Water · Water Treatment
The cheapest water disinfectant in your house, if you know the concentration. One gallon treats roughly 3,800 gallons of clear water — but only if you use it correctly.
The basics
Unscented household bleach is a sodium hypochlorite solution that kills bacteria and viruses in water. Most households already own it. It costs less than any other treatment option, stores for up to a year, and a single gallon can treat thousands of gallons of water at the correct dose.
In a preparedness context, bleach serves as a backup disinfection method when stored water runs low and you need to treat water from a tap under a boil-water advisory, a container that has been sitting, or a water source you're uncertain about. It works quickly and requires no equipment beyond a clean dropper or measuring spoon.
The catch is the concentration. Bleach sold in the U.S. comes in two common strengths: 6% sodium hypochlorite and 8.25% sodium hypochlorite (often marketed as "concentrated"). The number of drops needed is different for each, and using the wrong amount either leaves the water undertreated or makes it taste harsh. Before you use bleach to treat water, check the label.
Bleach also has real limits. It does not remove heavy metals, chemicals, or sediment. It does not kill Cryptosporidium. And once the bottle has been open or stored beyond a year, potency drops below reliable treatment levels. Understanding what bleach can and cannot do is as important as knowing the dose.
Quantity
One gallon of unscented household bleach per household is a practical baseline. A gallon treats roughly 3,800 gallons of clear water at the standard 6-drop-per-gallon dose — far more than any household will need in a typical disruption. The limiting factor is not quantity but freshness: bleach loses potency over time, so the rotation schedule matters more than the volume stocked.
Baseline stock: One gallon, unscented, 6% or 8.25% sodium hypochlorite. Rotate annually — write the purchase date on the bottle with a permanent marker. Keep it in the original opaque container in a cool, dark location. Do not transfer to clear containers or mix with other chemicals.
Storage
Sodium hypochlorite degrades over time even in a sealed container. At room temperature, bleach typically maintains effective concentration for 6 to 12 months from the manufacture date. Heat and light accelerate that degradation — a bottle stored in a hot garage loses potency much faster than one kept in a cool closet.
Store bleach in its original opaque container in a cool, dark location away from heat sources. Do not transfer it to a clear container. Do not store it near acids, ammonia, or other household cleaners — mixing bleach with these produces toxic gases.
The manufacture date is printed on most bottles (not the expiration date — look for a code on the bottom or label that indicates when it was made). If you cannot determine the manufacture date and the bottle has been open for more than a year, replace it. Expired bleach used to treat drinking water may not produce safe results.
Bleach does not become toxic when it expires — it simply stops being effective. The sodium hypochlorite breaks down into salt and water. If you use expired bleach and cannot smell any chlorine after the 30-minute wait time, you do not have treated water. Boiling is the fallback when bleach of uncertain age is all you have.
What to buy
Any store-brand unscented bleach works as well as Clorox for water treatment. The only things that matter are the active ingredient, the concentration, and what is not in the bottle. Check the label for all three before buying.
Use this
Unscented, plain
Active ingredient: sodium hypochlorite (6% or 8.25%). No added cleaners, no fragrance, no thickeners.
Not this
Scented or color-safe
Scented bleach, color-safe bleach, or bleach with added cleaners or thickeners. Do not use for water treatment.
Avoid
Ultra-concentrated (>8.25%)
Precise dosing at very high concentrations is difficult at home. Stick to 6% or 8.25% products.
NWS recommendation: Clorox Regular Unscented (8.25%) is widely available and well-labeled, which makes it easy to confirm you have the right product at the right concentration. Any store-brand equivalent with the same active ingredient works identically.
Safety and dosing
Use the table below to determine how much bleach to add based on your bleach concentration and water clarity. All figures per EPA guidance.
| Water volume | 6% bleach (clear) | 8.25% bleach (clear) | Cloudy water |
|---|---|---|---|
| 1 quart (1 liter) | 2 drops | 2 drops | Double the dose |
| 1 gallon | 8 drops | 6 drops | Double the dose |
| 5 gallons | 40 drops (~½ tsp) | 30 drops | Double the dose |
| 7 gallons (Aqua-Tainer) | 56 drops | 42 drops | Double the dose |
Dosing per EPA Emergency Disinfection of Drinking Water. Verified June 2026.
Where to buy
Unscented household bleach is available at every grocery store, hardware store, and big-box retailer. You do not need a specialty retailer. The main things to verify at the shelf: unscented, no added cleaners, and concentration listed on the label as 6% or 8.25% sodium hypochlorite.
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