I've never had an issue with water hammer in my house until a couple months ago. The fill valve on our newer LG washer went bad. Because we had the extended warranty I just called the company and they sent a tech. He confirmed it was the fill valve and replaced it the next day. Ever since that part was replaced we now have a water hammer problem at the washer. I think it's just the cold line. I thought maybe the water line valve was open too far so I closed it a few turns. The hammering isn't as severe now but it's still there. It also hammers when I go to shut the water line off (turn type valve, not a ball valve) completely, which it never did until after he installed the new fill valve on the washer. I also turned back the water line valve to the whole house just a little thinking maybe the water pressure was too high. Don't know if that would do anything or not. I bought a water hammer arrester that just screws onto the water line behind the washing machine but I haven't installed it yet. Just wondered if anyone knew what would cause the hammering to start after replacing that part, or if it's just a big coincidence. I don't know much about water hammer, this is the first time I've had to deal with it. Thanks in advance for any input.