Chlorine bleach is an inexpensive and widely used chemical for sanitizing and disinfecting in restaurants, daycare and hospitals. The recommended concentrations for these can vary by as much as a factor of 50!. Unfortunately, the labels on off the shelf supermarket products are of little use when trying to dilute bleach correctly for most of these uses.
What Is ppm & Why Use It?
You encounter dilutions on a daily basis in many common things. Most liquors are 40% (80 proof) ethanol with the rest mainly water. 1 or 2% milk refers to the amount of fat with the rest being mainly water with some protein and sugar (lactose).
PPM (ppm) or parts per million is just another way to describe how much one thing (a gas, liquid or solid) is mixed in with another gas, liquid or solid. It is often used when one of these things is very much smaller than the other.
For example, 1 million parts per million is 100%. A penny is 1% of a dollar or 10000 ppm. A penny in $10,000 is 0.0001% and 1ppm, but 1 ppm is a bit easier to read & say.
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.
If we assume 5.25% and dilute according to the sanitizing work surfaces instructions, 1 tbsp in a gallon, we get about 200ppm. This is a common concentration especially in restaurants but is lower than what is used in daycare or hospitals.
Diluting Chlorine in American Units
You can work out any dilution with our Sanitizer Dilution Calculator but since it uses metric units, use these as a guide:
Now you try it. (steps 1,2,3,4 refer to where you enter numbers in the calculator) :
- Enter 5.25% for the concentration (step 1).
- Then 200ppm for step (2).
- Then 3800ml for step (3)
- 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 backwards. 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 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 Sanitizer Dilution Calculator:
- 1.5.25% for step (1)
- 1000ppm for step (2)
- 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 goes 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?
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:
- 5.25% for step (1)
- 200ppm for step (2)
- 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 acceptable.
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 the high side. A bleach solution that is a little low will still work it will just be a little slower killing germs. Besides, that is why there are test strips to help make sure you do it right.
- Different bleach test strips: 200ppm; 1000ppm; 2000ppm; 10000ppm
- Find out more about Color Vision & what we can see?
- 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.
Test strips 200ppm is common in restaurants. Cruise ships and senior’s homes often use 1000ppm levels. Some daycare centers prefer the 2000ppm test strips which can indicate have with intermediate levels such as 500 & 800ppm. Health care facilities such as hospitals are the main users of the 10000ppm test strips.
If you aren’t sure what you need, contact your local health authority. If you need assistance buying strips, give us a ring at (877)746-4764 betwen 8:30-5:00 Eastern Time, M-F.