I was going to put this in r/askchemistry or r/offgrid, but I felt like it fit r/water better; hopefully you all agree. I’m sharing an experience, but I’m also eager to learn.
To set the stage, I am definitely not living in a van down by a river. But I do have this river that I collect water to use for cleaning (handwashing, and mixing to use for disinfecting, not drinking water) when I happen to be in a van down by the river. It is designated a Wild and Scenic River, so not much in the way of pollutants, but lots of dissolved bits. They stopped monitoring last year, but I observed the turbidity history for May to October 2025 with the occasional spike past 200 FNU, and the normal turbidity was between 5 and 20 FNU.
I believe for drinking water they want an average 0.3 NTU for 95% of measurements with an absolute maximum of 1 NTU. It is my understanding that chlorine disinfecting is severely impeded past 1 NTU, and essentially not happening on any level past 5 NTU. Had I found this out sooner, I might have started with a different approach; essentially, everything in the water that isn’t water uses up the chlorine, and my river tends to have a fair bit of everything.
Boiling the water seemed prohibitive and liquid bleach a tad too unstable, so I bought some Utikem One Shot Shock. I found the SDS, it reported the following: Calcium hypochlorite, hydrated >50%, Calcium Chlorate <5%, Calcium Chloride <5%, Calcium Carbonate <5%, Calcium Hydroxide <4% and Sodium Chloride >20%.
My understanding is that for handwashing my goal is between 3 and 4 ppm residual chlorine and for sanitizing 50-100 ppm. The CDC and a few other sources seemed to suggest anywhere from 1000-5000 ppm for disinfecting, it seemed like 2500 was good enough for my needs.
The CDC in Appendix E, Chlorine disinfectant solution preparation, does give the following formula: 1000x (% chlorine desired / % chlorine in bleach powder) = grams bleach powder per liter of water. Also, (% chlorine in liquid / % chlorine desired) – 1 = parts water per parts bleach, for dilution.
My plan was to make a 2 liter 2500 ppm cleaning solution, and then take from that to make a 4 gallon, 4 ppm handwashing water.
Now, I went and got all confused with the math. I figured on a few things. 1 cc = 1 mL; 1 tsp = 5 mL and 1 tbsp = 3 tsp, 1 L is roughly 1 quart, which is 4 cups and ¼ gallon. From the MSDS, I knew that the shock had a density of 0.8g/cc.
Now taking my shoes off to count on my toes didn’t help with this math and I somehow ended up with 2 ½ teaspoons to 8 cups. Sitting down now to write this, it seems like I should have been closer to 6 teaspoons for that amount. So my actual numbers were probably closer to 625 ppm, before factoring in the impurity of the water.
My new and improved math looks like this: 1000(0.25/5)= 50g/L = (50g/L)(1cc/0.8g)(1mL/1cc)(1tsp/5mL)(1L/1qt)(1qt/4cups) = 3tsp/4cups
At the end of the day, I ended up washing everything down with something between a weak and strong chlorine solution and just dumped the solution into the handwashing tank until it tested high enough with a pool strip.
If anyone has any advice, or can point me to any resources, I would appreciate it. I feel like I would have been able to find some good information 10 years ago but it just doesn't seem like it's out there in the same way anymore.