A Deep Well is an improved source of water which is created by adding a stanchion kit to an empty shallow well. A Deep Well can only interact with a Bucket. It has 4 lots of water with a 25% chance to use, meaning it has an estimated 16 uses before it dries up.
You cannot multiply water by taking it out and putting it back in. Due to the chances, you will mostly likely lose water if you put water back into wells. It takes 7 hours for a deep well to gain +1 unit of water. Dry Deep Wells take 30 minutes to regenerate +1 water, so adding a water back into the well will only make it regenerate slower. Emptying the contents of a well into Cisterns will speed the rate of water regeneration.
An empty deep well can be upgraded into a Newcomen Pump. Once the first Stone Block has been placed, the water will not regenerate.