
    32,028
    Quote Originally Posted by thailazer
    The reason I am asking is that right now I am using a 1 inch downpipe in a 2 inch well casing, but I want to go with a completely sealed well and water system
    why seal it?

    when you are drawing water, something needs to replace the water taken out, and that is usually air

    if that becomes impossible, then you will build up negative pressiure in the borehole (unless the water is flowing into the bore easily)

  12. #12
    Thailand Expat
    Airportwo's Avatar
    Join Date
    Mar 2006
    Last Online
    Today @ 11:54 AM
    Location
    Flat Earth
    Posts
    3,553
    Quote Originally Posted by DrAndy
    when you are drawing water, something needs to replace the water taken out, and that is usually air if that becomes impossible, then you will build up negative pressiure in the borehole (unless the water is flowing into the bore easily)
    Dr Andy that's rubbish, your sucking from a porous zone, negative pressure?
    your sucking, it's not flowing? Replacing with air? New theory?

  13. #13
    Thailand Expat
    thailazer's Avatar
    Join Date
    Jul 2010
    Last Online
    Yesterday @ 07:54 PM
    Posts
    2,000
    Quote Originally Posted by DrAndy View Post
    Quote Originally Posted by thailazer
    The reason I am asking is that right now I am using a 1 inch downpipe in a 2 inch well casing, but I want to go with a completely sealed well and water system
    why seal it?

    when you are drawing water, something needs to replace the water taken out, and that is usually air

    if that becomes impossible, then you will build up negative pressiure in the borehole (unless the water is flowing into the bore easily)
    I am sealing it as the water is potable and I don't want any way for bacteria to get in. No storage tanks for me which are always breeding grounds for lots of critters. The negative pressure you mention is impossible as the last I checked, there was lots of atmosphere pushing down on the aquifer!

  14. #14
    Member
    fiddler's Avatar
    Join Date
    Mar 2010
    Last Online
    19-06-2019 @ 08:09 AM
    Posts
    395
    My two brothers are plumbers and they taught me a long time ago:
    "You can't judge the depth of the well by the length of the handle on the pump"

    Something I always remembered (for some strange reason)
    Also: Shit runs downhill and payday is on Friday.

    Good luck with your well (and pump)
    I would put in a jet pump system (two pipes to go down to a jet valve)
    That's what I have in my home in the states. Works down to 100' (30 m)

  15. #15
    Thailand Expat
    Ratchaburi's Avatar
    Join Date
    Dec 2007
    Last Online
    Today @ 12:00 PM
    Location
    Ratchaburi
    Posts
    5,186
    The best well system is submersible pumps, it will deliver high pressure in shallow depth well or Deliver water from 90 metres 290ft deep well at a lowwer pressure.

  16. #16
    Mid
    Mid is offline
    Thailand Expat
    Mid's Avatar
    Join Date
    Aug 2007
    Last Online
    @
    Posts
    1,413
    Quote Originally Posted by Airportwo
    1" pipe or 10" pipe hydrostatic pressure is the same, gravity...
    Corect Answer .

  17. #17
    Thailand Expat
    DrAndy's Avatar
    Join Date
    Nov 2005
    Last Online
    25-03-2014 @ 05:29 PM
    Location
    yes
    Posts
    32,028
    Quote Originally Posted by Airportwo View Post
    Quote Originally Posted by DrAndy
    when you are drawing water, something needs to replace the water taken out, and that is usually air if that becomes impossible, then you will build up negative pressiure in the borehole (unless the water is flowing into the bore easily)
    Dr Andy that's rubbish, your sucking from a porous zone, negative pressure?
    your sucking, it's not flowing? Replacing with air? New theory?

    as I said, it all depends if the water is flowing easily (read that bit)

    if it does not then negative pressure is likely

    think about it

    if you take out more water than flows in, then there will be a drop in the pressure if the bore is sealed

  18. #18
    Thailand Expat
    Airportwo's Avatar
    Join Date
    Mar 2006
    Last Online
    Today @ 11:54 AM
    Location
    Flat Earth
    Posts
    3,553
    ^ doesn't work for me? if you have negative pressure you have a dry well, even if it's very porous for it to flow or be pumped you have to have pressure greater than hydrostatic.
    If you take out more water than flows in, there will obviously be a drop in pressure, if you seal the well bore, close it in, the pressure in the well will rise depending on the flow rate and porosity of the zone?

