This week’s article will cover some plumbing basics related to gray and black water. More specifically, I will discuss how to properly drain holding tanks, as well as some tips on how to deal with blockages.
I have previously covered some of these topics, so some of the information here may be familiar to regular readers of the Coach-Net blog. However, I will restate them in this article for the purposes of topic continuity.
The first issue is the one I have mentioned in articles several times before and has to do with waste dumping. Whenever possible, do not dump the black water (toilet) tank until it is at least two-thirds full. This will ensure maximum suction flow when the valve is opened. This is important because any solid waste stuck to the tank has a better chance of being evacuated when under high flow. Dumping the tank when it has only a little waste in it may result in some waste not being pulled through the outlet. Also, never leave the black tank valve opened during camping. This results in the liquid waste draining while the solid waste will settle on the bottom of the tank. If the solid waste is not rehydrated, it will dry and can easily adhere to the tank floor or walls. This often results in having to vigorously flush the black tank. There have been many occasions where I have had to perform major repairs to holding tank systems due to accumulated solid waste. It is not a pretty job and can be expensive, especially if removal of plumbing components or tanks is involved. Always drain the black water first, then the gray water. This allows the gray water to flush the black water from the sewer hose, making rinsing a much more pleasant job.
As alluded to above, RV waste water or sewage blockages can be a nightmare at worst and an inconvenience at best. The easiest way to avoid dealing with blockages is to prevent them from occurring in the first place by following some basic pointers. First, do not flush anything other than RV-rated tissue down the toilet. You can extend this list to anything rated for septic systems, but generally, this should be single-ply tissue. There are some articles that discuss whether certain name-brand higher ply tissues are safe for RV use. I tend to avoid any risk of tissue blockages by sticking with single-ply. Same goes for the sinks, avoid washing anything solid down sink drains, and never pour cooking oil or grease into sinks or toilets.
If your RV doesn’t have a black tank flushing attachment, I recommend installing one if possible. However, since this requires drilling through the tank, these must be professionally and/or properly installed to avoid leaks. Use the flusher to keep the tank clean. Be sure to use a separate garden hose and not the fresh water hose used for potable water. If you don’t have a flushing connection, I recommend purchasing a flushing wand.
If you do encounter a blockage in your rig, most can be cleared using standard household methods such as drain cleaner. However, be sure to use a cleaner that is rated safe for septic systems. For sink blockages, you may have to remove P-traps to access a blockage. In the case of toilets, a stick or toilet snake can be used, but be careful not do damage seals and other sensitive plumbing components.
In the case of a persistent blockage, seek help from a professional RV repair facility as soon as possible.
About the Author:
Steve Froese, an avid RV owner, traveler, and Coach-Net member since 2013, is the principal of “A Word to the Wise Technical Communications”, a published RV author, certified RV technician, and licensed Professional Engineer. He frequently collaborates with the “RV Doctor”, Gary Bunzer, and has worked with the RVIA/RVDA as a technical and training writer and consultant. Professionally, he works as a quality engineer and musician. Watch for more of Steve’s work in upcoming Coach-Net publications.
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We eliminate all possibility of blockage by putting a small wastebasket next to the toilet and placing all paper, wipes, etc. in the waste can. We started doing this with our first trailer 14 years ago and have never had an issue. The offending waste is placed in the regular trash bag and walked up to the dumpster.
When flushing Toilets getting a noise sounds like a vent. How can this be fixed
Minnie Scott said:
You are very intelligent to deal with blockatges, very basic but something we are usually forgot. Thanks for this useful tips here
Dave and Dayna said:
We also back flush the black tank with the grey tank. This is done by lifting the sewer hose above the height of the tanks, allowing the grey water to flood the black tank, after you notice the flow start to slow down close the grey valve and let the black tank evacuate, (do this after the black tank is empty) .we are able to back flush at least 4 times if the grey tank is full…i am always amazed the amount of stuff that still comes out , even after the tank cleaner system has been running for 5 to 10 minutes.
Thanks so much, was always curious about this, i’m looking into purchasing a new rv soon