Chapter 06
Water that you can drink
Boil if you can. Dose if you must. Filter first either way.
Dirty water is a particle problem and a germ problem. Chemistry that kills germs does a worse job when dirt is still in the glass. Settle, strain, then disinfect. The Field Tools page will do the drop-count for you. This chapter is the why.
Order of operations
- ▸Source the cleanest water you can (closed well, rain from a clean roof, a known spring) before you reach for ditch water.
- ▸Let mud drop. A pinch of bentonite or even time in a still bucket helps. Decant the top.
- ▸Strain through cloth or a coffee filter.
- ▸Boil, or dose with unscented bleach per the EPA table, or dose from a calcium hypochlorite stock per EPA, or use a rated filter that actually claims bacteria and protozoa — then still consider a chemical residual if the water will sit.
- ▸Wait the full contact time. Thirty minutes is not a suggestion.
EPA bleach table (unscented household)
Clear water. Double the dose if cloudy, colored, or very cold. Wait 30 minutes.
| Volume | 6% bleach | 8.25% bleach |
|---|---|---|
| 1 quart / liter | 2 drops | 2 drops |
| 1 gallon | 8 drops | 6 drops |
| 2 gallons | 16 drops (¼ tsp) | 12 drops |
| 4 gallons | ⅓ tsp | ¼ tsp |
| 8 gallons | ⅔ tsp | ½ tsp |
After 30 minutes you want a faint chlorine smell. No smell: repeat the dose, wait 15 more minutes. Still nothing: the bleach is likely spent. Boil, or open a newer bottle. A pinch of ascorbic acid after the wait will take the pool taste down — after, never before, or you spend the chlorine in the glass instead of on the germs.
When you have pool shock instead of bleach
Granular 65–73% calcium hypochlorite, no algaecide. Make a stock: 1 heaping teaspoon in 2 gallons of water. That stock is roughly 500 mg/L. Dose the water you will drink at 1 part stock to 100 parts water. Wait 30 minutes. Store the bag of granules like an oxidizer, alone, cool, dry.
Boiling still wins
A rolling boil. At or above about 6,500 feet, give it 3 minutes. The Mogollon Rim and Flagstaff are not Phoenix. Boiling does not remove most chemicals, and it does not leave a residual for the bottle on the shelf — drink or re-treat. It does kill the living things that make you sick this week.