Plumbing/fixtures hammer after irrigation pipe install

Problem did not exist beforehand. Landscaper (not me) simply tied into the riser of the backyard bib riser. The sprinkler system is on a timer. Now when the irrigation water shuts off, indoor plumbing hammers. Did not have backyard sprinklers before and the front sprinkler system has always worked fine. What should have been done or what can be done now to make this work without problems. Are arresters a probable fix? if so, where to install? On the outside bib?

Thanks folks!

A fast closing valve on the irrigation causes the water rushing through the pipe to stop suddenly - the vibration in the pipe is what you refer to as water hammer...
To solve it, get a hammer arrester and place it close to where the irrigation valve is (but before it)...
Hammer arresters work like the shock absorber in your car - soften impacts preventing damage...