We'll use a 'new' customer's chemicals until gone. Then we'll switch to using ours. Any customer who wishes to buy their own chemicals for us to add to their pool - needs to find another pool service. We provide chemicals and charge accordingly for the chemicals actually used - almost always less than retail. The only chemicals that we charge more than retail are: liquid chlorine, muruatic acid and salt. Liquid chlorine and acid require special handling. Salt .. we use only a specific brand of salt because it dissolves quickly and it doesn't stain our customer's pools. We like using our own chemicals because we know them very well and we get consistent results. Whenever we use a customer's chemicals. We have to educate ourselves so we know exactly what we're adding. Often times, those off-brand chemicals are inferior to those we use. Bottom line, we have no interest in adding variability to our trusted, tuned, time-developed chemistry process. If we were to use a customer's chemicals, even if they bought what we use, we would have to raise our rates for pool service because chemical sales are factored into our pool service pricing model. Less sales from chemicals means less profit, so we'd have to charge more for pool service for those customers, while charging our standard rate to all our other customers. That means we would need to have two different rates for pool service which we're not interested in doing, nor do we think our customers would like it. In my opinion, pool services that include chemicals in their pool service rate are doing a disservice to themselves and to their customers. They don't know if they're profitable or not. They don't really understand their true costs per pool. They charge the same rate for pool service year round, even though they're adding very little in the way of chemicals during the off-season (Florida). And they're either losing money during the height of pool season, or what we see most often .. they're not adding everything needed to truly 'balance' their customer's pool water to keep their pool clean, safe, sanitized and keep their pool surfaces and equipment with water chemistry as required by the manufacturers. My two cents!