If you can hear a banging sound coming from a pipe within your walls, it may not be as complex of a problem as you may think. This common issue is known as water hammer because the water is basically acting like a hammer as it hits against a pipe.
It’s a Pressure Issue
The water is flowing at such a high speed that when the valve is closed to turn the water off from a point within the house, it is slamming into the valve and pipe’s interior walls with nowhere to go. So, it rattles and vibrates until the pressure subsides. This can potentially wear out your valves quicker and faulty valves cause leaks. It also may weaken connector joints that result in frustrating leaks.
The best solution is to introduce a cushion of air. There are simple attachments to absorb the shock that can be installed inside the pipe near the valve. Just be sure to use a rubber bladder to prevent the air cushion from being absorbed into the water. The air needs somewhere to go when the pressure from the water pushes on it and the rubber bladder maintains the sealed system.
Another option involves turning off the water to the entire house. Then open the lowest faucet to allow the water to fully drain out of the system. You can check the other faucets to be sure they have no water left in them as well. Then make sure all of the faucets are closed again, including the lowest one, and turn your water back on. This allows air to enter the system and will hopefully provide a bit of a cushion.
If they continue to bang, your water pressure throughout the house could be too high. This is fairly common in homes located in low lying areas. It is important to address the pressure from this angle to support the integrity of your pipes over the course of time. You can attach a regulator or an expansion tank. It may be an involved process, but ensuring your home has larger pipes (around ¾ inch) can help reduce the water speed which reduces the pressure.
There is a device known as the water hammer arrester. It works by ensuring there is enough air to cushion the pressure spike when the water slams into the valve. It can be attached to a shut off valve and comes in various sizes. It is most commonly used to fix washing machine water hammers.