Have you ever heard a sound like someone hitting metal pipes with a hammer in your home?  There’s always the possibility that it’s a ghost haunting your house, but it may also be a phenomenon in your water pipes called hydraulic shock, better known as water hammer.

Water hammer is caused when a valve downstream (typically a faucet) is quickly closed.  Even though the valve is now closed, the water in the pipes continues to move towards the valve which builds up pressure against the now closed valve causing a shockwave.  This shockwave results in the banging sound you can hear and sometimes can cause significant damage.  As an analogy, imagine that you are running towards a door and at the last second it suddenly closes.  Without enough time for you to slow down you run into the door and fall backwards.  Now, add to this analogy that you have lots of people running behind you and you push them down as you fall backward causing chaos and injury.  This is essentially what is happening in your pipes when water hammer occurs.

The simplest fix for water hammer is to give the water someplace to go if it can’t go through the valve.  Water hammer arresters are small devices that have a pocket of gas separated from the waterline by a piston that can move up and down compressing the gas.  When installed on a pipe, the water hammer shockwave would push against the piston, compressing the gas temporarily and dissipating the shockwave.

If you hear any bumps in the night this Halloween, you may just need to install some water hammer arresters.  If you’ve already done that, then you might want to look at moving since your house is probably haunted. Happy Halloween from your friends at Forward Engineers!