How to Blow Out RV Water Lines with Air

Draining the Water Lines and Tanks

1. How to Blow Out RV Water Lines with Air Picture 1
   Shut off gas and electricity to the water heater a day in advance. The water heater is typically located on the outside of the RV, near the back. It will be underneath an external panel that you can pull open by hand. Check inside the panel for labeled power switches maintaining the electricity and propane supply to the RV. Flip each switch to the off position to give the heater plenty of time to cool down.^[1]

   1. Some RVs have an interior control panel near the front dashboard you can use to deactivate the power supply.
   2. If you don't have time to wait for the heater to cool, run hot water inside the RV. When the water comes out cool, then you can start draining the lines.
   3. If you're unsure about the location of the heater controls, as well as the water tanks and valves, refer to your RV's owner's manual.
2. How to Blow Out RV Water Lines with Air Picture 2
   Open the freshwater tank drain underneath the RV. Walk around the outside of the RV, looking for any exterior panels you can flip open. One of them, usually near the middle of the RV, will have a valve labeled 'city water connection.' Look on the opposite side of the RV from it to find a labeled freshwater inlet valve. Look below the RV for a single drainage valve hanging down. Turn it counterclockwise until fresh water begins flowing from it.^[2]

   1. Some RVs also have low drain point valves nearby. They will be close to the freshwater tank on the side or back end of the RV and labeled. Open them as well to help drain the lines.
   2. The valve can be in other spots, including inside the RV. It depends on the model you have. However, the freshwater always drains out from the bottom of the RV.
3. How to Blow Out RV Water Lines with Air Picture 3
   Locate the black and gray water tank valves on the side of the RV. These valves are typically under the same panel as the freshwater inlet. They are often labeled 'black' and 'gray' and may even have colored handles to make them more recognizable. These valves are used to control the water tanks holding used water inside the RV.^[3]

   1. These tanks, along with their valves, can be positioned elsewhere depending on the RV. They are usually near the back end on the same side as the freshwater tank, but may be accessible through a separate exterior panel.
   2. Keep in mind that some older RV models may not have separate black and gray tanks. The tank drains may also be located underneath the RV.
4. How to Blow Out RV Water Lines with Air Picture 4
   Connect a sewer hose to the black and gray water tanks. After opening the access panel covering the black and gray tank valves, put on some rubber gloves to keep your hands clean. Look for a big drain pipe covered with a twist-off cap. Remove the cap, then attach a 45-degree RV sewer hose joint to it and turn it clockwise to lock it in place. Hook the sewer hose onto the end of the elbow joint and turn it clockwise until it locks in place as well. Connect the opposite end of the hose to a nearby sewer system or septic tank.^[4]

   1. Purchase an RV sewer kit to get all the parts you need to drain the tanks. Kits are available online and at RV centers.
   2. Note that the rules for dumping sewage may vary depending on where you live. Check with your local government for specifics. You can always go to a campground with a dumping point to drain your sewage tanks.
5. How to Blow Out RV Water Lines with Air Picture 5
   Drain the black water tank, followed by the gray one. Pull the black drainage valve toward and watch for water to begin flowing through the hose. Even if the valve lever isn't colored black, it likely will have a label nearby telling you that it is for the black water tank. After the water stops, push the lever back in, then pull out the gray one next to it. Close it up after it has finished draining.^[5]

   1. Always clear out the black water tank first so the gray water washes out any sewage left inside the water line.
   2. If you accidentally open the black water tank first, run water through the lines, such as by flushing the toilet a few times.
6. How to Blow Out RV Water Lines with Air Picture 6
   Disconnect the water supply and turn off the water pump. If your RV is currently connected to a city water supply, detach the connecting hose. Go to the source of the water supply and turn the connecting hose counterclockwise to detach it. Do the same for the end of the hose hooked to the freshwater inlet valve on the side of the RV. Then, flip the nearby water pump control switch to the off position to stop any water flow in the lines.^[6]

   1. The pump switch is typically located next to the heater controls. Check around the kitchen and underneath sinks as well.
   2. You can run the pump for about 15 to 20 seconds to help drain water after opening the valves. However, make sure you shut it off after that so it doesn't get damaged.
7. How to Blow Out RV Water Lines with Air Picture 7
   Open the pressure release valve on the water heater. Go back to the water heater, which is often on one of the back corners of the RV, underneath an access panel. Pull open the panel and locate the metal valve at the top of the heater. Turn it clockwise until water starts spilling out from it. Then, do the same with the big, black plug below the pipes near the bottom part of the heater. Reinstall the plug after water stops coming out of the drain.^[7]

   1. Have a ⁷⁄₈ in (2.2 cm) socket wrench to rotate the plug and pull it out. Some RVs require a ¹⁵⁄₁₆ in (2.4 cm) socket instead.
   2. Expect to see some white sediment come out of the heater. It's ugly and looks like sand, but it's normal. You can insert a hose into the drain to rinse out any sediment left inside the heater.