Hi there, looking for some advice. Our neighbours had a new bathroom fitted last year & ever since every time they flush there toilet it makes a loud banging sound. It seems to be getting worse & wakes us up every night. We have mentioned it to them a few times but they have done nothing about it. What is causing it & could it be damaging our pipes as we share the same drainage system. Any help is appreciated, thank you.

Could be water hammer but without knowing what the "neighbours" issue is hard for us to guess. Do you share the same water supply? If just the drain is shared, I don't anticpate problems with your water system.

ma0641 nailed it. You're OK on the drainage. Not to worry. It does sound like water hammer and if the plumber installed air chambers on the lavatory supplies, as mandated by code. They need to be recharged. If they need directions on how to recharge the air chambers have them get in touch with us. Good luck, Tom

Tom, my guess is they are on the continent. "-neighbours "Brian