Up until 10/15 years ago we put in anti hammer tubes. The *powers that be* found that the tubes got water logged over time. So - it's no longer code. In commercial installs, spring loaded devices are used especially at the end of long runs or at the end of a series of fixtures like urinals. To replace the air in the anti hammers, drain down the water in the whole house with the faucets turned on. The idea is that when you turn the water back on it will compress the air at the highest point at the end of each pipe. That's what the *powers that be* realized that plumbers were not plumbing for - and home owners would not do.