[Skytrooper]

While not a pilot, I was a UH-1H crew chief. I have preformed hundreds of fire bucket drops. Yup, hundreds. My best day was 103 drops , that fire was only 1.5 minutes from the mountain pond we dipped out of. I was also the aircrew and fire bucket trainer (FE/SI).

To answer the OP’s question, the release of the water goes through the restricted dump valve on the Bambi Bucket. Therefore it slows the weight decrease. It is not like just punching off (jettisoning) the entire bucket water and all. There was never any perceptible vertical rise of the aircraft. We were also flying forwards ( low and slow) as to make a decent dispersal of the water.