Based on the level of respect or formality, you can say "Can you please refill the water for me?" in Korean in 3 ways:

• Informal: mul jom chaeweo-julrae? (물 좀 채워줄래?), mul jom chaeweo-jul su iteo? (물 좀 채워줄 수 있어?), mul jom chaeweojul su itni? (물 좀 채워줄 수 있니?)
• Formal: mul jom chaeweo-julraeyo? (물 좀 채워줄래요?), mul jom chaeweo-jul su iteoyo? (물 좀 채워줄 수 있어요?), mul jom chaeweo-jul su itseupnigga? (물 좀 채워줄 수 있습니까?)
• Very Formal: mul jom chaeweo-jusil su itseupnigga? (물 좀 채워주실 수 있습니까?)

- can do: hal su ittda (할 수 있다)
- you (subjective): neo (너), neo-neun (너는), dangsin-eun (당신은), dansin-ggeseo-neun (당신께서는) - omitted here
- water: mul (물)
- to refill: chaeuda (채우다), chaeweo-juda (채워주다)

Please refer to How to pronounce Korean Alphabet for the English pronunciation in this answer.