Ummm...
Over engineering a wee bit, perhaps? Even if your system runs a four to one ratio, if you need 100 gallons a month for your system, ( three gallons a day evap ) you only sent 400 gallons down the drain. That's the equivalent of flushing an "old style" toilet ( 20 to 25 litres ( four to five gallons )) twice a day. Its equivalent to watering the lawn for around an hour and a half. It's equivalent to two loads of wash in a top loading washer with it set for double rinse. It's more than enough to raise a 14 by 28 swimming pool two inches.
According to "wiki answers", the average cost of water in the United States is $1.50 per 1,000 gallons.... So, basically, you're worried about a cost of less than two bucks a month.
I can appreciate the feeling that watching the waste water go down the laundry tub drain is "just wrong", but unless you're going to make sure that every toilet is a low usage ( 1gal flush), use wild grasses on your lawn, so that you never have to water, get rid of the top loading washer and replace it with a front loading energy efficient one, put a low flow shower head in every bathroom and only run the water to get wet and then turn it off until you're ready to rinse, run your house gutters through a filter and then into your pool, etc. Then the only thing you can do, to ease your conscience, is to either run it into the washer, or store it for indoor plants, or, if you really want to send it on it's way with a "bang" throw it down a toilet instead of using the water in the tank to flush.
The only other side to this that I can see is that some municipalities charge ( like mine ) 85% of water in as being the rate for sewage use. That sucks when you fill the pool or water the grass, or top off the tank, because none of that actually goes down the sewer. But, on the other hand, some municipalities, don't meter the water, it's included in the taxes.