Dosing kalkwasser from a large container (30-44 gallon Rubbermaid trash can)

kdx7214 · Nov 5, 2023

I've got a large Rubbermaid trash can that I use for RO/DI water for ATO. I use a peristaltic pump controlled by reef-pi (thanks RoboTank!) to control it. I'm looking into using kalkwasser for the first time and am trying to figure out if I can use it with this setup.

Right now my process is to let the ATO system do it's thing and periodically I check to see if the trash can is low and turn on the RO/DI. If I put kalk in the trash can and then it comes time to refill the water, how do I know how much to add? The RO/DI line runs directly into the can, so I have no idea how much water goes into the can.

How should I go about doing this so I don't muck things up?

QuickrdenU · Nov 5, 2023

I use a 44 gallon and it’s 180 grams for maximum saturation if my math was correct. Seems to be. Fill to the top of the handles on the inside. I would just wait until it’s close to empty, add water and only put 160grams in if there is roughly 5 gallons left. But you’ll probably want to give the kalk some time to settle before using. Like a day. So maybe auto top off by hand that day. Or buy 2 containers and swap them out.

kdx7214 · Nov 5, 2023

QuickrdenU said:
I use a 44 gallon and it’s 180 grams for maximum saturation if my math was correct. Seems to be. Fill to the top of the handles on the inside. I would just wait until it’s close to empty, add water and only put 160grams in if there is roughly 5 gallons left. But you’ll probably want to give the kalk some time to settle before using. Like a day. So maybe auto top off by hand that day. Or buy 2 containers and swap them out.

If I get too much and it settles and then I add water again later, will some of the excess dissolve as well or will it just be wasted?

Randy Holmes-Farley · Nov 5, 2023

I used 3 x 44 gallon Brute cans plumbed together, and used conductivity to gauge potency. There’s nothing wrong with excess on the bottom. It will just wait until refill.

kdx7214 · Nov 5, 2023

Randy Holmes-Farley said:
I used 3 x 44 gallon Brute cans plumbed together, and used conductivity to gauge potency. There’s nothing wrong with excess on the bottom. It will just wait until refill.

This will work then. My TDS meter also has conductivity included (I use it to for testing hydroponic tomatoes and peppers I grow over winter). What conductivity should it read for the correct potency?

Randy Holmes-Farley · Nov 5, 2023

kdx7214 said:
This will work then. My TDS meter also has conductivity included (I use it to for testing hydroponic tomatoes and peppers I grow over winter). What conductivity should it read for the correct potency?

10.3 mS/cm is about saturation at 25 C. You should put the probe in saturated kalk (say, 2 tsp calcium hydroxide in a cup of ro/di) to see what it reads. Some don’t have the right range.

kdx7214 · Nov 5, 2023

Randy Holmes-Farley said:
10.3 mS/cm is about saturation at 25 C. You should put the probe in saturated kalk (say, 2 tsp calcium hydroxide in a cup of ro/di) to see what it reads. Some don’t have the right range.

Thanks, I'll go set that up at soon as I get some Mrs. Wages.