Guns, is this the same water that was in it when you moved in? If so, you need to be careful about chemical saturation. I forget the PPM (parts per million) level you need to be below, but a good test kit or EC (electrical conductivity) meter will tell you. If you break that level your chemicals will lose effectiveness and you will have to change the water.
BTW, when it comes time to refill, a large magnet placed directly on top of your water meter will stop your meter from turning. Just make sure you remove it after you're finished. The city seems to dislike this practice.
