Go to your local Walmart or RV store and but a blow out Schrader valve.
Use an air compressor to blow out your lines. Attach compressor to city water inlet. Apply about 40-50 pounds of air to system. Open each of the faucets one at a time. Don't forget to operate the toilet valve.
Then remove drain plug or anode from water heater. Allow water to drain. Inspect anode if equipped and replace if needed. This is a good time to replace the nylon drain plug if equipped.
Drain holding tanks.