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Thread: Converting constant-flow to on-demand irrigation

  1. #1
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Default Converting constant-flow to on-demand irrigation

    I draw water from the lake using a Flotec (I know...) FP5182-08 pump. There's an 80' 2" line from the lake to the dock, then a 10' rise, then another 80' 2" line to a manifold where various zones are configured and supplied via 1" lines. If the drought ever ends, the 80' line to the lake will be removed, and the rise from the lake to the pump will be a few feet. It's controlled manually -- zone(s) are turned on, and the pump is started.

    I'd like to convert to a microspray system with many more zones for precision water application. I'm pretty sure this will require water storage under pressure, rather than straight from a pump, and in any event my wife doesn't like having to fuss with valves and switches.

    So -- how best to do this, starting with what I've got?

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    Moderator valveman's Avatar
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    All you need is a pressure tank and pressure switch, as long as all the zones are large enough to keep the pump from cycling. If you have zones that cause the pump to cycle, adding a CSV before the pressure tank will fix that.

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    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    That's what I thought, but the pump seemed a little wimpy. Specs say 50psi max at 10' head, 7gpm. Once we get the sprinkler design done, we'll have more to go on. Thanks...

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    I draw water from the lake using a Flotec (I know...) FP5182-08 pump.
    Mikey, Mikey, Mikey, I thought you knew better.

    bob...

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    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    I do now. Bought this a long time ago, and (to its credit) it's still running... When it dies I'll give you a call. I'll probably give you a call anyway when we get the sprinkler system doped out, but it'll be a while.

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    See I knew you knew better.

    I'll be here as usual. Just stop in. By the way, since I'm retired (in name only it seems) I do leave out of here earlier now. 2:00 PM is late for me.

    bob...

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    In the Trades Bob NH's Avatar
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    If you can design your irrigation system to use some minimum flow at all times then you can use an irrigation pump that has a fairly flat curve and let it run all the time that the irrigation system is on.

    For example, the Goulds Irri-gator GT10 will provide about 45 psi and the GT15 will provide about 50 psi over a fairly wide range but will not overpressurize the system if operated at low flow. The characteristic is much like you would get with a CSV.

    Shallow well jet pumps have a pretty flat curve in the 50 to 60 psi range and shutoff heads that are well within the safe range. http://www.goulds.com/pdf/7300.pdf

    You can run them with small tank and a pressure switch set about 5 psi below the shutoff pressure and it will run continuously with low flow, but it will shut off if the pump is dead-headed for any reason.

    If you want more pressure you can use a two-stage pump such as the Goulds HSC10. http://www.goulds.com/pdf/BHSC.pdf

    I'm sure that Bob (speedbump) has a similar line of pumps. I just picked Goulds because the curves are readily available.

  8. #8
    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Quote Originally Posted by speedbump View Post
    By the way, since I'm retired (in name only it seems) I do leave out of here earlier now. 2:00 PM is late for me.
    Oh-oh, we've got a conflict. 2PM is early for me -- I'm not out of my jammies yet . I'm sure we can work something out...

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    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Quote Originally Posted by Bob NH View Post
    If you can design your irrigation system to use some minimum flow at all times then you can use an irrigation pump that has a fairly flat curve and let it run all the time that the irrigation system is on.
    Well, the design is a blank sheet of paper right now, but that gives us a design point to consider. One goal is to minimize turf areas, so almost everything will be micro-irrigated, and we can probably design the system to keep just the right number of drips, emitters, and sprays running at all times to accomodate the pump. The turf areas are the hard parts -- micro-irrigation is not recommended, and is in fact prohibited in some areas in Florida. Fortunately, we live in a laissez-faire kind of neighborhood where almost anything goes, but we're in a no-man's zone between two cities on annexing binges, so it probably won't last. If we can get a certified Florida Friendly Yard in place before that happens, I doubt they'll make us rip it up and plant St Augustine, as some hoity-toity gated communities have infamously done.

    Maybe this thread should be moved to irrigation & sprinklers?

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    Oh-oh, we've got a conflict. 2PM is early for me -- I'm not out of my jammies yet
    Man, you are retired!!! I'm going to have to get some advice from you on how to keep the Wife working the business while the retired old fart just lounges. So far, I haven't been too sucessful in that department.

    bob...

  11. #11

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    Be careful about using small sprays and lake water. A friend of mine did that and spent lots of time unclogging them. I can't remember how he solved the problem, but he was able to avoid adding a sediment filter.

    -rick

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    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Yeah, this is typical central Florida lake -- mesotrophic, with Secchi depths of around 6'. I'd love to know how he did that without a filter, but I'm going to have to account for it somehow.

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    In the Trades Bob NH's Avatar
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    A swimming pool sand filter without the clarifier chemicals should be adequate for collecting the algae before they get into your system. Maybe you can find a used one at a yard sale. You can dump the backwash into some place where you need a little more water so you don't waste it.

    A pool filter needs a fairly high backwash rate so you need a good size pump. A shallow well jet would probably not be adequate.

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    That's what I use in my Tree Farm. Two large Sand Filters with Multiport Valves for backwashing. It keeps the little bits of sand and lime rock from clogging my Micro Jets. Just don't try to go much over 40 lbs with Pool equipment. Most of it is rated at a maximum of 50 lbs.

    bob...

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