Not necessarily. Was it green and nasty before draining? If so, there could be algae in the plumbing/filter which would require a SLAM Process. But if the water was clean & clear at the time of draining, you could be fine. Fill it up, adjust chemicals as needed. If you suspect an elevated chlorine demand, you can always do an Overnight Chlorine Loss Test to be sure.
Ok guys. Obviously a new full the CYA is zero - tested to confirm all good. The pool math app told me to put in 340g of CYA to bring it to 40ppm. I put in 330g and now my CYA tested a couple of times as 70??? What’s going on here??
If my math conversion is correct (8500 L = 2246 US gallons), the PoolMath tool shows me it only takes 12 ounces (or about 340g) to increase a CYA from zero to 40. So your dosage looks to be correct. Must be a testing error since I don't see any way someone/something could have added stabilizer you didn't know about.
Proper lighting is critical for the CYA test, so you want to test for CYA outside on a bright sunny day. Taylor recommends standing outside with your back to the sun and the view tube in the shade of your body. Use the mixing bottle to combine/gently mix the required amounts of pool water and R-0013 reagent, let sit for 30 seconds, then gently mix again. Then, while holding the skinny tube with the black dot at waist level, begin squirting the mixed solution into the skinny tube. Watch the black dot until it completely disappears. If it helps, pour a little, look away, then look back and pour some more. Once it disappears, record the CYA reading. After the first test, you can pour the mixed solution from the skinny view tube back to the mixing bottle, shake, and do the same test a second, third, or fourth time to instill consistency in your technique, become more comfortable with the testing, and validate the CYA reading. If you are still questioning your own results, have a friend or two do the same test 2-3 times. Share your results only after everyone is done to see if you came up with the same average results.
I did have good lighting in my previous tests but I tried it outside this time and lost 5ppm - 65ppm it’s a clear choice labs test kit so I’m expecting an accurate result. This will be the third test and they’ve all been the same so I just don’t know. I’ll have to empty out some water again
That is really odd. You have a good test kit and you seem to be receiving consistent results. Your Poolmath info was correct before, so the only other thing I can think of is if somehow you simply overdosed the water with stabilizer somehow. In a small pool it wouldn't take much.
But on a side note ... not sure if this was ever mentioned to you, but your pool is somewhat small (under 3K gallons). As such, we have a page designed for pools that size you may like to follow.