I use a hand transfer pump ... cheap enough and can take MOST of the water out of the buckets when needed. I don't tend to do a complete change of the bucket more than once or twice during my grow - and I don't worry if I have to leave some old water in the bucket.... This is what I use - https://www.amazon.com/Liquid-Fuel-Transfer-Siphon-Pump/dp/B06XKHP8Q4/
Good luck!