We did an irrigation system install 2 weeks ago. Job went great. Clients loved us and our work. Everything was groovy - like usual. Yesterday, I get a call from the homeowner. He says, "We have a small problem....Apparently, ever since you installed our irrigation system...whenever the irrigation system comes on, our neighbors' pipes start making a lot of noise - rattling and such. The water company installed a device that is supposed to help control that. But it hasn't worked. So we need you to fix the problem." My response, "Ummm.. Ok. So what you're referring to is 'water hammer'. I assume the water company installed a 'water hammer arrestor'. Water hammer is related to having too much water pressure going through their pipes. It's nothing that our company created or had anything to do with......." He responds, "Well, the water company told me that we share the same line or something so what you did to our line effects their water as well." My response, "I think you misunderstood. You guys don't share a mainline with your neighbors. But the entire neighborhood shares the same 'supply line'. And you share some of the water pressure in that supply line." He's a computer geek, so I coninued...."It's sort of like a Cable Modem. Your bandwidth goes down a little as more of your neighbors start using it. In the same sense, whe you use your water, their static water pressure decreases a little." He indicated that he understood that analogy but continued with, "Ok. But they didn't have it before you installed our irrigation system, so you need get this fixed this somehow." My response, "Well, you need to understand that it's not an irrigation contractor's responsibility to fix problems that were already present at neighboring properties. I understand they weren't seeing this effect as much before, but that still doesn't mean we caused it. The problem was always there - waiting to happen. It's a design flaw in their piping. There should probably be a pressure reducer installed or something. But that's not our responsibility." He continued, "Well, we just don't want to cause any problems. So if you could check into it and let us know what you can do...." I agreed that I'd look into it more. I think I'll call their water company and discuss it with them as well. Am I out of line here? I can't see any reason at all how we can be held responsible for this. But at the same time, we survive off of referrals. And these people love us. They've already referred 2 other people to us. I hate to lose them. I also would hate for them to take this any further if I didn't agreee to help (e.g. file a complaint with the contractors board, BBB, etc.) Finally, do you guys know of any device I could install in my client's line that would slow the delivery of water into their system - so as to minimize the water hammer the neighbors are experiencing?