"Drinking seriously changed me as a person - my friends and family were worried and I wasn't a nice person to be around," he said.
"Alcohol is a depressant, a poison and it's really quite sad that it's so culturally ingrained and accepted. Class C drugs do less damage mentally and physically than alcohol."
Since its launch in 2012, the Dry July NZ Trust has raised more than $5.1m through 37,000 partakers, with all funds going to cancer charities.
Farr said while the first couple of days were tough, he will never revert back to excessive drinking again.
"I chose to take part to challenge myself, but to also get my life back on track and for the sake of my health and wellbeing," he said.
"The first two days were challenging, my body was naturally gravitating towards the bottle purely out of habit. But on day three I noticed my creative thoughts came back, I had more energy and my skin cleared up.
"All the positives outweigh the suppressed feelings during and after consuming alcohol." Farr said he'd eventually like to re-form a "healthy relationship" with alcohol, but for now is proud to have raised money for those in need.
"I'd like to not have to rely on it to feel good about myself," he said.