A beautiful Wednesday mornings weather isn’t always a so bright, and its not the case for Mrs Moore in Crowborough East Sussex on this sunny day as she has called to explain the noise from her mains water water when the toilet is flushed is continuous loud vibrating sound. After listening to the sound at the other end of the phone we were able to establish the sound as mains water hammer. Ability Plumbing and Heating have been able to book this in today for our engineer Tom who has confirmed he can attend later this morning. So what is mains water hammer? Well here is a short paragraph below to explain the basics.
Mains Water Hammer
When a pipe is suddenly closed at the outlet (downstream), the mass of water before the closure is still moving, thereby building up high pressure and a resulting shock wave. In domestic plumbing this is experienced as a loud banging resembling a hammering noise. Water hammer can cause pipelines to break if the pressure is high enough. Air traps or stand pipes (open at the top) are sometimes added as dampers to water systems to absorb the potentially damaging forces caused by the moving water.
In hydroelectric generating stations, the water travelling along the tunnel or pipeline may be prevented from entering a turbine by closing a valve. For example, if there is 14 km of tunnel of 7.7 m diameter full of water travelling at 3.75 m/s, that represents approximately 8000 megajoules of kinetic energy that must be arrested. This arresting is frequently achieved by a surge shaft open at the top, into which the water flows. As the water rises up the shaft its kinetic energy is converted into potential energy, which causes the water in the tunnel to decelerate. At some HEP stations,[examples needed] what looks like a water tower is actually one of these devices, known in these cases as a surge drum.
In the home a water hammer may occur when a dishwasher, washing machine or toilet shuts off water flow. The result may be heard as a loud bang, repetitive banging (as the shock wave travels back and forth in the plumbing system), or as some shuddering.
On the other hand, when an upstream valve in a pipe closes, water downstream of the valve attempts to continue flowing creating a vacuum that may cause the pipe to collapse or implode. This problem can be particularly acute if the pipe is on a downhill slope. To prevent this, air and vacuum relief valves or air vents are installed just downstream of the valve to allow air to enter the line to prevent this vacuum from occurring.
Other causes of water hammer are pump failure and check valve slam (due to sudden deceleration, a check valve may slam shut rapidly, depending on the dynamic characteristic of the check valve and the mass of the water between a check valve and tank).