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Friday, October 30, 2009

Draining, but with Difficulty

I have a Wilderness and the bathtub will not drain properly until I open the sewer valve on the outside of the trailer. Does that mean I may have a vacuum problem with the air vent?
Jerry, (Topeka, KS)

Jerry, it sure sounds like the vent pipe has fallen down into the holding tank below the surface of the liquid in that tank. When you open the termination valve, air is allowed in which quickens the draining of the tub. The bad news; it is usually necessary to drop the tank to properly affix the vent pipe to the tank so this may be a task for a pro.

But first, be sure it has indeed fallen. Remove the vent cap on the roof for that tank; many have caps that twist off. If the 1-1/2” ABS drain pipe is not sticking up above the roof line about one to two inches, then it probably has fallen into the tank. Here's a brief overview of how it's done should you want to tackle this yourself. 

Drain and flush both holding tanks. Disconnect the termination assembly so that the gray water tank can be dropped straight down. Remove the panel below the tub and disconnect the "P" trap and the upper portion of the drain line. Locate the suspect vent pipe inside a closet or lavatory cabinet. Cut the vent pipe as close to the floor as possible using a hacksaw. Use a flashlight and a mirror to view the top of the tank from under the chassis and look for any other drains or vents that may enter the top of that tank. All drain pipes must be cut as close to the floor as possible. 

Remove any electrical wires attached to "well nuts," or probes that connect the monitor panel to the tank. Be sure to mark the exact location for any such wires and to note their respective colors. Locate and determine just how the tank is secured to the underside of the RV. Many installations utilize mounting straps or metal bands that completely support the bottom of the tank. Some may have an upper flange that is bolted or screwed to the underside of the coach. Look over the installation carefully to determine which method was used. 

Support the tank with a floor jack and remove all the supporting hardware and carefully lower the tank to the ground. If the existing fitting for the vent pipe is damaged or if a rubber grommet fitting has been used, install a new fitting which will allow you to insert the vent tube into the fitting yet prohibit further movement down into the tank. Reinstall all components and the tank in the reverse order and insert a length of ABS pipe into the new fitting on top of the tank. You can use a new full-length section or use two shorter pieces and connect them with an ABS coupler somewhere convenient under a cabinet or inside a closet. Fill the tank completely with fresh water to test for leaks anywhere in the system. And don't forget to reinstall the vent cap up on the roof.


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If you are in doubt or do not feel comfortable about a procedure, do not continue. Simply call your local RV service facility and make an appointment with them. The advice, recommendations and procedures offered by the RV Doctor are solely those of Gary. They do not necessarily reflect the opinions, procedures and recommendations of our sponsors or advertisers.