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Based on my question in Is a check valve required in California and if yes, where? I do not strictly require a check valve. However, I am reading out my water meter electronically (with a magnetic sensor) and the small backflow causes my readings to be inaccurate. This is not a strictly important thing but I still want to install a check valve to prevent backflow and hence accurate meter readings.

The right way to do, would be to add proper shutoff valves, pressure reducing valves and check valves outside of the house. However, in my old house there is no easy way to do this: All outside pipes are steel and I received quotes in the multiple thousands of dollars ranges. So not an option and plumbing with steel pipes is not DIY-able for me.

However, inside of the house (basement) is copper and I'd like to install a valve in the basement. This will not cover the entire house because because there is a tee before it. But it will be before the water heater which causes the backflow.

Is there any disadvantage to install a backflow preventer instead of a check valve? Or is there any advantage of a check valve?

The price difference ($25 vs $39) is negligible for this project.

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Since you've confirmed that a backflow preventer is not required by local code, you can choose either one.

When a backflow preventer is required by code, that same code usually requires that it be either testable or fail-safe. Testable involves valves and a drain; fail-safe involves a port that spills backed-up water into a pipe or hose upon check valve failure rather than allowing it to enter the water main. These are used on commercial sprinkler systems.

The backflow preventer that you linked to is simply a double check valve that gives more assurance that it's checking the flow. It's like two of the check valve that you linked to, connected in series. The double check valve in the backflow preventer will cause a greater pressure drop than the single check valve.

Since there's no contamination issue or code requirement, you can use the less expensive check valve if you wish.

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