There is no chlorine registering in my pool. My chlorinator is on, and I have just shocked the pool. What's going on?
Chemistry test
When testing your swimming pool water for "available" or "free" chlorine (CHL) you are measuring the amount of chlorine that is in the pool and is ready to attack a waste. If your test indicates 0.0 CHL there may be chlorine in the swimming pool working to sanitize the pool BUT there is no extra, "Free", or "Available" chlorine to attack new or additional waste. In this state
it is possible to have a perfectly clear and clean pool as well as SMELL chlorine (really chloramines) but not have any free chlorine register on a test.
Chloramine molecule
Think of your swimming pool chemistry and chlorine like your immune system. If your immune system is healthy and ready to fight germs it is possible for you to fight off a cold you picked up from a door knob or other source and not even know it. Similarly, if your pool is healthy and has an available CHL level (1.0-2.5 PPM), it can also fight off algae or other contaminates from bathers and not get "sick". However, if your body has been fighting off multiple colds, and you are exposed again, it may be too much for your immune system can handle, and you may become sick. This is probably the time to see the doctor and start taking vitamins and or medication to give your system a boost. Your swimming pool is exactly the same. If the waste outnumbers the chlorine and the pool gets "sick" it's time for your pools immune system to get a boost. We do this not with meds or vitamins but rather by "shocking." Shocking the swimming pool is simply increasing the chlorine level in the pool to 10 PPM to kill the organics in the pool and thereby getting the pool healthy again.
Shocking can be done a couple ways. If you have a salt chlorine generator you simply push the "Boost", "Turbo", or the "Shock" button. These buttons vary by unit but do the same thing. They increase the output level of the unit to 100% for a period specified by you. The second way is to simply put granulated or liquid shock in your pool. If you don't have a salt chlorine system this is your only option. If you do have a salt system you can still add chemical chlorine to the pool and not wait for the system to do it. Either is fine.
Showering beforehand
helps reduce chloramines
Last but not least- and I don't want to get TOOO technical here- but
your pH could also be the reason your CHL is not registering. If your pH is not between 7.2 and 7.4, your free chlorine reading is NOT ACCURATE. Example: If your swimming pool has a pH of 7.2 and your CHL level is reading 2.5 you're a happy camper. However, if your pH is 7.8 only 20% of the chlorine in the pool will be available and measurable. This means your readings would be PH 7.8 and chlorine 0.6. Why? Because the other 80% is being wasted in the swimming pool and is ineffective. If you lower the pool pH by adding muriatic acid or pH minus. When you retest you find magically that your chlorine appears to have increased to 2.5. In reality the level has not actually increased but the chlorine that has been in the swimming pool all along will become usable and register. Have you ever wondered why the chemical companies suggest you keep your pH at 7.4-7.8????? You got it! So you'll buy more chlorine!!!! For more help and a guide on adjusting your water chemistry see our
swimming pool water chemistry calculator.
