You need to test their strengths before you start because they could be degraded. I just tested some brand new bleach and it was around half the strength on the label. I know a lot of sterile growers use powdered pool shock but I don't know if that degrades over time. Bleach definitely does. I havent used UC Roots or Clear Rez but those products are essentially diluted bleach with huge markups. Your ppms could be way off if you don't test it first. So here's how to test your bleach without buying a $100 testing kit.
Take an empty drinking water bottle (500ml) and fill it with 0ppm distilled or RODI water. Make sure it tests 0 on your TDS meter. Then add 1 drop of your bleach to that with a dropper. Swirl or stir and wait a minute or 2. Since 1 drop = .05 ml, (Google it) if you do that math, you have just diluted the drop of bleach by a factor of 10,000.
Now test this water with your TDS meter. Whatever ppm reading you get, that's the percentage strength of the bleach. It's that simple. Let's say it tests at 4ppm like mine did. Your bleach is 4%, not 7.5% like it said on the label. (Optionally test it a 2nd way if you can- with a pool kit's strips or drops. TDS meters aren't always accurate either. If you get the same number, then you know it's correct.)
The reason this works is because the difference between percentage (1 in 100) and ppm (1 in 1,000,000) is a factor of 10,000, which is the same factor you diluted the bleach by. For example, since you diluted the bleach by a factor of 10,000, you now have to multiply the result of 4ppm x 10,000 to get the undiluted strength of the bleach and you get 40,000 ppm. To convert this to a percentage, divide that by 10,000 and you get 4.
Once you know the strength of your bleach, you can accurately calculate how much to add in order to get the ppm you need. The formula for that is X = (VP)/B, where V is the water volume in ml, P is your desired ppm of the resulting mixture, and B is the bleach strength in ppm. You are looking for X, the amount of bleach you need to add (in ml)
For example, if you have 1 gallon of 0ppm water and you want to add 2ppm of chlorine to keep away algae and root rot, you would first convert 1 gallon to 3785 ml, then you have 3785*2/40,000 = 0.189ml. Or roughly 4 drops of your 4% bleach.
Take an empty drinking water bottle (500ml) and fill it with 0ppm distilled or RODI water. Make sure it tests 0 on your TDS meter. Then add 1 drop of your bleach to that with a dropper. Swirl or stir and wait a minute or 2. Since 1 drop = .05 ml, (Google it) if you do that math, you have just diluted the drop of bleach by a factor of 10,000.
Now test this water with your TDS meter. Whatever ppm reading you get, that's the percentage strength of the bleach. It's that simple. Let's say it tests at 4ppm like mine did. Your bleach is 4%, not 7.5% like it said on the label. (Optionally test it a 2nd way if you can- with a pool kit's strips or drops. TDS meters aren't always accurate either. If you get the same number, then you know it's correct.)
The reason this works is because the difference between percentage (1 in 100) and ppm (1 in 1,000,000) is a factor of 10,000, which is the same factor you diluted the bleach by. For example, since you diluted the bleach by a factor of 10,000, you now have to multiply the result of 4ppm x 10,000 to get the undiluted strength of the bleach and you get 40,000 ppm. To convert this to a percentage, divide that by 10,000 and you get 4.
Once you know the strength of your bleach, you can accurately calculate how much to add in order to get the ppm you need. The formula for that is X = (VP)/B, where V is the water volume in ml, P is your desired ppm of the resulting mixture, and B is the bleach strength in ppm. You are looking for X, the amount of bleach you need to add (in ml)
For example, if you have 1 gallon of 0ppm water and you want to add 2ppm of chlorine to keep away algae and root rot, you would first convert 1 gallon to 3785 ml, then you have 3785*2/40,000 = 0.189ml. Or roughly 4 drops of your 4% bleach.
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