Why! Why! Why! No Chlorine Reading on my Test Strips!

Here's the situation:

"Why when lots of shock was added to the pool and I know it's there, I get no reading on 3 different test kits.  I tested immediately after adding the shock, I got a reading of 10 (extreme high). In 5 hours no reading at all (extreme low). I used shock from two different sources. Also, I never had this problem in 30 years." 

It's not the product.

It's not the test kits. 

You simply have not added enough chlorine!

You must add enough chlorine to react with all of the organic matter, algae (live and dead) and wastes in the pool, pipes and filters. 

Green pool. Cloudy pool.

Obviously, if the pool is cloudy or green with algae, you will need to add large doses of chlorine shock. It's easier to understand why you can't establish a chlorine reading if a pool is in that type of condition and obviously needs extreme chemical treatment.

Clear pool.

However, you can have a clear pool and not be able to establish a free chlorine reading.  The pool appears clear. Yet no reading on your testing equipment. That's because what you can't see is microscopic in size (bacteria and particles). By the way, if I looked at your "clear" pool, I would probably not consider it clear, but dull looking. An officially clear pool is CRYSTAL clear and sparkling!

So then, how do you know how much is enough?

ANSWER: Until you get a free chlorine level to last through an overnight period, you will probably not have added enough. 

For the best results bring a sample of your pool water to PoolCo for a complete computerized water analysis. We will customize a plan and diagnose proper dosages for helping overcome this chlorine demand situation. Best of all, the test is free!

As for why this has never happened to you before: 

There could be many explanations for why you never had the problem before. Closing too early in the fall or opening too late in the spring. Winterizing chemicals only last for a very short time once the water under the cover begins to heat up. Older pool cover with pin holes?

SAFETY NOTE: NEVER Add shock through the skimmer! Always add pool shock to water, either directly to the pool or add to a large bucket filled with water.

Pool equipment and chemical manufacturers advise not to do this, as it may damage equipment or cause a dangerous chemical reaction.