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I don't have the patience to read this thread with a fine toothed comb but it looks like part of the cost of the water is the sewer rate factored in. I hate to nip pick but I would never bother to send the water down the drain. I've always recommended people water their plants with that drained spa water by letting the sanitizer level drop before draining (it ends up being far lower than the amount of chlorine in the tap water).
I don't have the patience to read this thread with a fine toothed comb but it looks like part of the cost of the water is the sewer rate factored in. I hate to nip pick but I would never bother to send the water down the drain.).