Dug well pump questions

Discussion in 'Pumps and Tanks Well Forum & Blog' started by MikeSS, Apr 14, 2014.

  1. MikeSS

    MikeSS Member

    Messages:
    32
    Location:
    San Diego, CA
    I've gone through the shallow well questions & answers and don't see exactly the same situation so I'll try to be clear without being overly wordy.

    I bought my property 13 years ago and was planning on drilling a well with one of those rigs like you see advertised in Popular Mechanics - HydroDrill I think it is/was called. I never followed through for various reasons but did buy a Harbor Freight Shallow Well pump on sale. It is blue and branded Central Machinery. 3/4 hp motor, 5 gal bladder tank, 1 inch inlet & outlet. Since I bought it it's been in the box, unopened, since 2004.

    A couple years ago I discovered I have an old (probably 1950 or so) dug well that was covered up. It had a concrete lid that cracked and fell into the well - which is how I found out I had the well. I recently had a well contractor rebuild the cover and seal this 54" diameter well, installing a 10 inch casing in the center with locking cap.

    The well is 18 feet deep and water level is 7 - 8 feet down from ground level - so there's 10 feet of water.

    I realize the HF pump is "junk" (I've been learning about wells and pumps off the internet for the last couple weeks) but I'm thinking since I already have it why not give it a try. It will be used only for irrigation. I won't need to raise the water any higher than ground level, although I'm thinking a storage tank might be a good idea someday. I'm 350 ft. above sea level.

    My first question, is this pump a jet pump or a centrifugal pump, if anyone knows? Looking at the parts diagram I don't see an impeller with vanes (like on a car water pump), but there is a flat disc-looking thing that's labeled an impeller - but it's not obvious to me from the drawing how it works . . . and although I grasp in theory how a jet pump is something like how a venturi in a carburetor works, I can't tell from looking at the exterior of a pump what a jet pump looks like.

    Second question, would I make it easier on the pump to use a 2 inch suction pipe going into the well? Or, since the inlet is 1 inch, does that mean the pump needs to stick with that diameter pipe since that was how it was designed? I want to make things as easy on the pump as I can.

    I've learned about foot valves so I'll be using one, along with a nice big "lake screen" or similar device to keep any junk from getting sucked into the inlet - even though I know the foot valve also has a screen. I'm also thinking a "wye strainer" placed in the line just before entering the pump would be a good idea? Or would that add too much resistance?

    I keep reading about the advantages of a CSV - would one of these in my application be of value? If it will keep the pump from cycling off and on a lot when I'm irrigating then it would be of value, but I don't know yet if my pump will be cycling on and off . . . but it's a question anyway in case someone would take a stab at advising me on this. My thought at this point is that I'll be turning on the well when I want to irrigate and turning the pump off when I'm done. This is a nice simple system I can understand at this point. I might get into fancier things once I've learned more about how things work.

    I guess that's all my questions at this point. The main one is do I go to a 2 inch downpipe to reduce pipe friction or for some other reason, or should I stick with 1 inch or maybe 1.25"? I've been learning a lot about wells and related issues lately but still don't have standard concepts fixed in my brain yet.

    Thanks,

    Mike
  2. Texas Wellman

    Texas Wellman In the Trades

    Messages:
    550
    Location:
    SE Texas-Coastal
    Drop a 2" line down in the well equipped with a foot valve and use a gasoline pump (trash pump) to test the well. If it will pump with the 2" pump then you can hook up the jet pump. My bet is that the well doesn't make any water.
  3. MikeSS

    MikeSS Member

    Messages:
    32
    Location:
    San Diego, CA
    I'm on the edges of a river and the water table for my area is about eight feet down. It's alluvial all around me. Why wouldn't the well make any water? Do dug wells "seal" themselves over time?

    Thanks for answering my question about what type of pump this Harbor Freight pump is. Jet pump. How about the question about what is the best diameter suction pipe to use?

    I've thought about renting a trash pump and doing just what you said, not only to test the well's recharging capacity but also to just clean it out a little of small debris.

    Thanks,

    Mike
  4. Texas Wellman

    Texas Wellman In the Trades

    Messages:
    550
    Location:
    SE Texas-Coastal
    1" on the inlet is fine. Use whatever the inlet fitting is. Most jet pumps are 1.25" but it would not be impossible to get one that is 1".
  5. Texas Wellman

    Texas Wellman In the Trades

    Messages:
    550
    Location:
    SE Texas-Coastal
    As far as the well making water, just because the hole is filled with water does not mean that water will freely flow into the hole enough to sustain a pump. If the hole only fills at 1 GPM and you're pump makes 10 GPM it won't be able to sustain the water.

  6. MikeSS

    MikeSS Member

    Messages:
    32
    Location:
    San Diego, CA
    I measured the inlets & outlets and came up with 1 1/4", then later saw in the documentation that it lists the inlets and outlets at 1 inch. Whichever it is I'll stick with that.

    Thanks for answering that fundamental question about what size downtube to use.

    Mike
  7. MikeSS

    MikeSS Member

    Messages:
    32
    Location:
    San Diego, CA
    I've still got a question chewing on my brain. I've verified that my inlets and outlets are 1 inch. The question I've got is what would be the effect of going to a larger diameter pipe on the downtube?

    Maximum flow with this 3/4 HP Harbor Freight Shallow Well Pump is 898 with no vertical lift." The book for it says "maximum vertical lift is 26 feet" and that the GPH will drop the closer to 26 feet I get. The book continues "Systems with larger vertical components should have larger diameter piping." My drop pipe intake will be at no more than 18 feet which I think qualifies me as having a system with a "large vertical component." We're talking shallow dug wells here so 18 feet is significant if the limit is 26, so I'm wondering what effect the larger pipe has on things. Does it reduce friction between the water and the pipe interior? Does it make it easier on the pump to pump water in some other way and if so what way? That's my question.

