What is a water hammer

You may feel worried if you hear loud bangs when you turn off your tap. Perhaps it's a sign of something wrong, you think. Your instinct is likely correct. The sound may be from a water hammer, leading to serious plumbing issues like leaking taps or burst pipes.

So, what is a water hammer? Read on to get an answer. You can also learn the causes of water hammers, the effects of water hammers, how to fix water hammers, and ways of preventing water hammers.

How does a water hammer happen?

A water hammer occurs when the pressure from gushing water suddenly stops. This stoppage is due to a valve abruptly turning off and causing the water to slam into it. In turn, the high pressure leads to reverberating hydraulic shock waves in the pipes. That's the source of the loud vibrating sounds that you hear.

The fluid in motion is forced to stop or change direction suddenly. The shock wave from the impact of the water propagates at the speed of sound. Note that a water hammer's sound differs from trapped air within the pipes. The sound from a water hammer occurs after you have turned off the valve and not after turning off the tap.

Causes of water hammers

The following are the most common causes of a water hammer:

Solenoid valve closing

The taps of your dishwasher or washing machine usually have high water pressure due to flowing water. A dishwasher solenoid valve closing can cause a water hammer effect.

In fact, the most common valve that causes a water hammer in homes is the valves from these appliances. Remember that washing machines have two shutoff valves, and dishwashers have one.

Air loss in the air chamber

In a normal situation, the water pressure effect is cushioned in the air chamber of plumbing systems. The air chamber is useful when you shut the valve or close the tap. However, if the air pocket is lost, a water hammer occurs. You can drain the air chamber to absorb the shock of water.

When filling empty pipes

Another occurrence of the water hammer effect is filling water into empty pipes at high rates. The air gets out through a small hole, and when it's all gone, the water flow is suddenly stopped. This leads to a pressure surge.

The following situations can also cause water hammers:

• The flowing fluid stops abruptly or is forced to change direction. This causes a shockwave, often referred to as hydraulic shock.
• If an open valve suddenly closes.
• If water recombines after water column separation.
• A pump that suddenly shuts down and the flow direction is reversed back to the pump.
• Worn ball/float valves of water tanks or low-pressure valve nozzles.

What are the effects of water hammers?

The impact force of a water hammer on the valve creates pressure spikes from the stoppage of fluid flow. These pressure spikes can be over ten times the standard operating pressure. Both the flow stoppage and the resulting shock waves from the increase in pressure can cause significant damage to the entire piping system.

Over time, a water hammer can cause a catastrophic flow system failure. For instance, water leaks can lead to damaged electrical equipment or corrosion of infrastructure. The effects of a water hammer can include the following:

• Pump and flow system damage
• Leaks at joints and pipe fittings
• Ruptured pipes and damage to control valves and pressure gauges
• External property damage
• Risk of accidents from slips, falls, and electrocution
• Downtime due to maintenance

How can you fix water hammers?

Engineers in the past have consistently recognised that water flowing through a pipe has momentum. That is why the principle is applied in historical inventions such as hydrams (hydraulic rams.)

Today, you can use the following ways to fix water hammer issues:

• Restore the air pocket on the vertical risers. Opening a tap and running it for some time can help eliminate the air within the pipes.
• Alternatively, shut off water heaters and drain all the water from your property. Then turn on the water. This way, air will enter the air chambers again.
• Installing a pressure limiting valve can help you to control very high water pressure.
• Another way is to install water pressure regulators. This helps manage the overall pressure of the main water pipes.
• You can use features such as blow-off valves, expansion tanks, and surge tanks to reduce water hammer.
• A diaphragm helps stop the water flow. It's simply a flexible disk of various kinds of rubber that responds to pressure.

How to prevent a water hammer

The choice of check valves can contribute to water hammers. Some valve types, like piston-style check valves, need gravity and flow reversal to return to a closed position. This causes water to slam into its mechanism and, in turn, creates pressure waves that transmit through your piping systems.

Thus, you may want to use silent or spring-assisted check valves. They have an internal spring that moves the valve into a closed position well before flow reversal. You can also set up air chamber systems of short pipe segments.

They can serve as a cushion. These cushions act as shock absorbers that allow the water to expand and reduce the magnitude of shock. Other ways of preventing water hammers include the following:

• Old systems can be flushed
• You can install regulators and pressure reducers in the supply line
• You can lower the operating pressure
• Include air chambers in the design of piping systems
• Use silent check valves, angle seat valves, or manual ball valves (as used in drinking water systems) instead to reduce the severity of pressure.
• Installing systems like water towers, surge tanks, or expansion tanks can help capture pressure surges.
• Install water hammer arresters as attachments to your mixer taps
• Properly size your pipeworks so the flow velocity does not exceed 0.5m/s
• Exercise care when opening and closing quarter-turn valves such as plug, ball, and butterfly valves.

Fix water hammers with water hammer arrestor

Below you can find a method to fix a water hammer with a water hammer arrestor:

• Your first step is to completely shut off the water to areas that experience water hammers, such as dishwashers. Simply turn their shutoff valves clockwise. Turn hose fittings loose with an adjustable wrench and disconnect hoses.
• To install threaded water hammer arresters, thread them onto each inlet. You may use pliers to tighten them.
• You can slide the compression ring in and thread it on the compression nut for compression fittings.
• Push the fitting onto the pipe if you're fixing push-fit water hammer arrestors.
• Then use your pliers to connect the supply tube or hose to the water hammer's arrestor. Remember to tighten the connection.
• Turn shutoff valves counterclockwise to turn on water supplies.
• Inspect the entire system for leaks. You can use a flashlight.
• You can do a test cycle by running every appliance on a water hammer arrestor.

What is steam hammer?

A steam hammer occurs in steam-filled pipe systems when a part of the steam condenses into water. This may happen in a section of pipe. A 'slug' will form as steam picks up the water.

The slug is then slammed at high velocity into a pipe fitting. The result is the loud hammering noise that you hear. A cause of steam hammers can be poor condensate draining strategy and poor stream pipe system design. Another cause is the depletion of installed air traps over time.

You can shut off the steam supply and drain the pipe system to remedy steam hammers. Just open the taps at the highest and lowest points to drain it and resupply the air cushion.

A professional can help with water hammers

Having gone through this article on what a water hammer is, the effects it causes, and how to fix them, you should have some ideas on how to stop water hammers. However, the easiest way of stopping water hammers is to invite a local plumbing contractor.

They can check your water lines and provide effective solutions for different problematic sections of your plumbing systems. Moreover, they can fix other issues with your water heaters or boilers. You can even invite them for emergency plumbing services.