Your RV’s black and gray tank maintenance isn’t exactly the glamorous side of RV ownership, but taking care of your holding tanks properly can make a big difference in how well your plumbing system works.
Most tank problems don’t happen overnight. Clogs, odors, inaccurate tank sensors and slow drainage are often the result of everyday habits that allow waste and residue to build up over time.
The good news is that RV tank maintenance doesn’t have to be complicated. A few simple habits can go a long way toward keeping both your black and gray tanks working properly.
Know the Difference Between Your Black and Gray Tanks
Your black tank collects waste and water from the toilet.
Your gray tank collects wastewater from sinks and showers. Depending on the RV, you may have more than one gray tank.
Because the tanks collect very different things, they need slightly different care. But they have one important thing in common: water and good drainage practices are essential.
Keep Your Black Tank Valve Closed
If your RV is connected to a sewer hookup, it can be tempting to leave the black tank valve open all the time.
Don’t.
When the valve is left open, liquid can continuously drain out while solid waste and toilet paper remain behind. Over time, that material can dry and accumulate on the bottom of the tank, creating what RV owners commonly call a poop pyramid.
Yes, that’s really what it’s called. And no, you don’t want one.
Keep the black tank valve closed and allow the tank to fill before dumping it. The volume of liquid in the tank helps carry solid waste out when the valve is opened.
Use Plenty of Water
One of the simplest things you can do for your black tank is also one of the most important: use enough water when you flush.
Trying to conserve too much water can actually create problems. Solid waste and toilet paper need enough liquid to remain suspended and move through the tank when it is emptied.
After dumping and flushing your black tank, add some water back into the tank rather than leaving it completely dry. That gives new waste and toilet paper somewhere to go instead of allowing it to sit on a dry tank surface.
Don’t Dump the Black Tank Too Soon
A nearly empty black tank doesn’t have much force behind it when you open the valve.
Whenever possible, wait until the tank is around two-thirds full or more before dumping. If you need to dump before the tank is sufficiently full, add water first.
More liquid means a stronger rush through the drain line, which helps carry solids and toilet paper out with it.
Dump the Black Tank Before the Gray Tank
When it’s time to empty your tanks, dump the black tank first.
Once it has finished draining, close the black valve and dump the gray tank. The gray water flowing through the sewer hose helps rinse away some of the residue left behind from the black tank.
It’s a simple habit, but it makes dealing with the sewer hose a little less unpleasant.
Flush Your Black Tank Regularly
Many RVs have a built-in black tank flush connection that sprays water inside the tank to help remove remaining waste and buildup.
Use it periodically, especially after dumping a fuller tank.
If you’re using the tank flush while the black valve is closed, stay right there and monitor it. Never turn on the water and walk away.
An overfilled black tank can force wastewater where you definitely don’t want it going.
Tank Treatments Help, but They Aren’t a Substitute for Good Habits
Black tank treatments can help control odors and may assist with breaking down waste and toilet paper.
What they can’t do is make up for poor tank maintenance.
No chemical treatment replaces adequate water, proper flushing and allowing enough liquid to accumulate before dumping.
Think of tank treatment as part of your maintenance routine, not the entire routine.
You May Not Need Special RV Toilet Paper
You don’t necessarily have to buy toilet paper labeled specifically for RVs.
What’s important is that the toilet paper breaks apart readily in water.
There’s an easy way to test yours. Put a few sheets in a jar with water, close the lid and shake it. If the paper quickly begins breaking apart, it’s generally much less likely to contribute to buildup inside the tank than a thick paper that stays intact.
And regardless of what the package says, never put wipes down an RV toilet, including wipes labeled “flushable.”
Your RV plumbing system is not the place to test how optimistic that label really is.
Don’t Forget About Your Gray Tank
Black tanks get most of the attention, but gray tanks can get pretty nasty too.
Soap residue, body oils, hair, food particles and grease can accumulate inside the tank and drain lines. Eventually, that buildup can contribute to odors and slow drainage.
Avoid pouring cooking grease or oil down the kitchen sink. Wipe greasy pans and dishes before washing them whenever possible, and use sink strainers to catch food particles before they enter the plumbing system.
Periodically allowing the gray tank to accumulate a good amount of water before dumping can also help move debris through the tank and drain line.
Should You Leave the Gray Tank Valve Open?
For RV owners staying on full hookups, leaving the gray valve open may seem convenient because shower and sink water simply drains away.
But leaving it open continuously can allow residue to remain behind rather than being carried out by a larger volume of water.
A better routine is to periodically close the gray valve and allow the tank to fill before dumping it.
Many RV owners also close the gray valve before they’re ready to dump the black tank. That gives them a tank of gray water to run through the sewer hose after the black tank has been emptied.
Be Careful What Goes Down Your Drains
Your RV holding tanks aren’t designed to handle everything a residential plumbing system might tolerate.
Keep these out of your tanks whenever possible:
- Cooking grease and oils
- Paper towels
- Baby wipes and cleaning wipes
- Feminine hygiene products
- Cotton swabs and cotton balls
- Large amounts of food debris
- Harsh or inappropriate chemicals
The less unnecessary material that enters your holding tanks, the less opportunity there is for buildup and clogs.
When Your Tank Sensors Don’t Tell the Truth
You dump the tank, check the monitor panel and it still says one-third or two-thirds full.
Sound familiar?
Tank level sensors are notorious for inaccurate readings. Waste, toilet paper, grease and other residue can stick to the sensors inside the tank and cause a false reading.
A tank that shows partially full immediately after being thoroughly emptied may not actually contain that much liquid. The sensors may simply need cleaning.
However, don’t automatically assume every inaccurate reading is a dirty sensor. If the tank isn’t draining normally or you’re experiencing other plumbing problems, there could be another issue that needs to be investigated.
Stationary RV Owners Need a Tank Routine Too
If you live in your RV full-time or stay connected to the same sewer hookup for months at a time, it’s especially easy to fall into an “everything stays connected” routine.
Your sewer hose or permanent sewer connection may stay hooked up, but your tanks still need to fill and empty properly.
Keep the black valve closed between dumps. Use plenty of water. Periodically allow your gray tank to fill before emptying it. Flush the black tank regularly, and pay attention to changes in drainage or odors.
Being permanently connected to sewer doesn’t turn your RV holding tanks into residential plumbing.
They still need to be managed like RV holding tanks.
When It’s More Than Routine Maintenance
Persistent odors, recurring clogs, a tank that won’t drain properly or wastewater backing up aren’t problems you should simply keep treating with more chemicals.
You may be dealing with hardened waste buildup, a blocked drain line, a problem with a dump valve, damaged plumbing or another issue that needs to be properly diagnosed.
And this is one area where guessing can get unpleasant very quickly.
Good tank habits can prevent many common problems, but when something isn’t working the way it should, figuring out why is the first step toward fixing it correctly.
A Little Routine Goes a Long Way
Taking care of your RV’s black and gray tanks isn’t complicated.
Use plenty of water. Keep the black valve closed between dumps. Let the tank get sufficiently full before emptying it. Flush it regularly. Keep grease, wipes and other inappropriate materials out of the system, and don’t forget that your gray tank needs attention too.
Your holding tanks may be out of sight, but they definitely shouldn’t be out of mind.
Because when an RV tank decides it wants your attention, it usually has a pretty effective way of getting it.
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