do you mean test the runoff of a pot filled with soil, before you introduce the plant? Thats a good idea...kinda like washing your soil! I have been using tap water that I let sit out for about 24 hrs to allow any chlorine to evap. Unfortunatley I dont have a 15 gallon container...the largest I have is a 2 gallon water jug. Hopefully I dont create bigger probs by not letting the chlorine evap.

Thanks for your help!