Flooded SOB

[davidbrady]

Yes, but isn't it true that water hammer pressure spikes also occur in the absence of air in the line? You have a column of water rushing thru a pipe and a valve is slammed shut. It's an f=ma problem. It's because water is incompressible that the hammer is so hard. Put a column of air at the end and now we've lowered the deceleration and hence the peak pressures; we've given that bullet of water a place to go. I never worried too much about it in a motorhome because the piping branches are typically short, the static pressures low, and the water velocities are low.

Pex can handle static pressures up to 160psi and I'm sure transient pressures quite a bit higher than that, and it has a natural ability to expand so in effect it's acting as a shock absorber to water hammer.