The ABCs of RVing Systems

February 1, 1999
Filed under Trailer Gear

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The ABCs of RV Systems

Contrary to popular anthropologic thought, Neanderthal Man just barely predated Tent-Camping Man on the evolutionary timeline. It was only after sufficient pain and suffering  forced the genes to the other side of the pool that RV Man appeared, and life on earth has been better ever since then. But with every leap in the progress of man, there comes a period of adjustment, a necessary interval of learning and refinement. And so it is with that segment of civilization in which RVs reign.

One of the giant steps forward that was made with the appearance of RVs has to do with the onboard systems — those mechanisms that bridge the gap between primitive camping and life at home. Plumbing and electricity and gas appliances all contribute to the comfort and convenience of the user, but they also require some instruction so the operator knows the how and why of operating procedures.

Plumbing System
Technically, the plumbing is divided into two sub-systems: freshwater and wastewater. The freshwater system provides two means for supplying the RV occupants with usable water. One is an on-board freshwater storage tank that allows the RV to carry a ready water supply anywhere it goes. The tank is filled through an inlet on the side of the RV or through the city-water connection controlled by valves. This system incorporates an electric demand-type pump that switches on and off as often as necessary to keep the system pressurized as faucets are opened or the toilet is flushed. The alternate freshwater supply comes from a city-water hookup that delivers pressurized water via a hose that is connected to an inlet on the side of the RV. When camped at a campground that features city-water hookups, simply attach the hose to the inlet, turn on the water, turn off the water pump because it is not needed, and use the plumbing just as you would at home. To protect the RV plumbing system against pressure that is too high, many RVs have a pressure regulator built into the city-water inlet, but if this is not the case, a regulator (available at RV supply outlets) should be installed between the hose and the campground faucet.

A new RV, or one that has been out of action for a while, will have air in the plumbing lines. Purge the air by opening all the faucets in the RV one at a time, both hot and cold, until water flows without sputtering.

The wastewater system is divided into two sectors: gray water and black water. Gray water originates from sinks or the tub/shower. Black water is what is flushed down the toilet. Separate holding tanks store these two types of wastewater until they are ready to be drained at a dump station. Depending upon the type and size of RV, and the number of people using the systems, holding tank capacity will accommodate a certain number of camping days before needing to be dumped. Monitor panels indicate how full the wastewater tanks are, as well as how much water is left in the freshwater tank, allowing the RVer to plan ahead for visiting a dump station and refilling the freshwater tank. These monitor gauges are notoriously inaccurate and should be used for approximation only.

The dumping process is not as difficult as it may seem. Having the right equipment (proper length of dump hose and connections) will make the task easier. Both holding tanks empty through a single outlet located somewhere on the underside of the RV, but each tank is controlled by an individual valve. Connect the dump hose at the RV outlet and at the dump-site inlet. Always empty the black-water tank (generally the larger of the two valves) before dumping the gray-water tank, because in this way the gray water helps flush the dump hose with relatively cleaner water.


4 Responses to “The ABCs of RVing Systems”

  1. Gary Hylton on January 8th, 2013 5:38 am

    I am trying to stop gettin the training DVD’s but I am still getting them
    Please help me with this.



  2. Trailer Life on January 8th, 2013 11:21 am

    Absolutely, Gary – we have removed you from our list. If you have any questions or concerns, please contact us directly toll free at (866) 456-3060 or via email at


  3. David Witherow on February 14th, 2013 1:13 pm

    I am trying to pay on line. I have not found a way to do it. Can you help? does not work.
    Thank you
    Dave Witherow


  4. DENNIS CHAFA on April 3rd, 2013 6:29 pm



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