My Super Easy DIY Auto Water Change

[dread240]

So awhile back using the New Posts feature on reefcentral, I got sucked into the florida forums unknowingly and began working with a few other guys on getting a low cost, easy auto water change solution going.

 

We were buying used pharmaceutical and industrial peristaltic pumps and modifying them to convert to a dual head system, instead of spending the money on brand new stenner pumps or masterflex pumps.

 

I ended up buying 2 Thermo-Fisher units with cole palmer masterflex heads on them. These heads are nice because you can stack them, so I removed the head from the second unit, and using some 8-32 all thread, I was able to double up the heads on a single motor so that they stay in sync. If enough people are interested I'll try and find a good source for these again, but the prices have risen from some of these sellers considering between myself and the others on the forum we probably purchased 30-40 of these pumps from them. In total, I purchased...

 

12V-40V 10A Pulse Width Modulation PWM DC Motor Speed Controller ($6.99 Shipped from Ebay)
ThermoFisher D3138-13 w/Masterflex 7024-20 Pump (2 of them for $48.52 Shipped From Ebay)
5' of Laboratory Clear Tygon PVC Tubing, 1/4" ID, 7/16" OD, 3/32" Wall Thickness, 5' L ($19.32 Shipped from McMaster Carr)
12v 1A power supply I had sitting around the house, can be had for about 10 bucks though.

 

Pump supplies = $84.83 (I added in 10 bucks for a power supply which I already had)

 

My water change station I had already setup, but I did change it up slightly for this new setup to make my life easier, but the costs for that are

 

15g Barrels I had previously, got them off craigslist for like 15 or 20 bucks each.
Various PVC fittings, unions and yadda yadda to build water mixing station (70 bucks roughly)
Used Mag 7 laying around, but could probably pick one up for like 30-40 bucks or so

 

water change station cost = $150 if you had to do it all from scratch.

 

Now for the water change station

 

 

The 2 barrels are joined by PVC piping to allow one pump to handle the mixing, transfer, and circulation duties of the system. By opening and closing valves I can accomplish anything I need.

 

The barrel on the left is the starting barrel. RO/DI water comes into the top of this barrel with a float shutoff to stop it's filling. I mix the saltwater in here and once my salinity is correct, I close the top valve on the left, and open the top valve on the right. This transfers the water to my dispensing barrel on the right. I then close the bottom left valve from the mixing barrel and open the bottom right from the new saltwater barrel and this allows me to keep the new saltwater aerated and turning. During this time I generally turn my RO/DI system back on and fill up the fresh barrel. After a few days of running on the new saltwater barrel, I valve back over to the new freshwater and mix up another batch of salt, so it's ready before I run out of new saltwater. There is also a low level safety shutoff switch installed in the new saltwater barrel that is tied into my apex that turns off the pump should I run low on saltwater.

 

Seems like alot, but this literally takes 1 minute every week or so to mix up new salt and transfer it over. You also see a 1/2" push lock fitting behind a valve on the top of it. This is for manual water changes for siphoning detritus and the such. I also have valves on the old water drain so that I can capture old tank water while the pump is running if need be.

 

The pump that I got was originally designed to run at 200rpm, and was 12VDC supply. You definitely want a DC supply pump as it gives you complete control over how fast you want it to run (and believe me, these things make a racket at 200rpm). I have mine turned down to about 15rpm or so, and it's barely audible in the room. The video below has alot more noise going on because I made this video up tonight for some of the florida guys, and I have fish in QT, which I let the water evaporate to get the salinity up to the right level.

 

http://s770.photobucket.com/user/Dread240/media/VIDEO0033_zps5daf8dd9.mp4.html << link to video, don't know how to embed on here

 

There you can see just how slowly I can get this pump to run with the pwm motor control. It actually pulls so little power on this setup that it must be on a relay outlet on an apex (either outlet 4 or 8 on an eb8, or any outlet on an eb4).

 

Currently this is all controlled by an apex. Here's the programming for it from there....

 

Fallback OFF
OSC 000:00/010:00/050:00 Then ON
If Outlet AWC_Override = ON Then ON
If LowNSW CLOSED Then OFF

 

Fallback OFF is to make sure this never turns on if it loses communication with the base module

The oscillate command lets the pump run for 10 minutes every hour on the hour. Right now this is letting me change about 20% per week (roughly 14 gallons on a 75 gallon tank). I will be backing this back down to about 10% soon, but I'm letting it go crazy for the time being because I was really really behind on maintenance with the tank and this is letting the levels get back in line (I also had an ATO failure back in November and lost almost the entire tank, so nutrients skyrocketed but have came back down nicely, and is also the reason I own an apex now to avoid those problems)

The AWC_Override outlet is a virtual outlet created in the apex. This allows me to turn it on anytime I want, but still uses the main outlet in automatic so I can have the protection of the float switch. I have this because I have tee'd the drain line of the pump so that I can collect old tankwater for the QT tank and for doing tank transfers with buckets before new fish go in.

"If LowNSW" line is referencing the float switch in the barrel. This turns the system off if I'm low on new saltwater in the barrel so that the pump doesn't drain the tank and not refill it.

 

So far on this pump setup it's been going for a little over 4 months now. I do have to check salinity a bit more often, but I have yet to adjust for it. The tank stays rock solid 1.026. I have measured the output on both pumps and over the course of 30 minutes I had 1ml difference between the two (measured both out exactly). This is far superior to using 2 hobby grade pumps and trying to calibrate them like I had previously done, as with them being on a single motor they will always spin at exactly the same speed, and push the same amount of water.

 

The other benefit to using peristaltic pumps is their resistance to head pressure. We have people with their mixing stations in the basement and over 100 feet away of line, and they can maintain the same flow rates through both heads. I have yet to hear of a single complaint or problem of anybody running a setup like this.

 

Only caveat we did find out... which I didn't expect to be an issue as they are DC motors, is that almost every one of these pumps has an internal or external diode assembly to where polarity does indeed matter on them. You cannot reverse the polarity of the motor, they simply won't work and can damage the motor, so you have to have a little bit of know-how and a multi-meter to test for correct polarity when wiring it up. Other then that, it's incredibly simple.

Edited February 24, 2014 by dread240

[ctenophore]

Nice write up. Funny you mention how the cole parmer heads stay in sync for you. I had the exact same pump setup, but mine would be off by 15% despite identical tubing (diameter and length). The difference was due to the head pressure heights. Sump to drain was 8' up and over, but new saltwater to sump was 6' downhill. Now I use a pair of independent peri pumps that have stayed calibrated much closer, exactly the opposite as you describe.

[jason the filter freak]

Now if I only had the space...
p.s. great write up

Edited February 24, 2014 by jason the filter freak

[s2nhle]

Thank you for sharing. Where can I purchase the pumps?. How much will it be? I would like to set up an auto water change for my system. Thanks,