  19. #19
    Thailand Expat
    DrAndy's Avatar
    Join Date
    Nov 2005
    Last Online
    25-03-2014 @ 05:29 PM
    Location
    yes
    Posts
    32,028
    just imagine you are drinking out of a cardbox fruit drink with a straw

    as you suck the drink out, the box will slowly collapse due to negative pressure unless the straw hole is enlarged ( equivalent to the borehole not being sealed)

    now imagine the box is in a water container

    if the box has small pinholes that collapse will not happen so fast, but it will still happen

    that makes it more difficult to suck the drink out due to the negative pressure

    if the pinholes are enlarged (equivalent to more water flow going in) then it is easy to suck out the drink

  20. #20
    Thailand Expat
    Airportwo's Avatar
    Join Date
    Mar 2006
    Last Online
    Today @ 11:54 AM
    Location
    Flat Earth
    Posts
    3,553
    I can kind of see where you are coming from, I have been drilling holes for nearly 40 years and have never heard any body explain pressures quite like you have
    All zones where you produce from, be it water, oil gas... naturally breathe as you will always be "producing" from porous formations, having a bore open to the air is immaterial, if the formation psi is .433 psi/ft normally pressured the air will not have the force to enter the formation to replace ?

  21. #21
    Member
    Join Date
    Feb 2010
    Last Online
    Today @ 07:07 AM
    Posts
    428
    Dr Andy
    I congratulate you. I read this thread the other night and thought how can I easyily explain this situation and now reading your post I know so thanks for teaching an old dog a new trick.
    I must ask though, exactly what are you qualifications? That answer makes me think, Physics teacher?

    My response was going to along the lines of, on the suction side of a pump all you need to remember is the higher you get the harder you need to suck.

    And if you are sucking on a vaccuum like Monica was then you must suck really hard to get a result.

  22. #22
    Thailand Expat
    thailazer's Avatar
    Join Date
    Jul 2010
    Last Online
    Yesterday @ 07:54 PM
    Posts
    2,000
    I am with Airportwo on this one. If you have a producing well, you will not get to the point you are elluding to. On our well, we have pumped over 20 gallons a minute with no draw-down on an adjacent well 2 meters away. The aquifer is a good one. If you want to draw a vacuum you need to be in solid rock with no inflow of water anywhere.

    Finally answered my question in thinking through some of the replies. The pressure head is indeed the same in both cases but since it is in PSI, mathematically you can determine how much weight the larger bore is supporting. The pump suction does not care about that weight however as it starts to draw water as soon as it overcomes the pressure.

  23. #23
    Thailand Expat
    DrAndy's Avatar
    Join Date
    Nov 2005
    Last Online
    25-03-2014 @ 05:29 PM
    Location
    yes
    Posts
    32,028
    Quote Originally Posted by ootai
    I must ask though, exactly what are you qualifications? That answer makes me think, Physics teacher?
    no, I am not a teacher although I have needed to teach my daughters physics, maths and chemistry when they needed help



    Quote Originally Posted by thailazer
    If you want to draw a vacuum you need to be in solid rock with no inflow of water anywhere.
    not a vaccuum, negative pressure, as illustrated with pinholes in the box

    if your aquifer is flowing well then there will be no problem

  24. #24
    Member
    fiddler's Avatar
    Join Date
    Mar 2010
    Last Online
    19-06-2019 @ 08:09 AM
    Posts
    395
    Quote Originally Posted by Ratchaburi View Post
    The best well system is submersible pumps, it will deliver high pressure in shallow depth well or Deliver water from 90 metres 290ft deep well at a lowwer pressure.
    Unless you have a steel casing, then lightning is your big enemy.
    So expensive to replace.
    But, I agree it is a good option. quiet too.

  25. #25
    Thailand Expat
    DrAndy's Avatar
    Join Date
    Nov 2005
    Last Online
    25-03-2014 @ 05:29 PM
    Location
    yes
    Posts
    32,028
    ^a very expensive option for a shallow well

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •