How loud is a hot water heater replacement? Dealing with an extremely anxious cat who just had a urinary blockage

Hi, I know this is probably not a normal post for this subreddit, so I apologize if this isn’t appropriate. My kitty was at the emergency vet last weekend due to a urinary blockage. For those unfamiliar, this can lead to death within 24 hours as being unable to urinate is simply incompatible with life. We have him on prescription food, but one of the other things we are doing is trying to reduce his stress as much as possible. His risk of blocking is highest during the first month as the crystals dissolve, so this is a critical time to keep him as calm as possible.

I guess I’ve just had shit luck this week, because our hot water heater went out a few nights ago. We rent thankfully so we don’t have to worry about the costs. But I am so stressed out about how loud it will be. I’m trying to kind of figure that out now to prepare for how sedated my cat will need to be tbh. My apartment isn’t all that big, I had him in a back bedroom when they came to diagnose today with music playing but he was still so anxious. Thank you in advance