How We Manage Our RV Black & Grey Tanks Full-Time
This is one of those RV articles that doesn't really need pictures. Trust me.
When you're living full-time in an RV, tank maintenance isn't optional. The black and gray tanks are part of the house, and when they aren't happy, neither are you.
We've been living full-time in our motorhome at Bigfoot Trails Basecamp, and over time we've settled into a routine that's pretty simple:
Dump. Flush. Add water. Treat. Repeat.
There are probably a hundred different opinions about the “right” way to take care of RV holding tanks. I'm not claiming this is the only way, or even the best way.
It's simply what we've been doing, and it works for us.
After about a year of full-time use, we've had zero odor problems, no buildup problems that we've encountered, and no ongoing tank issues.
That's good enough for me.
Start With Water
After we finish dumping, I put 3–5 gallons of fresh water back into both tanks.
I don't like leaving them completely dry.
There's no complicated formula behind that number. It's simply the amount we've settled on for our routine, and it gives the tanks some liquid to work with instead of leaving them sitting bone dry between dumps.
It's also consistent with the basic approach recommended by Unique for its liquid RV Digest-It products. Their current instructions call for adding water back to the tank after dumping before treating it.
And that brings us to the part of the system we've relied on the most.
The Backbone: RV Digest-It
The product we've been using is Unique Camping + Marine RV Digest-It, the regular liquid formula.
This has become the backbone of our tank routine.
When we originally wrote this article, our routine was approximately 1 ounce per tank after dumping. That's worth mentioning because the product instructions have changed over time.
Unique's current instructions for regular liquid RV Digest-It call for 2 ounces for tanks up to 40 gallons, with different amounts for larger tanks. They also specify an initial treatment when first starting the product.
So don't use our old 1-ounce number as current manufacturer instructions.
Check the bottle you're using and follow the current directions.
What I can tell you is why we kept using it.
We've used it as part of our normal full-time routine, and after a year of doing that, the tanks have behaved themselves.
That's the kind of product experience I care about.
Not a laboratory test.
Not a manufacturer's claim.
Actual use.
We Treat the Gray Tank Too
The black tank gets all the attention, but the gray tank can get pretty nasty too.
It's getting food particles, grease, soap, hair and everything else that goes down the sinks and shower.
So we treat the gray tank as part of the same routine.
There's nothing complicated about it. After dumping, it gets fresh water and treatment just like the black tank.
Again, the important part for us isn't some magic recipe.
It's doing it consistently.
The Household Mix
Then there's the part of our routine that falls squarely into the category of:
“This is what we do. I'm not telling you that you should do it.”
We've also been using a homemade mix consisting of:
8 ounces of Calgon bath beads
40 ounces of Pine-Sol
Water to fill a gallon jug
After dumping, we'll put roughly 8–12 ounces of that mixture into the black tank.
Does it break everything down?
Hard to say.
Does it help with odor?
Absolutely.
That's about as scientific as I'm willing to get with it.
The important thing is that I don't consider this mixture the thing keeping our tanks healthy. The RV Digest-It is still the workhorse in our routine.
The homemade mix is something we've used because it seems to help with odor.
That's it.
Flushing the Black Tank
After dumping the black tank, I use the motorhome's flush system to backflush it.
I'll start filling the tank and then go inside and add approximately a cup of Dawn dish soap through the toilet.
Then I let the tank fill.
Once it's got plenty of water in it, I let it sit while I move on to the gray tank.
I'm not going to claim Dawn is some magical RV black-tank cleaner.
It's simply something I've incorporated into the routine over time.
The bigger point is that I'm giving the tank a chance to get flushed and rinsed instead of simply opening the valve, watching everything disappear, and calling it maintenance.
While the Black Tank Soaks, We Dump the Gray
While the black tank is filling and soaking, I'll dump the gray tank.
Every other cycle, I'll backflush the gray tank too.
I don't add additional Dawn to the gray tank.
There's already plenty of soap and water going into it during normal use.
Once the gray tank is handled, I go back to the black tank.
The Final Dump
After the black tank has had time to sit, I'll dump it again.
Then I'll dump the gray tank one more time.
That final gray-water dump gives the sewer hose a rinse before we're done.
It's a simple sequence, but it's become automatic for us:
Black → gray → black → gray.
Then we're done.
Until the next time.
What Happened After a Year?
This is really the part I care about.
We've been doing this while living full-time in the motorhome at Basecamp.
After roughly a year:
Zero odor problems
No buildup problems we've encountered
No ongoing tank issues
Consistent performance
That's not a controlled scientific test.
It's one RV, one household, one routine and a year of actual use.
But that's also why I'm comfortable talking about it.
I actually did it.
What We Use
If you want to know exactly what is part of our routine, these are the products we've actually been using:
Unique Camping + Marine RV Digest-It
Our primary tank treatment.
Calgon bath beads
Part of our homemade deodorizing mixture.
Pine-Sol
Also part of that homemade mixture.
Dawn dish soap
Used during our black-tank flush routine.
If you're buying through Amazon, these are the same types of products we're talking about—not a list of ten random RV products I found five minutes ago because they happen to have affiliate links.
That's an important distinction around here.
I don't recommend shit I haven't actually used.
The Bottom Line
There are plenty of ways to maintain an RV's holding tanks.
Some people swear by one product. Somebody else will tell you that product is garbage. Somebody else has a 17-step procedure involving a garden hose, three chemicals and a moon phase.
I'm not getting into that fight.
This is our routine.
We keep water in the tanks, treat them consistently, flush them, and give the black tank a little extra attention when we're dumping.
The backbone of the system for us has been regular RV Digest-It, combined with the flushing routine we've developed over time.
And after a year of full-time RV living, the result has been pretty damn boring.
No smell. No buildup problems. No drama.
That's exactly what I want from an RV tank.
See the Routine
We also put together a short video showing part of the tank-maintenance routine:
