Dewinterizing your RV or trailer is not a difficult task and is a Spring ritual for any RV owners who live in a cold winter climate. If you live in a climate where the winters go below freezing you must winterize your coaches plumbing system. As soon as the fear of freezing temps have passed, it's time to Dewinterize and more importantly, sanitize. Here I concentrate on only the RV plumbing system. You should perform a comprehensive evaluation of all your RVs systems such as propane, generator, appliances, roof seals, etc. Below you can find a great PDF file available to download. The one page checklist is a very good starting point for things to check every Spring.
To start, make sure all faucets are closed. Any water lines you may have disconnected must be reconnected. Leave your water heater in bypass mode. Do not install any house water filters at this point. Connect a water hose to the RVs city water inlet and turn on the water supply. Look and listen for any water that may be dripping.
Once you're confident there are no leaks or pipes that are disconnected you can proceed to flush the RV antifreeze from the plumbing system. Starting with one faucet at a time, turn on the cold water then the hot water. You want the water to run clear at each faucet, shower, toilet, etc. (Don't forget the outside shower and low point drain).
After water has run clear at all faucets, turn the water supply off and disconnect the hose from the city water inlet. Now, fill your fresh water tank with enough water to flush every faucet again. Turn on the RV water pump. Repeat flushing at each faucet as you did when the RV was connected at the city water inlet.
Now it's time to sanitize the fresh water system. Sanitizing is a critical step and should not be overlooked. Failing to properly sanitize the RV fresh water system can lead to illness and even death. Use 1/4 cup of bleach for every 15 gallons of fresh water holding tank capacity. After adding bleach completely fill the fresh water tank with water.
Once again run water at each faucet until you can smell the bleach mixture. After 8 to 12 hours drain the fresh water tank and fill completely with fresh water. Run each faucet till no odor of bleach can be detected. Finally, drain the remaining water from the fresh water tank and you're done. If you still have a bleach odor you can refill the tank and repeat until the odor is gone. You can now install any house water filters and turn the bypass to the water heater off.
I use Camco 40206 TastePURE Drinking Water Freshener every time I fill the RV fresh water tank. I also use a Camco TastePURE 40045 Inline Filter (the blue hose filter) at the spigot as a pre-filter. For the RV house filter, my RV has a 10" canister and I use the Camco 40624 Evo Premium Replacement Water Filter Cartridge. For people who are very sensitive to the odor of bleach you can try Camco 40207 TastePURE Spring Fresh Water System Cleaner and Deodorizer. It is more money than bleach but reviews are positive.