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Auto water change

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I have recently decided I want to up my reefing game and implement an auto water change system.  My current routine isn't too bad:  I'm using pumps, siphons and valves to move water around.   I'm not carrying buckets and there is no heavy lifting but it's still a manual process in that I have to watch it and turns things on/off.  I'm sold on the benefits of automating this using smaller more frequent water changes:

  • I can perform the change in my sump without having to disturb the display
  • I don't have to worry as much about matching temp and alkalinity
  • It's obviously easier on me (as long as the system is robust)
  • It's not as inefficient as I thought and it's not a big deal to just change more water to compensate:  http://reefkeeping.com/issues/2005-10/rhf/index.php

I've done some research and there seems to be 2 primary strategies for doing this:

  1. Peristaltic pumps to add/remove water at the same time (continuous)
  2. Drain and replenish using traditional pumps and float switches.

Most seem to prefer option 1 using Neptune DOS pumps.  I don't think this option is a good fit for me because I don't want anything noisy and I don't want to pay $300.  I'm sure it's much easier to setup though so maybe I'll try it one day. 

That leaves option 2.  I am a skilled programmer and I already have an apex and some traditional pumps laying around so it won't cost much.  Just need to figure out how to securely mount everything in the sump.  People warn that it could potentially result in disaster and won't be as accurate (salinity will drift) but I don't necessarily agree with that.  Float switches and float valves almost never fail in my experience (had a valve get clogged once, that's it) and I'm having a hard time foreseeing potential problems and issues that can't be addressed with redundancy.  I'll probably have a different attitude after I try it of course :)

Anyone doing this?  How's it working out for you?  Happy to share my progress if anyone is interested.

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If you use the the breakout box with the optical IR to kill the pumps on the apex to solve the overflow issue. vise versa use a float sensor in reverse extract the used saltwater when it closes it will kill the pump and the the second float to fill then tank back up from the new salt container, you can set the top float sensor on a delay in the apex, to insure you are not extracting the new water. take out from your overflow chamber in the sump and refill into the return section, watch how long it takes the first couple times, then set a feed mode to kill the skimmer and return pump if needed. I have put some thought into this, a few years ago after setting up the DIY ATO they used to sell backwards on the breakout box and watching the ATO not stop when the switch was closed.  the IR would just be insure the tank doesn't overflow. its possible to to this in reverse with an ATO like the Tunze 3155. I thought about the DOS but i just cant see that pump keeping up with refilling 20-30 gals in a timely manor.  

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17 hours ago, mhart032 said:

If you use the the breakout box with the optical IR to kill the pumps on the apex to solve the overflow issue. vise versa use a float sensor in reverse extract the used saltwater when it closes it will kill the pump and the the second float to fill then tank back up from the new salt container, you can set the top float sensor on a delay in the apex, to insure you are not extracting the new water. take out from your overflow chamber in the sump and refill into the return section, watch how long it takes the first couple times, then set a feed mode to kill the skimmer and return pump if needed. I have put some thought into this, a few years ago after setting up the DIY ATO they used to sell backwards on the breakout box and watching the ATO not stop when the switch was closed.  the IR would just be insure the tank doesn't overflow. its possible to to this in reverse with an ATO like the Tunze 3155. I thought about the DOS but i just cant see that pump keeping up with refilling 20-30 gals in a timely manor.  

I forgot to mention I also have a breakout box already.  My plan lines up almost exactly with your suggestions so that's validation I'm on the right track.  Thanks for the reply!

I already have high and low sensors in the sump and will repurpose  those for this application.  I have another sensor that's tied directly to my return pump (separate from my Apex) that kills the pump if the level gets too low.  Not going to touch that.  My plan is to have triple redundancy in both directions, drain and refill.  For the drain there will be the primary level sensor, a backup sensor just below that, and then the drain pump will be mounted just below that.  Worst case the cheap drain pump is damaged from running dry and I'm out $20.  For the refill, I will also have 2 sensors (primary and backup) and a float valve.  

I'm going to do exactly what you suggest by timing how long it takes to drain the desired amount and then set the drain cycle to be a little bit longer than that.  Same for refill.  Drain and refill cycles will be sequential and won't overlap.  One thing I haven't figure out yet from a coding perspective is how to send an alert if a water change isn't executed properly.  I'm sure I can find a solution but I know I'll end up babysitting it for the first month anyways which should give me some confidence.

Is there a reason you suggest optical sensors?  I've never used them before.  I don't have a specific reason for not using them, the mechanical sensors have always worked great.

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