House Calls with the RV Doctor
By Gary Bunzer
July 2005
Dear RV Doctor:
I have a 1986 Real-Lite 27-foot motorhome with a plumbing problem that I have not been able to resolve. When using the water pump while dry camping, I vent water overboard through the city water hookup until the pressure bleeds off after the pump switch has been shut off. There is a separate filler tube for the water tank. I have replaced the water pump, which worked fine, but this has not helped. I have looked for a backflow preventer in the line but can’t find one. After the pump, the water line is teed into a line that carries the water to the sinks and water heater in the rear. Within a foot of the tee but in the other direction is another tee where water comes in from the city water hookup. That line terminates at a drain valve. All of this is located under a dinette seat and above the water tank. This problem started three years ago and has gradually worsened. Any ideas would greatly be appreciated.
Don Glover
Fort Myers, Florida
RV Doctor: Don, it is apparent that the check valve (also known as a backflow preventer) built into the city water inlet no longer seats properly. It may be faulty to the point of replacement, or it simply could have some debris caught in the mechanism. An attempt to reseat the seal can be performed by turning on the water pump, removing the plug from the city water entry, and sticking the eraser end of a pencil into the city water inlet, depressing the spring assembly. Be aware that you might get a little damp, but you also might remove the debris and allow the seat to seal by pressing in on the spring a few times. The pump pressure may be enough to force any contaminants or debris back out the inlet.
If the problem persists, it will be necessary to (a) replace the entire city water entry, or (b) add another in-line backflow preventer at the outlet of the city water inlet. In other words, the new backflow preventer should be installed at some point just after the city water inlet. It’s usually easiest, however, to attach it directly to the back of the inlet. All city water inlets will have a built-in check valve incorporated into their design. The water pump will also have one built into the outlet portion of the pump. A third backflow preventer can/should be installed directly to the cold inlet on the water heater to keep the heated water from migrating back into the cold system. I’ve actually seen an RV that had a cold line teed so close to the water heater inlet (and plumbed to the toilet) that whenever the toilet was flushed, hot water (and steam) emitted from the toilet bowl. I won’t comment further.
Details Of Dewinterizing
Dear RV Doctor:
Last autumn I bought my first RV and had the dealer winterize it after I was done traveling for the year. I want to dewinterize it myself, but I’m not sure of what’s involved. Can I just flush it out to remove the RV antifreeze? Can I obtain a pamphlet somewhere that covers winterizing/dewinterizing?
Peter Stonis
New Kensington, Pennsylvania
RV Doctor: The first thing you’ll want to do is to check the motorhome owners manual for any instructions particular to your unit. Flushing the fresh-water system will rid your coach of RV antifreeze, but there are certainly additional items to check and tasks to perform depending on the extent to which the dealer performed the winterizing precautions last fall. The steps are too numerous to include in this response, but the September 2003 issue of FMC contains an article that provides an in-depth look at all the necessary winterizing procedures (“The Basics Of Winterizing Your Motorhome,” page 60). In addition, the March 2004 issue holds the companion article for dewinterizing your motorhome (“Spring Shakedown,” page 62). Each article details, step by step, the procedures necessary for any motorhome. If you are a member of FMCA or a subscriber to this magazine, you can log on and obtain copies of both articles. To begin, go to www.fmca.com and click on the Technical Articles link in the lower right-hand side of the home page.
Drippin’ Tank
Dear RV Doctor:
I have an older Georgie Boy Cruise Master. My wife and I bought it last year and enjoy it very much. However, I have noticed that the black water tank leaks when it is full. At first I thought it might be cracked, but then I read an article that said the vent pipe may have dropped down. Can you give me an idea of what to look for? If I have to pull the tank, will it be a major undertaking?
Jay D’Auria
Menominee, Michigan
RV Doctor: Jay, it’s quite possible you have a crack at or near the top of that particular tank. A very close inspection is recommended. Sometimes it is possible to crawl under the RV and use a mirror and a flashlight to see the top of the tank, though that is entirely dependent on the exact installation on that model coach. In some instances, frame members may impede your view, or the tank may be positioned flat against the under-flooring. First, drain and flush the tank numerous times (it had to be the black tank, right?), and then begin filling the tank with fresh water. A garden hose into the toilet will probably be the quickest method, though speed is not the point. As the tank nears capacity, closely look with that mirror and flashlight to see exactly where the leak appears first. It’s common to see cracks on the sides of the tank near the top; rarer are cracks on the very top of the tank. It could simply be leaking from around the 3-inch pipe from the toilet or the smaller vent pipe, requiring nothing more than new sealant.
If a vent pipe were to drop, it usually drops into the tank through a rubber tank fitting. This may or may not cause an actual tank leak. You can check the vent pipe from up on the roof. Remove the sewer cap for that vent line and look for the ABS pipe. It should stick up about an inch above the roof. If it is much lower than the roofline or not visible at all, then it may have indeed dropped into the tank. But I digress ….
If it’s not possible to view the top portion of the holding tank from below the motorhome, then, yes, the tank will have to be dropped. It may be suspended by hangers or angle brackets. It’s not a difficult task, though it is time-consuming to remove the holding tank. First, remove the toilet and the floor flange as well as the vent pipe that extends up through the roof. It may be necessary to cut the ABS vent pipe close to the floor line and use a coupler fitting after reinstallation. It is also necessary to remove the 3-inch tank outlet fitting and to disassemble the termination assembly, thereby isolating just that tank. It seems like a lot of work; however, it is simply a matter of logically taking apart a puzzle. After the tank has been removed, reinstall the closed termination valve to block the outlet; support the tank and refill it while on the ground. Soon it will be evident where the leak exists. Or the crack may be quite visible after dropping the tank.
Plastic holding tanks can be successfully welded using a plastic welding machine, but not all repair shops are equipped with a plastic welder, so you may have to shop around. Avoid using an aftermarket patch kit. The only viable method of repairing cracks in plastic tanks is by welding. Patch kits can, however, be used in an emergency situation or for a temporary repair. Keep in mind that some cracks may just not be repairable, i.e. the existence of numerous cracks, deteriorated plastic, impact damage, etc. In those extreme cases, a new tank is in order. Always install the largest possible tank that will safely fit in that same area and will be acceptable given your motorhome’s gross vehicle weight limitations.