Hi MCO . ..

I'm not sure what you mean by your numbers jumping around. They look really stable to me.

7.4 7.8 7.7 7.7
100 90 120 100
300 275 320 330
100 100 95 100
700 900 700 700

That's very stable, and well within the limits of error for most GOOD test kits and pool test methods.

To put it another way, if you put a gallon jug of pool water in your fridge, kept it sealed, and then took a sample of the water to be tested 4 days in a row . . . you'd expect to see as much variability as you show, simply from intrinsic testing error.

Ben
"PoolDoc"