Also, is installation of expansion tanks simple? Could I save money by buying one and installing it myself? If it makes a difference, my house has all PEX tubing for the main piping system.

watts909 backflow preventer4"

I am getting a new water heater installed in my home on Friday (~$1880 including installation and removal of the old tank). The plumber highly recommends also installing an expansion tank, which costs an additional $235. Is the expansion tank something that I really need? It doesn’t cost too much more, but this feels like a classic moment of a naive new homeowner just paying for everything a repair person recommends. I don’t know if my house is a closed loop system - I plan to ask the plumber that question on Friday.

Watts909Spec Sheet

Backflow Preventer Reduced Pressure Zone Assembly With Quarter-Turn Ball Valve And Bronze Strainer, Series/Model: Series LF909M1-QT-S, Nominal Size: 2 IN, Connection Type: MNPT, Pressure Rating: 175 PSI, Temperature Rating: 33 - 140 DEG F, Cast Copper Silicon Alloy Body Material, Seat Material: Celcon® Check, Industry Standards: CSA B64.4 Certified, UPC Listed, ASSE 1013, AWWA C-511-92, FCCCHR Of USC Manual Section 10, IAPMO Certified (UPC), SBCCI, 25-15/16 IN Width, 11-5/8 IN Height, Lead Free: Yes

This 2 IN lead-free reduced pressure zone backflow preventer assembly with its exclusive design incorporating the patented air-in and water-out principle for protection during an emergency condition prevents the flow of polluted water from entering into the potable water supply due to back-siphonage and or backpressure in accordance with national plumbing codes and water authority requirements. Its compact modular design facilitates easy maintenance for in-line repairs without the need of any special tools. It is ideal for protection in continuous pressure piping applications and at cross-connections identified as health hazards and from other contaminants found at the service line entrance. This assembly consists of a lead-free body, quarter turn ball valve shut-offs with lever handles, a strainer, check modules, replaceable seats, top mounted test cocks, and a pressure differential relief valve.

WATTS LF909M1-QT-S Lead Free Cast Copper Silicon Alloy Backflow Preventer Reduced Pressure Zone Assembly With Quarter-Turn Ball Valve And Bronze Strainer, 2 IN, MNPT