new system design opinion

Discussion in 'Irrigation' started by jabbo, Jun 28, 2005.

  1. jabbo

    jabbo LawnSite Member
    Posts: 215

    If you could design a system from scratch before the well was dug on an acre of centipede what gpm's would you tell your well guy.
     
  2. sildoc

    sildoc LawnSite Silver Member
    Posts: 2,925

    as much as you can afford. I have talked to a well driller before. There is an art to their science, however there is only a certain amount that mother earth is going to give up. That will vary as to where the property is located.
    We had a well on the ranch that cost us 48000 in 1985. It average flow is 40000gpm. The guy down the road less than a mile put in a well at the same time. He only gets 300 gpm. He went deeper and only got 100 gpm more and it cost him almost 100000 grand. We have since sold water rights and lease out the property but my point is that it will vary on what you can get and your well driller can tell you oh we can get you x amount of gpm but what is the cost and how deep is he going to have to go?
    There are several hundred wells drilled a year that don't even have a 2gpm rating or better.
     
  3. bicmudpuppy

    bicmudpuppy LawnSite Silver Member
    Posts: 2,781

    Very sound advice. Here in my location, within 10 miles, a "good" well might bring 10gpm. Other spots will have less than 5gpm. Many rural homes get placed on cisterns that wells fill almost 24/7 so that the house pump can run 5+gpm to run showers, etc. from the cistern. I have recomended wells to fill ponds in the same fashion so we could irrigate from the pond. Run the fill pump/well for 20+ hours a day so you can pump from the pond for 6............ Hopefully your in better water country than I, but a well expert will be able to give you good advice.
     
  4. jabbo

    jabbo LawnSite Member
    Posts: 215

    You really did not answer my question. Lets say that the well guy says that he can put a 4" well in for "x" amount of dollars and I have the option (for that same amount) to have a choice from 10 gpm's to 30 gpm's what would be your choice. We don't have many problems with wells going dry. As a matter of fact we have some wells that are only 40 to 50 feet deep with all the water you want! Again this is for 1 acre of centipede. The reason I am asking is because I already have a 1.5 horse that produces about 13 gpm at 50 psi and I am debating on if I want to spend that much time a week watering because I am not going to be able to put alot of heads on a zone. Also the heads are not going to be able to have that much flow/pressure. So I was thinking before I even start designing this system that in the long run (as far as watering time per week) I would be better off to change out my well pump! Sorry for such a long post.
     
  5. sildoc

    sildoc LawnSite Silver Member
    Posts: 2,925

    I am not even sure you are asking this question. If you can have 30gpm why choose 10? I find that if it is the same price there really is no question of what to do. You will need it later. Any ways a 30gpm well today might be the 10 gpm well in the future and visa versa. Go large work on the pressure thing later.
    Now why the larger? Because most likely you are filling a tank also. Your pump only has to work half the time to fill the tank on a higher gpm well where if you have a lower gpm well you are going to have to replace the pump sooner because it is working harder.
     
  6. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 48,014

    There is no real economic motivation to go changing pumps or drilling wells, if the existing well and pump can supply the existing needs of your lawn. (and yours can do so, if you bother to run the numbers) By all means, if you care to, design a system with ability to use more water (by replacing existing nozzles with larger ones) in the event that you do replace a pump with a more powerful one. Choose larger pipe sizes, and there won't be excessive flow losses when a new pump is put in place.
     
  7. Wet_Boots

    Wet_Boots LawnSite Fanatic
    Posts: 48,014

    If you want to install a larger pump, and your well can supply the water, then nothing is stopping you. It's only money. What you have yet to state is what it is that requires you to obtain more water. You could have less than half your current gallons per minute, and still water an acre. I've had to work with even less than that, and still managed to cover the area. Some more details, please. Is your soil sandy? Extremely sandy soil drinks in much more water than normal soil will. Is there some absolute limitation on the hours that the sprinklers can be running? Pin down some of these variables, and and some informed advice might follow. For now, all you have is some vague feeling that you want more. Who doesn't?

    Compared to what you'll get back on sprinkler system savings, a new pump here won't be paying for itself. And you do want to consider the short-cycling of a more powerful pump on your existing pressure tank. A pump puts out X gallons per minute maximum. The pressure tank has a Y gallons minimum drawdown. Run the numbers, and you will obtain Y/X minutes (minimum) between pump starts. - steel pressure tanks can rust out. If your tank may someday give out, adding an additional one, maybe a fiberglass model, will add needed drawdown as well as providing some insurance.
     
  8. jabbo

    jabbo LawnSite Member
    Posts: 215

    Ok, I'm going to try and make this as short as possible. First of all, I really appreciate the help and I would really like for you to walk me thru this so that I can decide what I need to do. I have a little over an acre of really sandy land with centipede on it. I have about 13 gpm @ 50 psi as far as I can figure. I want to use mainly hunter stuff and have been doing some figuring using one of there books. As far as I can tell with that flow I can put about 4 or 5 pgp's per zone using #5 nozzle for 2 gpm. If I use head to head spacing I am going to have to space them about 30 ft. apart. I sat down and kinda drew out some heads and spaced them out for 30 ft. I came up with around 80 heads( I know some of this "figuring" is probably wrong so that is why I am asking all of the questions). With that many heads I am going to have around 15 or 16 zones plus the flower beds. Going by the manual a #5 nozzle will produce about .15 tenths in an hour for a full circle. At that rate it will take me running my system all night long all week long just to water over the yard one time. Then I'll have to start all over again. And like I said please correct any of this if it is wrong. So I was thinking about the long term $ amount and was going to icrease my flow so that I had about twice as much flow so I could space the heads out further and put out more water at the same time. It would be a cost increase at first but after that I would not have to run my system near as long to cover the yard. I'm trying to think about 10 or 15 years down the road. I need all the advise I can get so if you think I don't need to change out my pump and will not have to spend all night watering then shoot me some numbers or scenarios. Sorry for the long post.
     
  9. williamslawn

    williamslawn LawnSite Member
    from SC
    Posts: 202

    We like to have 30GPM so we can use 8 heads a zone with 3.0 nozzles. I set my pumps to run constantly while irrigation is on. But as someone else said if you can only get 13 GPM then you will need to design your system on the amount of water you have.
     
  10. jabbo

    jabbo LawnSite Member
    Posts: 215

    Thanks for the reply. I also did some "figuring" after I decide to go to 30 gpm's and found that I could even use 4 or 5 heads still but would be putting down more than three times the water and also could space the heads at like 45' instead of 30'.
     

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