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Thread: Designing a single well and pump system to supply both irrigation and treated water

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    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Default Designing a single well and pump system to supply both irrigation and treated water

    In another thread Dittohead mentioned (http://www.terrylove.com/forums/show...l=1#post384090) that "Irrigation should not be fed off the softener."

    With a single well, pump, and pressure tank, how do you plumb and wire the components so that the chlorine dose to the treated-water flow doesn't get adversely affected by the irrigation use? The chlorinator pump is commonly wired in parallel with the pump, but with an irrigation load, the chlorinator pump would run when irrigation water is flowing, resulting in overchlorination. Controlling the chlorinator with a flow switch in the treated-water line wouldn't detect the many small flows that make up the treated load, resulting in underchlorination. A flow switch in the irrigation line to turn off the chlorinator would help, but if there's a large treated load at the same time, underchlorination results. An extra pressure tank, flow switch(es), and check valve(s) could minimize the problem, especially if the chlorine is injected prior to the treated-side pressure tank, but many pro's don't like that approach. Sensing the chlorine level downstream of the contact tank and using that to control the chlorinator is much better, but introduces a potential time lag in the dosage, and probably costs a ton of money. A small circulation loop across the contact tank feeding the chlorine detector solves the time-lag problem, but doesn't help the ton-of-money problem. A sensitive flow meter controlling a variable-dose chlorinator comes close as well, but also misses small flows, and is also pricey. Any ideas/suggestions?
    Last edited by Mikey; 06-28-2013 at 04:33 AM. Reason: typo

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    Water systems designer, R&D ditttohead's Avatar
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    A few options are available. My preference is a simple Chemilizer or similar style pump. As long as it is not in earshot, these are noisy.

    Check out this video, it is a great cutaway display of how these non electric demand style pumps work.

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    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Thanks; interesting, but not very informative without narration. So I match up the pump injection ratio, average flow (maybe), and chemical concentration? Simple, and not terribly expensive. The installation and operation manual has some inconsistencies I've got to talk to them about, but I'll have to wait until next week. How come these aren't more widely recommended/used?

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    Water systems designer, R&D ditttohead's Avatar
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    They are very common in the irrigation and carwash market. They have not gotten wide acceptance in the water treatment industry. Iam not really sure why. Everytime one of our customers is willing to switch, they never go back to the older pumps. The ease of installation, the potential to run a bypass so a small pump can work on a larger line, etc, the low intial cost, no electricity, easy plumbing, these really are a great product. Many of the large distributors are starting to carry them finally over the past few years.

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    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Quote Originally Posted by ditttohead View Post
    ...the potential to run a bypass so a small pump can work on a larger line...
    How does that work? I've got 1" lines throughout, but this pump has 3/4" fittings. Installing it as directed in their manual and closing Valve A as directed

    Name:  Chemilizer.jpg
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    will result in restricting flow to the 3/4" limitation. You could regain full capacity and still meter the chlorine precisely by putting a calibrated restriction in the 1" line and adjusting the chlorine concentration upward, but that's well above my pay grade.

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    Water systems designer, R&D ditttohead's Avatar
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    Thanks, perfect diagram. This usually works for higher flow applications but has tends to become less accurate in fluctuating flow conditions. I prefer to have all of the water run through the pump if the water flow is going to vary. If it wont, then this works great.
    They make this pump design in larger sizes.

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    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    I wonder why it works at all. There is essentially no differential pressure between B and C to drive the flow through the pump motor. In my case, it probably doesn't matter that much -- I'll just accept the 3/4" flow limit.

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    Water systems designer, R&D ditttohead's Avatar
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    The flow would be restricted at point A. The majority of the water would be forced through the pump. This bypass design really only works if you have a set flow rate. If you have a 20 GPM pump, you would open valve A to allow 12 GPM through it, and 8 would have to go though the Chemilizer pump.

    They make these pumps in larger sizes or multiple pumps can be used.

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    Aspiring Old Fart, EE, computer & networking geek Mikey's Avatar
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    Thanks -- I thought something like that, but that's Chemical or Civil engineering stuff. Same principles apply as in EE, but different parts & pieces. A lot of those problems are solved via electrical analogs -- I've just got to do the reverse. Or, I could just throttle Valve A until the flows through both arms of the loop are identical and note the position of the valve for service use. Interesting problem.
    Last edited by Mikey; 07-02-2013 at 10:01 AM.

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