Can a person use a gallon of vinigar a month in a septic tank to get the same results as RideX or other commercial products?

No. Rid-X, and other drain line/ septic system maintainers contain enzymes that literally digest (eat) waste. Vinegar may be good on calcium deposits (like Lyme Away) but pretty useless on drains. You may find a less expensive alternative at a janitorial cleaning supply store. You don't have to do it monthly; but using an enzyme helps making pumping less expensive. My state you have your private septic system cleaned and inspected every three years.
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