Build a ph doser/controller - under $100 - tutorial

Ok, so what's a huge issue that we're always dealing with in hydro? Ph of course! Personally, I hate having to deal with it multiple times a day, but I can't afford to spend $1500 on a professional doser system. The following system is only an acid doser, however with some tinkering you could likely make it both acid and base capable, however I will not cover that. Making it function as an acid doser is a simple process that will be extremely easy for anyone.

Items needed:
1. Milwaukee SMS122 continous ph monitor/controller - $83 - You can get these off ebay, there's tons of them. Just be sure to get the correct model number, as you must have this one to perform the acid dosing. They do have ones that are only monitors, and that's obiously not what you want. Just match up the model number to be sure you're getting the right one.

2. Smallest submersible pump you can find - $10 - I found one at a hardware store for $10 and it's an extremely low flowrate, only 30 gph. Look for adjustable ones too, I should be able to adjust mine lower.

3. Acid Reservoir - $3 - I just bought a juice pitcher for a few bucks. Make sure that it's plastic, so that it will hold up to the acid just fine. Also, it's important to have a way for air to get in through the top, as it will be needed as you pump the acid out.

4. Appropriate tubing - $2 - you'll likely need 10 feet or less, unless you're in an abnormal situation. Bring your new pump with and just find the smallest tubing that your pump is capable of using. I used 1/4" inside diameter. Color makes no difference, as nothing will grow in the acid anyway.

TOTAL COST: $98

Let's get building!

Well, I guess I'd hardly call it building, but bear with me. This should only take you 20 minutes at the most once you have all your supplies. First, calibrate your new ph meter with two points using 7 and 4 ph buffer solutions. The centerpoint will be off most likely, but the slope will probably already be pretty close. The instructions with the monitor are pretty clear on this process.

So, start by hanging your monitor on the wall so you can easily keep an eye on it while it's running. First off, you'll notice what looks like a ac to dc adapter with a plug in it. This actually does not power the monitor, rather it's a switch that the unit controls. Look at the pictures to understand the setup, but basically when the ph rises above your setpoint, it will turn on this outlet. This is the key to the functioning of this system. Plug that in, and then find the ac-dc adapter for the unit. Attach the ph probe and your monitor should be completly setup! Now, we need to set up our dosing system.

The juice pitcher that you had should be filled with acid. I'm not sure yet what the best concentration is, perhaps we can report our findings as we test it out. But basically, the more concentrated it is, the longer it will be maintainance free. Now, plug your submersible pump into the switch that is controlled by the ph meter. Connect your tubing to the pump, and place it in your acid reservoir.

Now this next part may be key to prevent over dosing! I have used a cable tie to attach my acid tube right to my ph probe. It's up the probe housing from the sensor several centimeters, however by injecting the acid near the probe, it will cause pulses off acid instead of pumping large amounts as the ph fluctuates. Feel free to experiment, but just be careful of what could happen and keep a close eye on it until you're confident you can trust it.

So, go ahead and set your setpoint and sit back to watch your meter automatically dose! If you get more acid flow than you would like, choke back your pump or put a c-clamp on the tube to reduce flow.

I welcome input and discussion on this. I've got it setup, but I just finished a rebuild on my hydro system, so I've gotta wait for the sealants to dry before I can fully test it. I hope this helps alot of people! :D

more pictures