For seventy years, Charmin has been testing the biodegradability of their toilet paper products in septic tanks. Charmin states directly in the FAQ on their website (see Reference 1) that their toilet paper will settle and biodegrade properly in a regularly maintained and fully functioning septic system.

On the Other: Other Tissue May Break Down More Easily

Charmin toilet paper is thicker than basic bargain toilet paper and contains no recycled paper, meaning it may take longer for it to break down in your septic system. Consumer Reports singles out Charmin Ultra-Strong as being particularly slow to disintegrate (see Reference 3). Bargain toilet papers, and toilet paper made from recycled paper products will break down in your system faster, creating less chance of back up.

Bottom Line

Charmin offers their guarantee right on the packaging that their toilet tissue is septic safe, and provides video evidence of their testing measures on their website. If you are still uncomfortable because you have an older system, or have had back up problems in the past, it may be best to go with a bargain brand, or one made from recycled paper products.

Source:

Charmin Toilet Paper: Frequently Asked Questions

InspectAPedia: Septic Tank Maintenance

Consumer Reports: Toilet Paper