While I admit I do sometimes pick up pool supplies at Walmart, this is where I come when I really need advice on whatever pool problem I'm having that week (and there usually is a problem.) They test your water for free, and have been very helpful diagnosing different pool maladies. Their prices are a bit higher than walmart's, but the advice you get is worth it. They once spent 20 minute on the phone with me trying to help. Only downside, they don't do house calls.