Water change system & top off?

[Twizted1]

Ok it I am going to start ordering the stuff I need to change a large closet into a mini fish room. I just need a little guidence to what I may need or need to avoid. I need a mixing tank, fresh water top off tank, pumps ect. I would like to make it so I could hook up a pump to push the mixed & fresh to the tank. It is about 15' with very little head, maybe 2' on one end. I would like a full proof top off system with full proof back ups to avoid any messes.
 
So what kind of pump(s) would be best. I'm thinking 1 for fresh top off & 1 for the mixed. Total of 2 pumps.
Any worry about left over water in the lines?
I am going to have the RO-DI unit filling my fresh water tub. How do I set that up to fill it as it is being used so I don't have to watch it? I don't want it to overflo.
What size tubing will be best for all this? Would Plex work?
I am sure there are going to be more questions. I just want to get a list going. I am going to try & get the RO/DI unit, inline TDS meter and the sink thats going to go in there this coming week. I plan on getting it from Buckeye Feild Supplies. Any suggestions on that?
Sorry I am all over the place I have a problem staying on (look a clown fish) track. But I need to keep this going. Wish I would have had know this before I set my tank up. But, we all think that @ some point I think.
Thanks in advance for any and all help.

[charlieweaver]

Well for your fresh water supply from the rodi unit its just a simple float valuve. Like 8$ from buckeye field supply.

and if you have one of the auto shut of unit on your rodi it will detect the build up of pressure and turn your waste water off too.
. Its that white block on the unit. Only about 10$ and easy to install. From same company.

Pumps I use for water change were only like 20 bucks they are quite one 800. They do like 200gph and are adjustable too. They can do 5 feet head. Also pretty small too. 



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[charlieweaver]

For for the tubing from rodi just use standard 1/4 tubing that's on the rodi. And for the tube to the tank for the fresh and salt water I would just use 1/2in vinyl or even pvc would work I think pvc may be better light does not get through and allow algae to build in then when there is stagnant water.   Think that should all get you a good start.

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[charlieweaver]

One more thing I forgot. You could split your clean water from you rodi and run a light straight to your tanks or tanks if you split more. Would allow for a slower topoff. And allowing a slower change in temp or salinity.

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[ohioreef]

Google and read up on "TDS creep." It's better to have your RODI unit produce a large amount of water at a time rather than a little bit here and there.

[mrfish183]

It sounds like you are wanting to change water manually but have pumps do all the work.  I considered such an approach but eventually went with a continuous water change.  It costs a little more upfront but I'm glad I made the investment.  I also spent a little more money to get an accurate top-off system.  Here is what I have:

For the fresh water, I have an RO/DI unit feeding a 50 gallon Rubbermaid commercial trash can.  I have a cheap float valve in the trash can to ultimately stop flow.  The feed water to the RO/DI is connected to a solenoid valve and the valve connected to a timer.  I know approximately how much water my tank consumes and the production rate of my RO/DI throughout the year.  Based upon this knowledge, I set the timer sufficient to fill the tank twice per week with a couple hours extra.  This minimizes the "TDS" creep mentioned above.  I only have to change my DI once every ~3 months so I know my approach is working.  I have thought about switching to a high/low float switch system using my Apex, but the current system is working well. 

For top-off, I use a Litermeter III with level controller to fill my sump continuously.  The Litermeter is set to deliver slightly more water than the tank looses in a single day.  The Litermeter delivers the desired amount over many intervals.  Because the LMIII is set to delivery slightly more than the tank looses, the shut-off controller activates about once every couple days for a few hours.  Once the level goes back down, the process starts again.  Even if the LMIII level switch failed, there wouldn't be a problem because the LM is set to deliver only slightly more than the tank looses.  It would take several weeks for this event to cause an issue.  Plus, I have a second high level switch controlled through my Apex that shuts everything off if the level gets too high.   

For water change, I have the RO/DI hooked up to a large 100 gallon Rubbermaid container with a cheap float switch.  I have a MaxiJet powerhead in the container for water movement.  Once per month, I allow the RO/DI to fill the container.  I then mix the salt.  Once the salt is ready, two LMIIIs complete the continuous water change.  The LMIIIs change ~4 gallons per day of water for my 180 gallon system.  The sump contains both high and low level switches that shut-off all my LMIIIs if problems are noticed.  I monitor salinity weekly to ensure there isn't a mismatch in pump rate. 

Overall, the system above has worked well.  The LMIIIIs have to be calibrated occasionally plus they are a little pricey up-front.  However, LMIIIs can pump against almost unlimited head or "pull against" ~20' of head so they can be placed almost anywhere.  They only use 1/4" tubing so this can be hid almost anywhere. 

Another nice thing with this system is the waste water coming from my tank's continuous water change is delivered to a cascading series of quarantine tanks.  I never have to worry about having a quarantine tank ready . 

Good luck.