Put it in writing, keep a copy, and go one desk up.

One small thing you could do

If water is coming in anywhere it should not, deal with that first (see the safety box). Otherwise, turn off every tap and appliance that uses water, take a photo of the meter reading, and look again two hours later. Then find the date your bill was issued, and ask your water supplier whether it gives a credit for water lost to a leak and what the deadline is. If your landlord holds the account, tell your landlord about the jump instead. Keep every receipt, and give true dates.