Try a chlorine bleach and water mix to kill and odor causing bacteria, mold, and fungus and flush your drains all around the perimeter with it and let it sit for a while. Go to walmart and buy a little bag of straight clorine pool treatment for a couple/three bucks. Be careful, it is strong and powerful stuff and doesn't need much. Don't get it on you. I think a small bag will treat about a 10,000 gallon pool but it is cheaper than clorox.