Hello, grateful for some urgent advice please! We've had a new bathroom installed, about 6 month ago. It's done really well, but one thing that has become a problem is the loud tapping, ticking that happens when warm or hot water run from the sink drainage to the soil pipe. It doesn't happen when we just run the hot water and trap it in the sink, only when it's released down the drain pipes and to the large soil pipe and it lasts for several minutes after, sometimes even for twenty minutes. It's pretty loud and feels like something is either dripping very hard or tapping and ticking. I've heard it could be water hammer or heat contraction but how do we fix it as it's all tiled and boarded up? Is there anything we can do? We could potentially try access the pipes from the room behind but that sounds like a big headache and cutting out the wall of my toddler's room? The shower incidentally does it too but noway as loud or noticeable. Please do help as it's driving me and my family mad!