I have a small bucket that I carry with me to the pool specifically for the test water and the first rinse after completing each test. When I'm done testing, I dip the bucket into the pool to fill it ~1/2 way (to dilute my little testwater cocktail) and then find an inconspicuous place to dump it - if there's some gravel or a rock on the edge of the property, that's my 1st choice. Dumping the tested water back into the pool is a big no-no, if for no other reason than the pH test negates the alk test (just do both tests back to back and dump the water into the same bucket; red + red = green )