[reveivl]

What are the causes of water hammer?

 

[plumguy]

Quick acting valves and high water pressure will also contribute to water hammer.

 

[reveivl]

More info

This residence went for 20 years without a problem including five years or more after they bumped the pressure up around 90lbs. All the faucets are the old fashioned washered ones. One day she started getting hammer, and two days later I get the call that the pipes have blown in the crawlspace. Found the culprit, VERY poor soldering: piece of soft copper bent too close to the fitting, only went in a little more than 1/16", and the solder was used more as glue than solder. Took out the entire mess and replaced with new. Curious to learn from a real plumber why the hammer might just start up like that. There's no arresters in the system 'cos she never had a problem until now. Any ideas? Rich.

 

[plumguy]

Excessive pressure which would be anything over 80psi here can cause wear and tear on fixtures and valves. It sounds like her problem is a loose washer in one her faucets or valves and is causing water hammer like symptoms.

 

[Teetorbilt]

90 PSI is very high. Pressure is usually around 80 near plants and towers and should be at least 65 for municipal systems.