A high rise apartment dweller contacted me recently complaining of noise from pipes knocking at all hours of the day. He noticed that it happens whenever the taps are shut.

The Water Hammer Explained

Water “Hammer” is common in modern homes and high rise apartment blocks.

In many instances it is difficult to control, especially in high rises. It is usually caused by a combination of high water pressure in the hot and/or cold water supply pipe lines and fast closing taps and valves that “slam” shut, causing the water flow to stop instantly, thus delivering that shuddering or “Hammer” throughout the building.

These taps, like the mixer style tap in your kitchen sink or shower/bath or individual taps with ceramic discs are “fast closing”.

To reduce the hammer effect, turn them off gently…

Normal taps, or taps with washers are slow closing so they rarely cause the
Hammer effect.

Automatic washing machines and dishwashers have solenoid valves that slam shut when they have enough water.

There are various methods of reducing the pressure. Every apartment is “joined” by the pipeline that passes between the floors supplying water through the branches, to each unit.

Each apartment will have a control valve (to shut off water in the event of
maintenance or an emergency). This valve may be causing the hammer. So, depending on the hydraulic design, in a tall building there may be a holding tank on the roof.

The water is pumped up to this holding tank and from there it runs through
“droppers” to each quadrant of the building, delivering the (head) water pressure.

The greater the head, the greater the pressure, the greater the chance of
The water hammer!

Each individual unit owner may take care to fit pressure limiters and treat their taps with care. But if the tenants in the units, several floors above or below don’t take the same care, the hammer will be transmitted through the pipeline and building.

Loose pipes can contribute to the water hammer sound if they have insufficient pipe saddles/clips to hold them down and prevent movement (banging together or with nearby walls).

Control valves on water heaters and hot water pipes are also a potential source of the water hammer phenomenon.

In summary, this is not an exact science. By putting pressure limiters on those appliances that are appropriate and turning off all valves/taps with ceramic discs a little slowly will produce immediate results.

But everyone in the building will need to work together on this.

I hope that helps!