Today’s lecture is on the difference between understanding the reasons why authorities tell you to do certain things rather than simply being content with what they say. The authority in question for this particular lecture is the EPA and their instructions on how to use pool shock to disinfect water.
Now before we start I want to make it clear that I am not out to bash the EPA on this particular issue. I think it is a good thing that some bureaucrat took the time to go through all the steps and all the committees that it took to get this on a public facing federal website. It is true that it is poorly written but good writers are hard to come by and I imagine that what good ones the EPA had were needed for higher profile subjects. But fundamentally, I think it is a good thing that a federal agency is letting the world know that it is okay to treat drinking water with pool shock in the event of the emergency.
The problem that I have is that some (many?) people who are interested in preparedness are simply content to accept that “the EPA says it is okay” without understanding why the EPA says it is okay. I would think if you were interested in being prepared you would want to know why the EPA thinks it is okay and how it works rather than be simply content with “the government says so.”
So we what we are going to do is pick apart the EPA instructions to try to figure out “why” they say what they do. Our first step is to look at the EPA directions as they are retrieved on 7/17/2021 (they could change them and probably should make them a little clearer).
You can use granular calcium hypochlorite to disinfect water.
Add and dissolve one heaping teaspoon of high-test granular calcium hypochlorite (approximately ¼ ounce) for each two gallons of water, or 5 milliliters (approximately 7 grams) per 7.5 liters of water.
The mixture will produce a stock chlorine solution of approximately 500 milligrams per liter, since the calcium hypochlorite has available chlorine equal to 70 percent of its weight.
To disinfect water, add the chlorine solution in the ratio of one part of chlorine solution to each 100 parts of water to be treated. This is roughly equal to adding 1 pint (16 ounces) of stock chlorine to each 12.5 gallons of water or (approximately ½ liter to 50 liters of water) to be disinfected.
To remove any objectionable chlorine odor, aerate the disinfected water by pouring it back and forth from one clean container to another.
Now I personally did not find that too hard to understand, but I am used to dealing with water treatment in a commercial setting and I have some experience having to deal with EPA rules and regulations. So maybe I am not a good representative of the average public in that regard. At least one lady who writes on preparedness topics and who was trying to understand how to use pool shock found the EPA directions pretty confusing. To quote from her post on the subject……
“Being an accountant, I like to deal in absolutes so what is this business about “one heaping teaspoon”? Plus, what’s up with the references to “approximately” and “roughly”?
I decided that it was time to do my own testing, and sure enough, each time I measured out a heaping teaspoon, I had different results; they ran the gamut from 1 1/4 teaspoons to 2 teaspoons. This made my head hurt.
Another thing. Over and over I read that you should use pool shock that is a minimum of 78% calcium hypochlorite with the balance being inert ingredients. Fair enough, but there are two problems with this. First, what you find locally maybe 68%, it may be 78%, or it may be something else. Second, the EPA makes no such recommendation or at least none that I could find. They simply say “high-test”.
Her conclusion is that since the EPA says approximately all over the place, then it does not matter if the measurements are precise. She goes on from there to translate the instructions as best she can. She mixes up a glass of water and does not get sick and declares it a success. But she never seems to stop and wonder why it does not matter if the amounts are precise or just how much slop there is before you get yourself in trouble.
In one sense, it does not matter. Her instructions are no more wrong (or right) then the EPA’s instructions. But if she understood what was going on, she would understand that her instructions (and the EPAs) could lead to people getting seriously sick. That does not mean that they are wrong, it just means that sometimes in life there is no straightforward answer that is guaranteed to keep you from harm. That is why it is as important to understand the “why” as it is to understand the “how to.” Only with this understanding is it possible to know what limitations of this method are (or anything else you are taking from an authority for that matter).
So let us take a step back try to understand why the EPA instructions are like they are. We will start by relating this to something that we are already familiar with. I think most of us understand that municipal water authorities treat their drinking water with chlorine and it is kind of obvious that pool shock is used in pools. Therefore, it seems that our first step to understanding the EPA directions would be to compare them to how pool water and drinking water are treated.
To make this comparison, I am going to have to convert the EPA instructions into parts per million (ppm) as that is how I am used to thinking about drinking water and pool water treatment. Now it is late at night and mixing up your conversions is one of the easiest mistakes to make so it is possible I am going to screw this up. If so, let me know…..
With that disclaimer out of the way, this is how I understand the EPA instructions in ppm terms. As I read it, the wording “calcium hypochlorite has available chlorine equal to 70 percent of its weight” is defining how strong the pool shock is in the EPA calculations. If I am following the EPA math correctly, they are saying mix some pool shock that they have defined as 70% effective (probably because that is an average of the strength that is commonly available) in water to make a 500 ppm (parts per million) free chlorine solution and then dilute that solution down in the water you want to purify to 5 ppm.
To put this number in context, New York State DOH (department of health) does not allow water services to provide water that has on average more than 4 ppm chlorine in it (although this regulation is pretty toothless because you can exceed the 4 ppm limit all the time as long as your average for the month is just below 4 ppm). New York State DOH does not allow pool water to exceed 5 ppm of free chlorine in your pool. If memory serves me right, other states don’t allow pool water to exceed 3 PPM. In other words, the EPA is telling you to make a pretty strong solution by most regulatory standards.
