How Much Chlorine Bleach To Add In My Water Storage – When Is It Enough?

water storage bleach

If you are storing water in containers, 55 gallon drums, or any bulk size tank as a reserve for “just in case”, how much chlorine bleach (if any) should you add?

This has been a common question and I’ve written about it a number of times over the years. I really haven’t changed my opinion about it, however it has been awhile since I brought up the topic. So here we go…



Do I Need To Add Bleach To My Water Storage?

It certainly won’t hurt and it will likely help if you add the right amount of bleach to your long term water storage containment.

If you are sourcing your water from your home’s municipal water supply, the water will already be treated to an extent (a small extent).

If your long term water storage is from your well, there will be nothing to inhibit organic contaminants (if there are any), so it may be a good idea to add some chlorine bleach.

Certainly if sourced from a pond or stream you should treat the water to eliminate organic contamination.


How Much Regular Bleach To Add?

In a previous article, “Bleach – Water Ratio For Drinking Water” I listed the appropriate amount of bleach to add versus how many gallons of water being stored.

(Read on for the amounts…)

This would amount to enough chlorine to eliminate organic contamination from the water while keeping the overall level less than 4ppm (parts per million), the maximum cutoff for drinking water according to the EPA. Actually the amounts listed will result in approximately 1ppm depending on your water.

Note: Important – Use “Regular” bleach (no additives, scents, etc..)
Note: Numbers are ’rounded’ (don’t worry there is a very wide margin)
Note: tsp = teaspoon

Regular Bleach containing 8.25% Sodium Hypochlorite

1 Quart water, 1 drop bleach
1 Gallon water, 5 drops bleach
5 Gallons water, 3/8 tsp bleach
10 Gallons water, 3/4 tsp bleach
50 Gallons water, 3.5 tsp bleach

Regular Bleach containing 5 – 6% Sodium Hypochlorite

1 Quart water, 2 drops bleach
1 Gallon water, 8 drops bleach
5 Gallons water, 1/2 tsp bleach
10 Gallons water, 1 tsp bleach
50 Gallons water, 5 tsp bleach


How Do I Know When I’ve Added Enough Bleach?

The rule of thumb is this… If you can detect a hint of chlorine smell in the water, it’s enough.

Better yet, use an ordinary swimming pool chlorine test kit to measure the amount of chlorine in the water.

0.5 ppm – 2 ppm is a range that may be appropriate. Your municipal water supply likely measures between 0.5 and 1.0 ppm.

I recommend the following Taylor test kit:

Taylor K-1000


Will I Need To Add More Bleach Later?

Bleach will break down after awhile. It actually reduces to salt.

I have read (I believe it was from Clorox) that the potency of regular chlorine bleach will diminish to approximately half strength after ~ 1 year.

That said, if your treated water is sealed up in a container and stored properly, there should be no “new” contamination, even after a period of time.

What is “stored properly”?

– Closed up so nothing can get in
– Out of direct sunlight / excessive heat
– Preferably in a relatively cool place

Since chlorine does break down, it wouldn’t hurt to add more if you felt like doing that.

What I generally do is drain and replenish my water storage once a year. When it’s replenished I add chlorine bleach and it’s good to go for another year.

Why do I change my water storage every year?

Although it’s not necessary, because water is water is water, it simply puts my eyeballs on it for ‘just in case’ something went wrong. It makes me feel better…

More: Is Stored Water Safe After One Year?

More: Water Sources and Treatment

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