We are quite flexible with our warranty coverage on cards. Absolutely, you can water-cool your card with us and it will not void your warranty. As a friendly reminder, be sure to keep all associated parts for your original factory cooler, such as thermal pads, screws, and the heat-sink fan. In the event you need to exercise your warranty on your card, you will need to have the card reverted back to the original factory condition. Good luck in your water-cooling setup!