You never need to empty out or replace the water in your Ergatta rower. It will not evaporate over time. Every six months, you will need to add a water purification tablet to the water. These tablets are provided to you free for a lifetime by WaterRower. Your first batch of water purification tablets will be included with your rower when you receive it. You can request a shipment of water purification tablets from WaterRower at any time.