Chris, I would think the constant flow of fresh water would cause all the natural bacteria to not effectively do its job. I didn't see in your back yard while we there but do you flowers around your sidewalk or back deck? if so re-route the drain and build a french drain, dig a trench about 1.5-2 feet deep and get 15-20 feet of field line with a a 90 deg angle turned up to catch water and a cap on the end put a layer of pea gravel in bottom and cover with the soil removed for trench. I had to do this on the side of my house because of the red clay not draining well. It's also a good idea to take your hose and blow the crud out of the drain line periodically and put some bleach thru it also to clean up the moldy slime growing in there.
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