That is tough and I don't think there is any good solution. A submersible pond pump will add a little heat to the water but you could always get an external (dry) pump. How are you running the water setup? Are you wrapping tubing around the lines? Up and then back down?
One idea that I had was to blow CO2 from the tap back into the tank. That way once you are done you can empty the lines. Another method would be to get an aquarium chiller. These start around $300 though and not sure how good they are "on demand".
Maybe just freeze your glasses and prepare for a lot of foam the first pour.