What every RVer should know about RV Wastewater and Holding Tanks (AKA the sh**ty part of RVing)

What every RVer should know about RV Wastewater and Holding Tanks (AKA the sh**ty part of RVing)

Most items inside an RV operate very much like a normal house. The same is true for your RV toilet, sinks and shower- except the water and waste doesn’t just simply “disappear” like they do at home. Holding and dumping wastewater can be one of the more intimidating chores of owning an RV, and since dealing with wastewater has its dangers, care must be taken to prevent problems, avoid odors, and protect yourself from disease. By understanding how the systems work, and the best practices for operation, you will be able to handle the RV wastewater storage safely, confidently and problem-free. 


What components make up the wastewater system in an RV?

Most wastewater systems contain gravity flow (non-pressurized) piping systems for both the sink and toilet water. The common components are: sink traps, ABS piping, toilet flange and piping, a grey water holding tank (for sink and shower water), a black water holding tank (for toilet water) and a set of gate valves used for dumping the tanks.


How many wastewater storage tanks are on an RV? 

Typically there are two tanks- one for holding the sink and shower water, and one for holding the toilet water. Some larger RV’s may have additional holding tanks.


What types of toilets are in an RV?

The majority of RV toilets have a simple gravity-flow operation. Unlike a household toilet, they do not have a tank of water that is used for flushing. Instead, they use a water valve that uses pressurized water to flush whenever the hand or foot lever is pressed. At the same time, a slide valve in the bottom of the toilet bowl is opened to evacuate the contents. Some RV toilets are electric and use 12v pumps to provide water for flushing, and some toilets contain a built-in macerator pump that is used to grind and pump waste as it exits the toilet. 




Why do I need two holding tanks for RV wastewater?

RV’s are designed with separate holding tanks for several reasons: We tend to use much more grey water in the RV due to the volume of water needed for a  shower. Having separate tanks allows you to dump the grey water without needing to dump and re-treat the black water tank with toilet chemicals. Also, by having a store of grey water held in the tank, it can be used to rinse the sewer hose after the black toilet water has been dumped.


Why can’t I leave the RV holding tank gate valves open while I’m hooked up at the campsite?

Leaving the grey tank valve open while camping will not cause any issues, aside from the possibility of insects entering your RV tank from the campground sewer system. Problems can arise, however, when the black water tank gate valve is left open, due to solids landing and staying inside the tank when the toilet is flushed, while any liquids run out. This can cause the solids to build up and eventually create a clog that will require servicing to remove. It’s best to avoid this messy situation!


What is the best practice for preparing my RV toilet wastewater tank for use?

Make sure the sewer gate valve is fully closed on the exterior of the RV. Add water to the toilet bowl and then add the proper amount of toilet chemical (as directed) to the toilet. Flush the toilet allowing several gallons of water to the tank to mix the chemical and provide a liquid “base” to the holding tank to help avoid any solids from forming in the tank.


What’s the best procedure for emptying my RV holding tanks?

  1. Put on some disposable RV dump gloves. 2) Make sure the gate valves are completely closed by pushing the handle in tightly. 3) Carefully remove the termination cap (Note- some wastewater may be present if the valves were not closed properly or if the valve seals need to be replaced). 4) Carefully attach the sewer hose adapter end to the lugs on the termination fitting. 5) Attach the other end of the sewer hose to the sewer dump location, making sure that it is secure (it’s always a good idea to add weight on top of the fitting to prevent the end from coming out while dumping). 6) Open the black water gate valve slowly until fully open while watching to make sure there are no leaks in the hose or fittings, and allow black tank to fully drain 8) Run fresh water into the toilet until water coming from the tank runs clear (use a clear sewer hose adapter at before or after the sewer hose for verification). 9) Fully close the black water gate valve. 10) Slowly open the grey water gate valve and allow the grey tank to fully drain. 11) Run fresh water in the sink or shower to rinse the grey tank. 12) Fully close the grey water gate valve. 13) Disconnect the sewer hose from the RV termination fitting keeping the end raised. 14) Using a water hose, add fresh water to the sewer hose and rinse thoroughly (being careful not to allow the water hose end to come in contact with the sewer hose and possibly transfer bacteria). 15) Drain the sewer hose by lifting the RV end until it is empty and properly store the hose. 16) Dispose of gloves and wash hands thoroughly. 

Use these tips and you’ll make your worst RV task a whole lot easier! Should you have any questions about this or any other task with your RV, contact one of our helpful experts at www.onesourcerv.com

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