Things I have done:
- Replaced faucet, and its shut off valves
- Put new shower cartridge (OEM)
Water is coming from the city supply, not well. This issue started happening for the past three weeks and I lived in the house for two years.
When I start the shower (hot water only OR mixing cold water), OR start faucet (hot water only OR mixing cold water) the pressure of hot water suddenly goes down and pipes start banging.
Note I do not run shower or faucet at the same time. This happens sporadically, not consistently, but very frequently. No banging noise or issues in the kitchen. Hot water is supplied by standard hot water heater bought from Home Depot. There are no arrestors in either shower, faucet, or kitchen and never been any.
When I replaced cartridge/faucet, issue went away for 5 days. It came back today after I took a long shower (?)
The noise is super loud and I'm afraid that the banging will literary rip off one of the connections somewhere.
*****UPDATE 12/13 - solution *****
I noticed there was a rust in the faucet aerator when I unscrewed it, and it was a brand new faucet. This prompted me to look at the pipes leading from hot water heater to the shower-- and found few feet line of galvanized pipe (I think that is how it is called?) (along with corroded unnecessary shut off valve in there) connected to the copper. I'm thinking the rust came from that pipe so water was not evenly flowing thus causing the pulse...
I replaced that few feet old pipe run with pex and it solved it! No more pipe banging for the past couple days and flow of the water is even and smooth. Thank you everyone for your input. Hopefully this post will help someone in the future.
I still need to deal with the pressure tank tiny leak but this issue has been solved.