To conserve water, we bathe all our kids (sans infant) in a bucket. First the 2 year old has his bath, then the 3 year old, and then the 5 year old gets the bucket topped off with hotter water.
Bucket-baths do three wonderful things:
1. Save TONS of water. The amount we use doesn't even come close to filling the tub.
2. Keeps the water warmer longer, because there's less surface area to allow for cooling. GREAT in winter months when kids get chilly fast in a shallow pool of water.
3. Gives the kids a nice soak in a spa-like environment so they're relaxed and toasty before bed.
4. I had to edit to add a fourth wonderful thing: The bathtub gets scummy/dirty waaaay less often, which means less cleaning for me!
http://i57.photobucket.com/albums/g2...bucketgirl.jpghttp://i57.photobucket.com/albums/g2...s/killian1.jpg
ETA: To answer the OP, no, I would not let my kids bathe in day-old standing water, esp considering that toddlers tend to pee in their bathwater.
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