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Every spring when I open the valve to restart the irrigation system after it was wintereized, I have to open it partially and wait a while before opening it further because severe water hammer develops and it sounds like something is going to break! I close the valve (looks like 3/4" or 1" line, by the way) until the water hammer stops, then try opening it a little again and repeat. I stay nearby the shutoff valve until I am sure the banging will not resume.

Usually after a matter of minutes, the underground plumbing is filled and the water flow and noise stop. There is a water meter in the basement below the valve with a rotating vane and I can see it slow down...eventually.

My question is about how long it should take and how to tell if there is a problem. Last year the Febco device wouldn't stop leaking and I bought a replacement parts kit (poppet and whatever). There is typically some water flowing onto the ground outside but it normally stops when the system is 'full'.

It always seems to take a disturbingly long time to 'fill' the system. I recall always feeling like something must be wrong due to how long it takes. (only 4 stations and maybe 1/6 acre yard at most).

Last night I decided the water flow was not slowing down at all and I couldn't get rid of the hammering for very long. I ended up closing the shutoff valve and postponing the startup.

How long is reasonable and what is actually normal? In my mind I think that what normally happens is pressure must build up or decrease once all the lines are filled, and the Febco device then closes - maybe it's like a check valve or similar.

Thanks for reading this far, and for any advice.

Murray
Holland MI

OK, thanks Mr. Boots.

Before reading your response I went out & looked (during the day, this time) at the 765-1 and out of curiosity shut off the output valve between the 765-1 and the underground pipes to see what would happen. I had the supply valve open just enough to have some flow but no hammer. After closing the out put valve, the water leaking out of the top of the 765-1 stopped after several seconds. I decided this probably indicated the 765-1 was working properly (shutting off with back pressure) but wasn't very significant because I still obviously needed the output valve open.

The water's been running, at reduced flow to avoid hammering, probably 20 minutes now...that just seems too long to me. I'll go shut off the output valve & see how things act.

Thanks