    From one inch I can go 1¼", 1½", or 2". Or even larger I guess, but those choices seem the practical ones. Which one would be best? And why?

    Learning,

    Mike
  8. valveman

    valveman Moderator Staff Member

    Messages:
    4,549
    Location:
    Lubbock, Texas
    The larger the suction pipe the lower the friction loss and the better for NPSH. But with that size pump it probably won't help to go any larger than 1 1/4".
  9. MikeSS

    MikeSS Member

    Messages:
    32
    Location:
    San Diego, CA
    Thanks for taking the time to reply Valveman.

    I called my local Harbor Freight to talk to them about NPSH but she put me on hold :)

    Would putting a Y-strainer in the line just before the pump inlet add a significant amount of flow resistance? It's probably not necessary but am wondering about it anyway. They'll be a large triple-mesh lake strainer with a foot valve inside that, so not much will get through and what little does can just flow on through the pump I guess. It's for yard irrigation, not drinking.

    The main question from the beginning has been to determine the optimum diameter tubing going down into the well.
  10. valveman

    valveman Moderator Staff Member

    Messages:
    4,549
    Location:
    Lubbock, Texas
    Now that’s funny, I don’t care who you are.

    The less restriction on the suction line the better. Strainer may be OK until it gets some debris in it, which is the reason for it. Better to just let that debris go through the pump. Use 1 ¼” suction line.
  11. MikeSS

    MikeSS Member

    Messages:
    32
    Location:
    San Diego, CA
    Thanks again.

    Mike
  12. MikeSS

    MikeSS Member

    Messages:
    32
    Location:
    San Diego, CA
    Just getting back to my well . . . it says in the pump book to put a gate valve on both the intake line and the output line, and to install these next to the pump inlet and outlet.

    Can someone tell me why I need a gate valve on both sides? I can imagine that water from a storage tank would siphon back through the pump once the pump is turned off, but seems like one gate valve, inlet or outlet, would cover this issue. Why on both sides?

    Thanks, Mike
  13. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,265
    Location:
    Maine
    I never put one on the inlet.
  14. MikeSS

    MikeSS Member

    Messages:
    32
    Location:
    San Diego, CA
    Thanks. I'll just put one on the outlet, a ball valve, unless someone chimes in with a reason to put one on the inlet as well.

    Mike
  15. valveman

    valveman Moderator Staff Member

    Messages:
    4,549
    Location:
    Lubbock, Texas
    A ball valve on the outlet side is all you need. But the water will go back to the cistern when the pump shuts off if you don't have a check valve somewhere. A check valve can go on either the suction or the discharge of the pump.
    craigpump likes this.
  16. LLigetfa

    LLigetfa DIYer, not in the trades

    Messages:
    4,138
    Location:
    NW Ontario, Canada
    My guess is so that the pump can be removed to service it. Gate valves however, are not a good choice. Ball valves are a better choice.
  17. craigpump

    craigpump Active Member

    Messages:
    1,031
    Location:
    ct
    Harbor Freight?
    Gate valves on both sides of the pump?
    Must be rough translation from Chinese...
  18. MikeSS

    MikeSS Member

    Messages:
    32
    Location:
    San Diego, CA
    Thanks. I've got a foot valve at the bottom of the downtube.

    Tomorrow is the big day! Everything is in place. I had it pretty much done today but thought I'd wait a day for the Red Hot Blue Glue to cure on the joints. I used two 45's instead of a 90 to go from the vertical downtube to the horizontal piece going to the pump, about three feet away - trying to make an easier turn as the water comes (hopefully) up the pipe. I put a union on that horizontal stretch so I can disconnect the downtube from the pump in case I need to pull the downtube to clean the inlet screen.

    I'm currently just got a hose on the gate valve on the outlet side. If the pump draws water I'll then run the hose to an elevated tank storage reservoir that I can use for gravity-fed irrigation. My plan once the elevated reservoir tank is in place is to run the pump until the storage tank(s) are full then turn off the pump. I don't understand at this point what use the bladder tank and pressure switch is - I hope they don't get in the way of what I'm thinking to do.

    The pump, BTW, is 12 feet above the top of the water level in the well. Below that is 9.5 feet of water and the well is almost four feet across. I'm curious to find out, if my pump draws water, how long it takes the well to recover once I draw the water down to my foot valve inlet. I've got the downtube footvalve inlet sitting about two feet off the bottom of the well to try and avoid drawing sediment.

    So tomorrow, with everything connected, I'll fill my downtube with water from the prime inlet hole and hit the switch and see how this Chinese marvel works.

    Mike
  19. MikeSS

    MikeSS Member

    Messages:
    32
    Location:
    San Diego, CA
  20. MikeSS

    MikeSS Member

    Messages:
    32
    Location:
    San Diego, CA
    Well, no water coming out. The downpipe is full although that could be from the prime I put in and not from suction. The pressure gauge is showing zero, not even moving off the peg.

    This pump has sat in the box for eight years or so in the garage, although it sounds like it's running like it's supposed to. Could the attached tank with the diaphragm inside it have something to do with the pump not building pressure? Maybe I should just go buy another pump. One without a tank. I can't figure out what the hell I need the tank, pressure switch, etc. for anyway. I just want to pump water out of the well and fill up a reservoir.

    Thanks,

    Mike
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