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Plumbing a sump for auto water changes

Discussion in 'General Plant Topics' started by midazolam, Aug 24, 2008.

  1. midazolam

    midazolam Junior Poster

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    In designing and planning for my purchase of a large tank I've decided it is essential, given my erratic work schedule, that water changes be automated. I would prefer something like 10% a night for a total of 70% a week. This keeps the volume of waste water low on a per day basis (which I will use to irrigate my yard) and the replacement volume low so that in the winter it wont be as much of a temperature burden.

    My question is, what is the most reliable way to do this.

    Here's what I'm thinking.

    First, will use a controller, probably an ACIII.

    Will have a float switch in the tank to keep it topped off. Will be hooked up to the fill solenoid. This will always be on except for during the water change.

    Will have another float switch mounted upside down in the sump at the level of a 10% change that the ACIII will keep off until the schedule water change time. This float switch will control a solenoid that opens the drain. I'm not sure if I could use my return pump to pump water out or if I would need a dedicated pump?

    So basically it would go like this.

    4 AM. ACIII deactivates top off float switch and activates drain float switch. Water is pumped into drip irrigation system outside until upside down (drain float switch) reaches 10% level. Then, I would have the ACIII turn the top off solenoid on. Maybe time it and have the ACIII keep the top off turned off for 10 minutes longer than it takes to drain the tank unless I can have the ACIII recognize when the drain float switch is done with its thing then turn on the other one. Never played with an ACIII so not sure what they are capable of.

    Sounds pretty easy so I figure there's something I'm not getting.
     
  2. VaughnH

    VaughnH Lifetime Charter Member
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    I'm very nervous about using switches of any kind, with electric valves of any kind, to operate an automatic water change system. Electric components have a nasty habit of failing. If a float switch doesn't shut off the inlet flow when it is supposed to, the extra water will just flood the floor - right? A flooded floor is one failure that is not tolerable for me.

    A much more "fail safe" arrangement would use an overflow to limit the quantity of water in any tank or sump, with a constantly open drain line to handle any over filling thru the overflow(s). I expect to move in a few months, and hope to set up a tank then, using a system of this type. My current system uses a tank overflow to prevent any over filling of the tank, with a constantly open drain line. I keep a dripping flow of refill water going into the tank 24 hours a day, giving me about 5-10 gallons of change water per day for a 45 gallon tank. But, to do this I had to drill a big hole in the wall of my condo.
     
  3. midazolam

    midazolam Junior Poster

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    AFter looking at your DIY thread where you built that crazy flow reverser thing I was a little worried when I saw you responded; however, your suggestions sounds quite reasonable and easy to do. I would have to just waste the water vs. using for irrigation (or store it some how) but I guess I could live with that. Plus your way I wouldn't have to put holes through any walls leading to the outside.
     
  4. Tom Barr

    Tom Barr Founder
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    BTW, if you change 10% a day, it's not the same as 70% total for the week as far as nutrient or build up ppm's.

    This is because you are remixing the total other 90% and removing a little bit of the 10% each time you just changed.

    See "infinite series" in chemical dilutions.
    It's actually covered a long time ago in PMDD, and is the basis for EI's use of water changes and build up(I did not come up with it -never claimed too either):

    See the very end:

    Practical PMDD Information

    Regards,
    Tom Barr
     
  5. Tom Barr

    Tom Barr Founder
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    The sump water changer will work well using a solenoid, say a small 1/4, 3/8" size drain solenoid and place it on a timer.

    then you simply add a float switch in the sump, this is also good for automatic top off for evaporation loss(not bad when you leave for a few days etc).

    Float valves work pretty well.

    You need to make sure that the system is rather slow, if it's going to be automated, so a small hose and slow drain and refill is best.

    If you want semi automation, then, you can go 1" to 2" size PVC hard plumbed drain and fill valves that you can turn yourself, this will take maybe 5-10 minutes to drain and maybe 30-60 min to refill without touching a bucket or a hose, then you can trim and work on the tank as it refills.

    Those are a couple of choices.

    I prefer the large semi automated, as with any large tank, access and being able to get at the tank, reworking it etc if there's an issue, blindful neglect and ignoring it, will never make up using small automated changes.

    Then when you need to do a large change, and unless you set up both plumbing methods, you can cause yourself a lot more headache.

    Just be careful in how you assume how great such systems are, they both have strong benefits. You really cannot do the larger change automatically without a lot more risk involved. And can you accept water all over your home?
    I have some well heeled clients and that's not an option.

    So they can hire someone etc to tend the tank if they are not around.
    Po folks can ask their friends etc.

    Regards,
    Tom Barr
     
  6. midazolam

    midazolam Junior Poster

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    Hmm, sounds like plumbing multiple is the way to go. Float for top off. Can do small nightly changes and once a week if out of town or maybe just "because". Plumb a larger drain/fill for manual weekly 50%'ers. Maybe use Vaughn's idea as a fail safe...put like a 1/2 bulkhead (actually, I guess as long as the bulkhead was bigger than the inflow I should be ok) at the bottom of a really tall overflow (one that would not overflow and normal operating height of the tank) so if one of the above methods fails at least SOME of the water will end up down the drain and not on the floor.
     
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