What is Reddit's opinion of G.A. Murdock Mur-lok 1/4" Quick Connect One Way Check Valve NSF/ANSI 58 Component and NSF/ANSI 372 Lead Free Certified by WQA?

From 3.5 billion Reddit comments

More than likely the buzzing is coming from the inline check valve, not the ASV. https://www.amazon.com/G-Murdock-Mur-lok-Component-Certified/dp/B0756JWQKF

In this case it's not about air moving through the system, it's about the water "squeaking" through the check valve it's pushing open when it's running.

A way to test this is when you hear the buzzing wiggle the tube near the check valve. If the sound warbles then you've found your source.

Thank you for the response.

This is the check valve I am using for both the inlet water line and drain line https://www.amazon.com/dp/B0756JWQKF?ref_=cm_sw_r_cp_ud_dp_PF0QQ28Q3GRBEBTGVFP1. I wanted this at both locations because I run on a well water system with a pressure tank and if I lose power it's possible the RO holding tank pressure will exceed the house water pressure (if someone flushes a toilet or something) causing yet another path of backflow.

Dumb question, but what is the point of the air-gap? Do you think I need both the air-gap device you sent me and the check valve? Could I just use one of these things?