Water Hammer

Yes, water hammer can damage pipes. The hard vibration can loosen fittings, even sweated fittings.

Will it happen? No one can tell for sure, but it's not something that you want to leave to chance. If possible, install a water hammer arrestor as close to the problem device as possible.

An option to try first is to turn off the main shut off and open *all* faucets to drain the system. Don't forget the outside spigots. Might as well flush the toilets too.

Wait a few minutes and then turn the main back on. Close the faucets/spigots, starting at the lowest fixture and working your way up. Don't forget the outside spigots as you work your way up.

Some older houses are plumbed with air chambers - a short (~12") piece of capped, vertical pipe. These often get filled with water and no longer do their job. Draining the system basically "resets" the air chambers.

Or return the timer and try a different (more expensive?) unit.

Thanks. I figured it best to return the unit. My house has the older air chambers. I doubt there are air chambers by the garden spigots but the connections are in the walls so can't tell for sure. The line I used the timer on runs about 30' and I could hear the pipes vibrating. I'll look for a timer that has a slower shut off although I'm not sure how I'll be able to tell.

Would it be practical to add an air chamber? I guess another term for them is water hammer arrestor.

Would it be practical to add a water hammer arrestor?

I ordered a different timer that is said to not cause water hammer. If it is still an issue I'll get one of those arrestors.

On Fri, 18 Jun 2021 16:00:06 -0700 (PDT), Dean Hoffman posted for all of us to digest...

although I'm not sure how I'll be able to tell.

That is what I was thinking. It could be as simple as a piece of tube/pipe/hose vertically for a foot or so inside/outside the house. We don't know the particulars of your house so it a SWAG. It would behoove you to empty the chambers that exist presently.