Do you have a lot of old milk jugs or something like that? I would collect a bunch of water from your old house, and store it. As you do water changes at your new house, add half of the old water and half of the new water. Increase the amount of new water you add at every water change until you're only adding new water for your water changes.
You could also do a drip acclimation process. It's along the same lines, but much shorter and you'd need less of your old house's water. Acclimating Fish - Drip Method
This article explains the process rather well.