Chlorine (Sodium Hypochlorite)

Chlorine bleach is a common sanitizer/disinfectant used at home, in restaurants, childcare centers and hospitals. Figuring out the right dilution for small amounts in spray bottles or larger amounts for sinks & buckets can be a challenge. We explain how so you make the best use of your Indigo™ sanitizer test strips.

What is ppm & Why Use It?

You encounter dilutions/concentrations on a daily basis in many common things. Most liquors are 40% (80 proof) ethanol (ethyl alcohol) with the other 60% being mainly water. The 2% in milk refers to the amount of fat with the rest mainly water, and a bit of protein and sugar (lactose).

PPM(ppm) and percentage are related. 1,000,000 parts per million (1000000ppm) is 100%. PPM is often used when very small amounts of one thing are dissolved in a large amount of something else, usually water.

Consider money. One cent is 1% or 1/100th of a dollar which works out to 10000ppm. If you had $10,000, 1 cent would be 0.0001% (a millionth) or 1ppm. You never see money described this way but reading a bunch of reading zeroes after a decimal can be confusing. Which do you find easier to read?

You may also encounter mg/L which is the weight of something dissolved in a liquid (usually water). 1mg in 1L is equal to 1ppm but you may want to brush up on your metric first!

Chlorine bleach test strips

Chlorine test strips cover a variety of ranges. The leftmost is for residual levels of 0-10ppm. In front are  200ppm restaurant strips and behind them the very high-level 10000ppm. To the right are the 2000ppm which are popular in childcare centres.

Chlorine Bleach Labels-USA

Below is a label from a typical brand of chlorine bleach. The dilution instructions are relatively easy to follow but the bleach strength isn’t indicated anywhere so you can’t tell what ppm you get even if you follow the instructions perfectly.

Most store-bought bleach in North America is 5.25% so if you dilute according to the instructions, 1 tbsp in a gallon, you’ll end up with about 200ppm. Be sure to check the label though. Store-bought can be less than what is supplied to daycare or hospitals & can be as high as 8%.

US Chlorine Bleach Label

Information for meeting the sanitizing & disinfecting regulations used in different cities, counties & states is missing from this label.

Diluting Chlorine in American Units

You can work out any dilution with our Dilution Calculator but since it uses metric units, use these as a guide:

1 tsp=5ml
1 tbsp=15ml
1 cup=~235ml (or round to 250ml)
1 quart=~950ml (or round to 1000ml/1L)
1 Gallon=~3800ml (or round to 4000ml/4L)

Now you try it.  (steps 1,2,3,4 refer to where you enter numbers in the calculator) :

  1. Enter 5.25% for the concentration (step 1).
  2. Then 200ppm for step (2).
  3. Then 3800ml for step (3)
  4. Press Calculate.

You’ll see a result in the box for step (4) that says 14.48ml which is very close to 1 tbsp.

You can work backward. Clear the 200ppm from step (2), enter 15ml in step (4) & press Calculate. You’ll see 207ppm appear in the box for step (2). This is close to 200ppm.

The label instructions for disinfection call for 3/4 cup in 1 gallon. If you work this out in the Dilution Calculator, you get about 2500ppm.  Since many state regulations call for only 500, 800, 1000, or 2000ppm, you end up using far more bleach than you need. 1

If all you need is a spray bottle to sanitize faucets, handrails, or countertops, a gallon is too much.  To make up a quart  diluted to 1000ppm,  just enter the following steps in the  Dilution Calculator:

  1. 5.25% for step (1)
  2. 1000ppm for step (2)
  3. 950ml for step (3)

Pressing Calculate gets a result of 18.1ml which you can round up to 20ml or 4tsp.

Chlorine Bleach Labels-Canada

The Canadian label has instructions in metric units that are of little use.  Dual-unit measuring cups have metric units on one side. The markings go to 125ml & 250ml, not 120 & 240ml. Larger 4-cup versions have metric markings at 500 and 1000ml (1 litre) not 475 & 950ml.  What to do?

Canadian Chlorine Bleach Label

These instructions say 120 & 240 ml instead of 125 & 250ml which are the actual graduations on the metric side of a measuring cup.

Since percentage and ppm are based on units of 10, preparing a 1 litre (1000ml) spray bottle for 200ppm is simple. Just enter the following in the Sanitizer Dilution Calculator:

  1. 5.25% for step (1)
  2. 200ppm for step (2)
  3. 1000ml for step (3)

Press Calculate and you get 18.1ml which rounds up to 20ml or 4tsp.  This works out to about 1100ppm which is within acceptable limits.

What PPM is Too High or Too Low?

The human eye can detect over 10 million colors but subtle shade differences are still hard to see.2  Our eyes evolved to see color using natural sunlight but indoor lighting such as fluorescent, halogen or LED can make things look more yellow or blue or somewhere in between.3  As long as the color chart matches what you want pretty closely, you’re ok.

Your health inspector likely prefers a dilution on the high side. A bleach solution that is a little low will still work but will take a little longer to kill germs. Test strips let you know you are within the right range.

What About Hydrogen Peroxide?

The dilution calculator works with any concentration of hydrogen peroxide. Pharmacies usually supply it in small bottles at 3% concentration. Higher concentration “food grade” is sold in larger volumes for use in hot tubs, pools, float tanks, etc. This is usually supplied as 35% but we have seen lower amounts; check the label.

What About Quats (QAC)?

Quat formulations differ depending on the manufacturer. The simple answer is to consider them to be 100% & dilute accordingly. If in doubt, ask your sales representative what their company recommends.

Which Chlorine Test Strips to Use?

Test strips of 0-200ppm are commonly used in restaurant kitchens. (see our blog: Wash/Rinse/Sanitize). Cruise ships and senior’s homes often use 1000ppm levels. Some daycare centers prefer our 2000ppm test strips which indicate sanitize & disinfect levels of 500 & 800ppm.  Healthcare facilities such as hospitals are the main users of the 10000ppm test strips since these allow for chlorine uptake by organics such as blood.

If you aren’t sure what you need, contact your local health authority. If you need assistance buying strips, give us a call at (877)746-4764 between 8:30-4:30 Eastern Time, M-F.

References & Related Information

    1. Different bleach test strips: 200ppm; 1000ppm; 2000ppm; 10000ppm
    2. Find out more about Color Vision & what we can see?
    3. Light and how it affects the colors we see is a complex topic. It is best to start with understanding Full Spectrum Light, i.e. sunlight.
    4. What Kills Norovirus on Surfaces? Chlorine bleach works fine on any hard surface from dishes to doorknobs.
    5. Test Strip Expiration Dates; Good Today, Dead Tomorrow? Don’t toss good test strips away. Good today doesn’t mean bad tomorrow.
    6. Wash, Rinse, Sanitize: The Three Sink Method. A simple technique for kitchens anywhere.
    7. Chlorine Bleach Disinfectant-An Old Chemical for New Bugs. Frequent cleaning doesn’t have to be expensive.
    8. Chlorine Test Strips-Daycare Disinfection Checklist. Common & not so obvious things to disinfect not only in daycare but office, business or home.
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