We live in a semi, and our neighbours recently got a new bathroom. Since then, every time they use the cold tap in their basin, we hear a loud gushing noise of water flowing through pipes - it sounds like it's right under our bedroom floor. The problem is they get up around 5.30 - 6am and run the tap, and the noise wakes us up. It's also bad if they flush their toilet, but it's not as noisy when they run the tap downstairs. We've tried partially closing their stopcock to reduce the flow of water but the difference in noise level is negligible. Any ideas???