Before I get too many descriptions of a water hammer,,, I'm a firefighter, so I know allll about water hammers. And, I am aware of the 'water hammer arrester'. I have one.
This is a little different story. When I bought this house 5 years ago, all 6 valves would bang when closing. As you can imagine it drove me crazy. I called Rain Bird, with zero luck.
Finally I thought that I would just dig up the old valves and replace them, and as I got ready, I realized that it is just the guts that need changing, so I replaced the old diaphram with new ones. It worked! Absolutely blew me away, but I was so pleased that I didn't question why.
About two years later I started getting the banging again, but this time, I found a supply place that sold diaphram kits.
Now I am starting to ask questions. I still have one valve (the last one in line) that bangs when closing if it doesn't get a new kit every year. Why would this be necessary? I went 16 years in my old house with the same valves and I never changed the diaphrams. It is a simple fix, but it shouldn't happen this often.
I have two adjusting valves (screws) on top. One lets me turn the system on to test it, but for the life of me I don't know what the other one does. I'm not talking about the large manual valve at the top. These are both smaller.
Any thoughts???