Knock Knock…What’s Leaking?

My plumbing pipes bang since I installed a new front loading washing machine.

Many people who have installed similar machines have the same question. You are experiencing water hammer. This is a serious problem, which should be overcome as soon as it is possible. The noise that you hear is caused by the sudden closing of the machines solenoid valves. This causes massive pressure changes in the water piping. The result can be broken or leaking pipes. Can’t you just hear the whisper of running water while you’re still at work?

This problem can be overcome by the installation of water hammer arrestors, which are also called shock or surge absorbers. In the case of frontload washers they should be installed on both the hot and cold water lines just before entering the machine.

High-efficiency dishwashers often have the same problem. 

The cure is the same. The water hammer arrestor is needed, on each line, at the point where waterlines enter the machine.

Some homes never have the problem, simply because the installing plumber has installed a whole system surge absorber on the first vertical pipe after the water meter. So, you have a choice of installing a surge absorber large enough to service all plumbing in the house or individual units at the offending appliance. This is not an easy decision. To be sure you do not make the wrong choice…

As always, you will save time and money by calling an expert!

Doug Hastings
MN Home Inspector, Minneapolis & St. Paul
ASHI certified inspector, ACI
Kaplan University, Home Inspection Lead Instructor

Rob ‘Pops’ Leslie
Kaplan Professionals, Retired


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