Chlorine reading going up?

[Matrioux]

Hey all,

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.

 

[oldguy70]

I take all my readings, when all chemicals mixed well and 1/2 hr before the pump shuts off.....Consistent, repeatable, accurate

 

[Matrioux]

Problem with before is that my system is making chlorine so the reading will be high because of return jet location and circulation.

 

[pooldv]

Having an extra 1 or 2 ppm of FC isn't too big of a deal. There are only two options I can think of, run your pump to mix the water or brush the pool to mix your water. Take samples from a couple of places and use the lowest one to make sure FC is at target and doesn't drop below minimum.