Water hammer is that loud, banging noise you sometimes hear in your plumbing and can cause damage over time. Read this article for everything you need to know about water hammer!
Key Takeaways
- Water hammer comes from quick flow changes that make pressure surges.
- It can gradually damage pipes and equipment.
- Careful design, operation, and arrestors can prevent it.
- Diagnose issues by listening for noise and checking for damage.
- Solutions range from programming tweaks to big system redesigns.
What Causes Water Hammer?
It happens when moving water suddenly starts, stops, or changes direction. The sudden action sends a shock wave through the pipes. This can be surprising—and even damaging over time (as a matter of fact water hammer can literally blow pipes apart) —but understanding what causes it can help you prevent the issue.
Quickly Closing Valves
One of the most common causes of water hammer is shutting off a valve too quickly, and there are quick-closing valves, such as ball valves. A ball valve opens or closes by a mere quarter-of-a turn. When water is flowing at high speed and the flow is suddenly cut off—like when you turn off a faucet or an appliance stops drawing water—the water has nowhere to go. It slams against the closed valve creating a hammer of water that rattles the pipes. The faster the valve closes, the stronger the shock, the louder the noise, and the greater potential for pipe damage.
Likewise to the above, if water is opened quickly, it rushes through the pipes slamming on any bend or obstruction (like a capped outlet or closed valve).
Examples Of Extreme Water Hammer
An extreme example of when water hammer can occur and result in damaged pipe is when a fire hydrant is turned on and off, or when a city water main is turned off and then on.
- Fire Hydrant: If a fire hydrant is turned off too abruptly the water rushing through the pipes will cease to have an outlet. That pressurized water will then come crashing into any elbow or “stop point” seeking an outlet. This can cause city water mains to burst apart, or home water service lines to leak.
- City or Public Water Mains: If a city or public water main has been turned off, it must be reopened slowly, and with the air inside the pipes allowed to escape from open hydrants. If the water is turned on abruptly, and with no outlet for the air, water hammer will be extreme. This can easily blow apart water service lines, or the main line itself.
Pump Failure or Sudden Stoppage
Another cause of water hammer is an unexpected pump failure or shutdown. Since the flowing water retains kinetic energy and momentum, it continues to push forward when pump operation ceases. This abrupt change in flow direction causes pressure fluctuations and vacuum pockets that lead to loud banging noises as the pipes shake in response.
Steam Hammer
In piping systems that transport steam, water droplets can form and get carried along by the high-velocity vapor flow. When these liquid “slugs” encounter bends or obstructions in the pipework, the force of impact causes an especially loud hammering noise known as steam hammer.
Overall, being aware of what causes water hammer can allow homeowners to take steps to minimize or resolve this common plumbing nuisance. Simple precautions like closing valves gradually and maintaining pumps can go a long way toward preventing disturbances.
Other Factors
Certain things make water hammer more common:
- Pipe types and size – water hammer occur in plastic more than metal, and in smaller diameter pipes
- High-viscosity liquids like oils
- Fast moving liquids
- Use of quick closing valves like ball or swing check valves
- Poor high-temperature drainage pipes leading to steam turning into water pockets
- Loss of air cushions in steam pipe traps
The Effects of Water Hammer
While the noises may not seem like a big deal, water hammer can cause some serious damage after awhile.
- The effect of high-speed water hitting an elbow or capped end can blow pipes apart.
- Pipe weakening – Water hammer fatigues joints and seals over time.
- Pipe leaks or breaks – Pressure spikes from water hammer can lead to leaks or pipe ruptures.
- Equipment damage – The impact can hurt attached equipment like valves and flow meters.
- Property damage – Water leaks can harm electrical systems nearby.
- Safety issues – Pipe bursts may release hot water and cause injuries.
So its important to address water hammer since it could mean pricey repairs later on.
Preventing Water Hammer
Luckily, there’s several ways to prevent, reduce, or control water hammer. Ine of main ways for a homeowner to prevent water hammer is to very slowly open or close a gate type valve. In addition, when doing so, always open a faucet or two on an upper floor to relieve the potential of built up water pressure.
Proper System Design
Good defense is designing pipe systems right initially:
- Water hammer arrestors (see below) are specifically designed to create open pockets, or cushions of air, for sudden increases in water pressure to find relief.
- Optimal pipe sizing – Avoid fast velocities above 5 ft/s.
- Add loops, elbows, branches containing air- this lowers pressure wave movement. Remember, air compresses, bu water does not. This means tha thigh-pressure rushing water can expand inside an air pocket.
- Prevent long straight pipe runs – More bends and shorter runs dissipate shock waves. Like more curves slow a race car on a track as opposed to a long straightaway.
Install Water Hammer Arrestors
Special arrestor devices absorb pressure spikes and decrease water hammer damage.
Proper Valve and Pump Operation
Programming pumps and valves to start/stop gradually prevents sudden flow changes.
Operator Training
Educating staff on proper startup and shutdown processes minimizes water hammer events.
Diagnosing Water Hammer
If you think you have water hammer, here’s how to be sure:
- Listen for loud banging noises from the pipes.
- Check for damage like leaks or cracks.
- Monitor pressure – Add gauges to catch spikes.
- Maybe use vibration sensors on pipes to alert on shock events.
If water hammer is causing operational problems, it might be time to call an expert to ID solutions.
Water Hammer FAQs
What’s water hammer sound like?
Loud banging, hammering, or knocking from the pipes.
Can water hammer lead to damage?
Yup, it can damage pipes, valves, pumps over time.
How do you fix water hammer?
Fixes are water hammer arrestors, good system design, valve/pump controls, and operator training.
Knowing what makes water hammer and how to deal with it will save you headaches (and repairs!) later on. Stop those noisy pipes for good with the right precautions.
