Water Pressure Regulator
The Frugal Choice: Camco 40-50lbs Fixed Regulator
RV water pressure regulators have been independently tested, and these simple little things were found to be among the most reliable at doing their job.
Your First Upgrade: Esright 0-160lbs Adjustable Regulator
This one allows you to set the water pressure coming into your RV at a specific pressure. You might look at the paperwork that came with your RV and find that you can get better water pressure in your shower by dialing it up to 60lbs at the regulator without damaging your water system. Or you might want to conserve hot water, so you want to dial it down to lower pressure. It's often good to have the flexibility to choose your water pressure level.
The Savvy Sweet Setup: Valterra Lead-Free Adjustable RV Regulator
Valterra is a respected company with a reputation for very responsive customer service and warranty replacements, which is the reason a lot of RVers want this model in their water line.