Water · Water Testing
A 5-second dip that tells you whether your stored or treated water still has active disinfectant. Small, cheap, and genuinely useful at rotation time.
The basics
Chlorine residual test strips measure the amount of free chlorine remaining in water. For stored water treated with bleach, Water Preserver Concentrate, or any chlorine-based treatment, the strip confirms that the disinfectant is still active. If the residual has dropped below effective levels, microbes can regrow in a sealed container — even one that was properly treated at fill time.
The target range for drinking water chlorine residual is 2 to 4 ppm. Municipal water is typically maintained at 0.2 to 0.5 ppm at the tap; your stored water, treated at a higher initial concentration, should hold higher residuals for years when properly sealed. A result below 0.5 ppm in a container you treated with bleach months ago means the chlorine has degraded and you should re-treat before consumption.
Use strips at two points: when you fill and seal containers (confirm the initial treatment concentration is within range), and when you open stored water at rotation time or during an emergency (confirm residual chlorine is still present before drinking). A 5-second strip dip and 10-second color comparison is all it takes.
Below 0.5 ppm: disinfection residual is effectively gone. Re-treat with bleach (2 drops of 6% bleach per liter) or a fresh dose of storage drops, wait 30 minutes, and retest before drinking. Between 0.5 and 2 ppm: marginal; consider a small re-treatment dose if the container has been open or in questionable conditions. Between 2 and 4 ppm: ideal — drink. Above 4 ppm: safe but strongly chlorinated; aerate by pouring between containers or let sit uncovered for a few minutes. Above 8 ppm: do not drink without aerating.
Pool and spa test strips (any brand with a free chlorine pad) work for this purpose. They typically read in 1 to 5 ppm increments, which is adequate for rotation verification. For finer resolution, LaMotte or Hach drinking water strips read at 0.5 ppm increments. Either is sufficient. Stock 50 strips — a single pack covers years of testing at the cadence most households use.
Strips are reactive to humidity and light. Keep them in the original capped tube with the desiccant packet. Most strips are rated for 2 to 3 years. An expired strip may give a falsely low reading — replace on schedule when rotating other consumables.
Where to buy
Pool test strips with a free chlorine pad are available at hardware stores, pool supply shops, and Amazon for under $15 per 50-count. If you want finer resolution for the 0–4 ppm drinking water range, LaMotte or Hach strips are the standard.
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