So why is the EPA telling you to put so much chlorine in the water compared to what other regulatory agencies allow in other contexts? For that matter, how much chlorine is needed to kill the nasty stuff in the water? Surly this has an answer somewhere on the internet.
And in fact, the Center for Disease Control does provide an answer to that question. As we read here…..
Free Available Chlorine Germ-Killing Timetable
E. coli 0157:H7 (Bacterium) less than 1 minute
Hepatitis A (Virus) approximately 16 minutes
Giardia (Parasite) approximately 45 minutes
Cryptosporidium (Parasite) approximately 15,300 minutes (10.6 days)
Notes: Times based on 1 ppm free chlorine at pH 7.5 and 77°F (25°C)
Now by looking at the above information you should notice a couple of things. The first thing you should notice is that there is a time associated with how long it takes chlorine to kill various nasty things. This should clue you in to the fact that the longer you give chlorine to do the job, the better job it will do (and this is my biggest problem the EPA instructions, why don’t they tell people to let the water sit like they do with their instructions for liquid chlorine?). Another thing you should notice is that level of chlorine in the water for the CDC’s table is only 1 ppm and that is far lower then what the EPA told us to put in. So that brings us back to the question, why is the EPA telling us to put so much in?
To a certain extent, you might think is because of Cryptosporidium. But that is a red herring. You are not going to kill Crypto with chlorine and still have the water be drinkable (at least, not if you need the drinking water that day). And this one reason why even if you follow the EPA directions you could still get sick. But we will come back to Crypto. For now, let us focus on the term “free chlorine” and the fact that PH is defined. This should make us wonder “why is does chlorine need to be free?” and “why is PH related to how fast chlorine kills stuff?”
For our purposes, both of those questions have the same answer (it is a little more complicated when it comes to pools and such). And the answer is that it is not enough for chlorine be in the water, it also must be in the water in a certain chemical form. And chlorine’s ability to be in the water in that chemical form is heavily limited by the PH of the water. As you can see from this chart, chlorine’s effectiveness drops like a rock starting 7 PH. Roughly speaking, chlorine is twice as effective at 7.5 PH as it is at 8 PH.
So what is the PH of the water you are treating in an emergency? You don’t know and the EPA does not know either. If you search on line you will see a lot of people saying that PH of surface water (the most likely source of emergency water) can range from 6.5 to 8.5. But both the Canadians and the State of Texas say that pH of surface waters is generally between 5 and 9. That is a big range. If you are using chlorine at the top of that range it is almost worthless. If you use it at the bottom of that range and wait for awhile at the EAP dosage level you might even have a shot at killing Crypto. But without testing equipment, how do you know what you are dealing with?
And that is without getting into all the other things that can impact chlorine effectiveness such as organic load or the actual active level of chorine in the product that you are using to treat water (I know that liquid chlorine labels are not very reliable but maybe pool shock is more reliable in that regard). This is why nobody who is a professional treats water with chlorine without lots of constant testing. You just don’t know what the chlorine is actually doing in the water unless you keep testing the water with a calibrated test kit with non-expired reagents and measure things like free chlorine and PH levels among other things.
But the EPA is not talking about a normal situation. They are talking about an emergency where you lack a good source of drinking water and don’t have a lot of options. So their approach is to tell you to find as clean water as possible and load it up with as much chlorine as can be reasonable passed through the human body and hope for the best. Odds are, your water will not be on the extreme of the PH range, hopefully there will be no Crypto in the water (it comes from human and animal feces if you are not aware), hopefully the strength of your active ingredient will be roughly what it says on the label (don’t have any experience with pool shock but this is a big problem with liquid chlorine in my experience). In short, the high chlorine levels that EPA is calling for gives you a wide safety margin that will cover most issues short of Crypto. And worst come to worst, and you do get Crypto healthy people generally survive that (although an emergency situation is a bad time to have it) but nobody survives without drinking water for very long.
So the EPA instructions are not a bad compromise between risk and reward for people stuck in an emergency situation and don’t know what to do. Their directions are not precise because absent test equipment, there is no way for sure how much you need. In the real world, balancing risk and reward is the best you can do in emergency situations. And honestly, the situation is not black and white in the non-emergency world either. I have see lots of well test reports come back bad (high bacteria counts and other such things) on wells where people had been drinking the water for a long time with no apparent ill effects. You just don’t have black and white answers on what the human body is going to be able to take.
But there is a difference between what you have to do in an emergency and what you can do if you are preparing for an emergency. If I was actively storing up pool shock to use in an emergency situation, I would want to know more information. I would want to know what the PH of the surface water was in my area. I would want to use some of the pool shock that I was planning to store to use to mix up a batch in non-emergency conditions so I would know the actual ppm of free chlorine that was produced with the pool shock that I had and not the theoretical 70% stuff that the EPA had. And most of all, I would want to understand why I was doing what I was doing and not just blindly follow what the EPA said.