I'm giving up and closing the pool this weekend. I have had the same problem all year of not being able to keep chlorine in the pool. I can double shock the pool at night and by morning it's gone. I had my water checked and everything was fine. I finally decided to test for nitrates and the reading was in the 10-20ppm range. I heard if you get a reading at all its too much so I drained half the pool water and refilled it last weekend. Afterwards I tested for nitrates again and got the exact same reading. And yes I tested my tap water which showed zero nitrates. Since then I still have the same problem. I shock the pool and its gone in hours. Here are my latest test results for my 17,000 gallon above ground pool:
Calcium Hardness- 120
Total Dissolved Solids- 600
My water is clear but every couple days I can see algae starting to grow again because I can't keep the chlorine up. I bought some product to increase the hardness. Should I increase the TA? What do you recommend when I close the pool? Should I bombard it with bleach and hope for the best? Thanks and good riddance to this season!