Hope some one can help. I have just had a new main pipe laid through my driveway due to a leak. Now when I turn on the cold tap on in the bathroom it makes a loud thumping noise, but not all the time and not always the 1st time I turn the tap on. This morning I turned it on and it was fine and then went back in 10 minutes late and turned it on and it made the thumping the noise. We have also just put in new taps in the bathroom.