Would setting the tube on a white surface (white concrete or a printer paper) with my back to the sun be the best way to test it?
I can't figure out if I have 30 or not. When I hold the tube at the waist level the water is shaking a bit and it looks like I have 30. If I have it sitting on the concrete it's more like 25-27
I know CYA test is +- 10ppm, but would sitting bottle on the ground be the more accurate testing?