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We are saddened to announce the passing of Gary Bunzer on April 17, 2020. We hope the RV Doctor website will continue to provide helpful information for you. Thank you for your interest and support for the RV Doctor - Debbie, Heather and Gretchen

Monday, July 11, 2011

Whistling Motorhome and Stopped Up Waste Drains - A Two-fer!

Thanks for a great seminar! Time ran out and I didn't get to ask you two questions. Both are among the more difficult that I've ever had to deal with and I spent eight weeks at and graduated from the Camping World University, so I'm prepared to try most anything. We have a loud whistling noise when traveling over 55 mph; particularly, with a head wind. Of course, the obvious solution (to paraphrase the Henny Youngman joke), "don't drive over 55 mph!" A technician moved the mirrors out saying that it would fix the problem; wrong. Upon returning home I filled in all of the possible openings in the firewall with foam. Do you have any other suggestions? 

Also, equally challenging; I have an occasional blockage of the black water tank at the exit of the drain pipe into the tank. The solution to clearing the blockage is to stick a nozzled hose down there; a messy unpleasant task. All previous coaches have had the toilet positioned directly over the tank. Our floor plan required a double 45-degree angle into the tank. Consequently, solids enter the tank at a slower speed, and the tank depth is less at the entry point than at the rest of the tank. I believe the manufacturer recognized this design shortcoming in our 2008 floor plan by installing a macerating toilet in the comparable 2009 model. I've discontinued using the Sani-Con all together because by emptying fluids first, it merely exacerbates the problem. I had an extension added to the back flush on the tank so that it is now at the position on the tank where the solids exit as opposed to the far left of the tank. Upon returning home, I'll remove the flush and drill a hole in the end. The "nozzles" spray in multiple directions and it should help if I can get a more concentrated spray directly on the solids that accumulate at the entrance to the tank. Any additional suggestions that you may have will be greatly appreciated. Joe G. (no city/state)

Joe, the whistling problem can be a real nuisance and an even more difficult disturbance to troubleshoot. The dynamics of noises produced by moving air is an interesting study. Almost any thing or combination of things can contribute to the noise. The obvious (seemingly) culprits include air horns, TV and radio antennas, curved moldings on sidewalls, design characteristics of the front cap, window placement, etc. This is a tough one to diagnose, especially via long distance! A detailed inspection of everything on the roof and at the front of the coach is in order. Look for loose moldings, gaps in the sidewall, etc. I’ve even seen wind deflectors installed in front of air horns and antennas, but I have no proof that it truly helped. There is a product call Air-Tabs that I have not personally tested or evaluated, but it may be worth a call to the company to see if they have any recommendations regarding air movement and noise at the front of the motorhome. That’s a tough one! You could always just crank up the bluegrass music to 10 and you won't even hear the whistling noise!

As to your second question, it is unfortunate that the toilet drains through two, 45-degree elbows before entering the tank. It is code compliant, by the way, but when coupled with that offset shelf built into the design of the holding tank, it simple worsens the situation. To gain more velocity, always evacuate when the holding tank is nearly full, even if you have to add fresh water to top it off. Refilling the holding tank with fresh water and dumping again will indeed help. In fact, it is recommended to refill and dump all holding tanks in this manner when practical. (Here are my recommended dumping procedures)

And be sure to use an enzyme-based, live bacteria-type holding tank additive to help reduce the mass of the solid waste during the time it's in the holding tank. Using copious amounts of water during each flush of the toilet may help, but it appears you are at the mercy of the floorplan. Unless you opt to replace the toilet with a macerator toilet. 


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