What is a Chlorine Demand? | Combined Pool & Spa

What is a Chlorine Demand?

We are just finishing up all of our pool openings this year, and it was one of those years that it wasn’t that cold of a winter, and we are opening up a lot of pools with chlorine demands. If you have never heard the words chlorine demands, basically what it means is something organic has died in the pool. It can be something as awful as a snake, rabbit, or bird or something as simple as leaves. Basically it is just something organic, that may even be microscopic and you can’t even see, that has died in the pool. What that has done is it has actually taken the chlorine and it has made it go negative. So if you put a shock in a pool a typical shock is one pound per 10,000 gallons. If you have a 10,000 gallon pool and you put one pound of shock in and you don’t have any chlorine showing up, you are probably looking at a chlorine demand. So at that point you can do up to 3 times the shock at one time, so you can put 3 pounds of shock in at 10,000 gallons. You can put in three pounds and wait about 5 minutes and use a really good test strip that tests for free chlorine. You want to test your pool and if you don’t have a 10 part per million you need to redo this process again. You have to wait about 2 hours between each addition of shock, but you want to keep doing it till you read a 10 part per million, and that is the dark purple on your test strip. Once you get that reading you need to hold that for about 2 hours, and you don’t want to drop below 3 parts per million for the next 24 hours.

With that being said sometimes a chlorine shock can be nine or ten pounds of shock, other times we have seen 100-300 pound shock chorine demands. If you are putting in a lot of shock, you need to make sure you are using a real good quality shock like Bioguard burnout 73 or something along those lines as opposed to a real quick shock and swim. If you cannot seem to get to the 10 parts per million you can bring in a water sample to Combined Pool and Spa and we run a chlorine demand for you. This test does take a couple of hours, but once this test is ran we can then tell you to the poundage of what it is going to take to reach those levels. If you have any more questions come check us out in store or on our Combined Pool and Spa webpage.