Mr Wilkinson joined the company a year ago from The Wolseley Group and previously spent 12 years with Pace plc and ten years with KPMG.
Mr Knaggs, who has been with the business for four years, began his career as an apprentice with David Brown before gaining experience with Coca Cola and then Macaw and Cott Beverages.
Announcing the appointments, managing director James Cain said: “These are key additions to our board and provide us with a great, all-encompassing skillset.
“Over the last year, Damien has been instrumental in developing our investment strategy for the next stage in our business growth.
“As operations manager, Simon has played a critical role in meeting new business demands, overseen the deployment of state-of-the-art technology and established Harrogate Water as a centre of technical excellence.”
The appointments are made just a few weeks after the business unveiled a £6.5m investment into the firm’s production facility.
The investment programme will increase its capacity by replacing the original glass bottle filling line is with a combination line, which can handle both glass and PET plastic production.