Not sure if this post belongs here, so please direct me if this has been visited in another thread. I have a new 40 gallon Laars indirect fired water heater serviced from a gas fired boiler on its own circulation zone. City water comes into the house (100PSI town pressure - crazy!) and is immediately reduced to 50 PSI with a PRV (which is rececntly been installed too), then goes to a T where it splits off to 1) serve the rest of the houses faucets 2)goes into supply for the Larrs water heater. There are no extra valves or backflow preventers before city water goes into the Laars tank. The hot water out of the tank then splits off and goes to 1st floor kitchen, bathroom and laundry, and 2nd floor bathroom. My issue is that everytime I turn on HOT water in my faucet or shower upstairs, I get pulsing and sputtering. I believe its air in the lines. I've gotten a clear glass and filled it during this event and there are bubbles, not milky white though. If I run the hot water upstairs and wait maybe a half hour, it will happen again. I have ran all my hot water taps and showers in the house for about 10 minutes to try and purge any air collected in the tank, but it has not solved the problem. Lastly, after my boiler runs to heat the tank, I get a small overpressurization in all taps in my house, cold or hot. It's not extreme, but is a noticeably pulse when I turn on the faucet. I think the air in the lines has to do something with the pipes cooling and sucking in air from random shut off valves in the system? Would this cause what I am experiencing? Do I need to install an expansion tank on the city water supply side before my hot water tank? Thanks for the help! A

[color=#1a1a1b]I am needing to move the hot water heater into a space that is shorter than where it currently resides. It will have about six inches of clearance above the tank. So, due to this, I need to move the expansion tank. Can the tank be moved to be on the side of the hot water heater? Attached is how it looks now. [/color]