Hello all.

I have been having some pretty bad hammering in my home when my sprinkler system turns on and am looking for any help I can get at this point. I have talked to local plumbers but I just don't think they get what I am saying and are all telling me to do things that I simply don't think will help... so I came here.

I had a sycamore tree take out my main water line to my house last year and had it replaced. I think it must have been pinched as well from the root system because after I had the line replaced I have been unable to run my sprinklers without first shutting off my water main in my home so that it does not hammer. I don't know if it's technically called a hammer because it's not when the valve closes but my pipes shake and go crazy when the sprinkler system turns on or switches from zone 1 to 2 of 6.

My sprinkler system is tied into my main at the street side and must have a simple T that splits between the home and sprinkler system supply. The sprinkler system does have a double check valve installed on it as well in it's main junction box where they winterize it yearly out at the curb.

I called the local plumbers and asked what would be the best thing to try and fix this situation and they recommended a pressure reduction valve be added to the sprinkler system to try and remedy it. So I had this done a few weeks ago. While they were here they checked the PRV on the home line and everything looked good. I think my in home pressure was 65psi. The sprinkler system line did not have a PRV on it and was pushing nearly 100PSI so they thought that would be the issue. after they installed the PRV on the sprinkler system line it doesn't seem to be as bad as it once was... but it's still there and worries me.

So my question is - is it viable or within code to have a check valve installed on my main water line that supplies my home? It seems that there must be air in the sprinkler lines when the system starts and the rush of water to supply the sprinklers is siphoning from my home line and causing the hammer. I would think a check valve would stop this but I don't know if it's something that could be done. Like I said right now I have to go into the basement and shut off the main while the sprinklers run every day and that keeps the pipes from doing anything when it turns on. just a slightly audible ping is heard when the system turns on and then all is well.

any help is greatly appreciated. this has been a very expensive year so far and I don't want to make things any worse financially. All the plumbers I call say they would replace the double check on the sprinklers first, no matter how much I try and explain the situation I get a blank stare... small town.