I took a sample and tested (TF-100 powder test) about 15 minutes after my pump and swg stopped running and got a reading of 4 (8 drops). An hour later (no pump in the meantime, no SWG, plenty of sunlight around lunchtime) same spot/depth in the pool tested at 6 (12 drops). Any ideas? I have also noticed that if I take a reading in the afternoon/evening shortly after the pump stops, and again in the morning around sunrise (nothing is currently running at night) I also sometimes see a rise of 1-2 ppm in the test. If the difference was only a drop or two I would call it my error, but the difference is often 4 drops or more (2 ppm)
Is this a striation/circulation issue with the pool? is it taking that long to distribute fully around the pool? Or does chlorine rise towards the surface and that's why my reading goes up after the water has been still for a while?
Readings are always taken from the same spot in the deep end (6' pool depth). I put my hand in the water up to my elbow (about 1 foot deep) and fill the sample container from there.