RV Holding Tank Maintenance

How to keep RV tanks clean and clog-free

While this article focuses on the black tank which contains the toilet waste, all the tanks need to follow the same procedures at least occasionally. More on that later.

We have learned a lot about RV holding tank maintenance – and not always the easy way! Taking precautions so that your toilet doesn’t back up and knowing how to possibly resolve it if it does is valuable information. RV repair shops don’t generally want to mess around with unplugging your black tank, and if your rig is older a replacement tank that fits might not be available so it could be expensive to retrofit a different tank into your rig. Don’t take shortcuts, and that includes trying to “save” water.

Understanding RV Plumbing Systems – About RV Holding Tanks

The first thing is to understand that your toilet and black water holding tank is neither a fixed-in-a-building (like residential) toilet nor a septic system. The differences between your RV toilet and a “residential” one is obviously that with the RV you don’t flush directly into a sewer system where there is usually a lot of 4” pipe that drops down and away from the toilet and building into a larger drainage system, and a residential toilet flushes at least a gallon at a time, usually more—as much as 5 gallons! And once the toilet waste gets into the main line of a residential system there is usually a LOT of water that pushes it out into the main sewer system from every other place in the building where water comes from.

Your RV toilet is not like a septic system either; this is very important because most people think that it is exactly like a septic system. In a septic system, your waste discharge goes into a holding tank or very large pipes that are the same as a tank. The holding tank has baffles so that the solids don’t go directly out to the drain field but instead settle to the bottom, with the fluids running over the top of the baffles into the drainage field plumbing. And the BIG difference is that with a septic system is the holding tank needs to have the sludge that settles to the bottom pumped out periodically, anywhere from every 1 to 3 years. If there is sludge in your RV black water holding tank, you don’t have a service company that can pump that out! And the commonly advertised chemicals that say they break down solid waste don’t actually dissolve them into water, which is what their advertising makes it sound like they do… they can’t create water out of solids, just mostly make smaller particles. And the enzymes and biolife in some products advertised to “break” down solids can also become an actual part of the sludge. It’s kind of like yeast, in that the yeast in a baking or brewing application would eat the sugars but the live yeast dies and their bodies become part of a sludge, along with any other byproducts they create by “eating” the “food”.

Refer to the sketch below. This is to give you an idea how an RV black tank is constructed. Of course, you don’t know exactly how yours is constructed, but this gives you a good idea. The plumbing pipe from your toilet is either a double-elbow or a straight pipe. In the double elbow, solids can accumulate in the pipe, and since after you flush if anything is sitting in there it will dry out quickly and stick, starting a buildup. Therefore, not flushing enough water leaves solids sitting there that dry rapidly into a sticky mess. At the bottom of the tank, under where the pipe from the toilet drops, this is where the infamous “poop pyramid” can form. Of course, it includes paper. Without proper cleaning this can grow into a mound that reaches the bottom of the pipe from the toilet. As far as your flush kit goes, you have no way of knowing where the spray from the flush kit hits the tank and how far back it reaches, and if it hits the corners. Without enough water, solids can build up on the entire bottom and around the bit of flange where the drain pipe is as well. I show the sensors as a guess. Sensors that “short circuit” because solids remain on them will read inaccurately.
Given these differences, your RV holding tank maintenance also has to differ from regular plumbing maintenance you are used to in a residence.

Macerators

Have a macerator? For those that don’t know what this, it is a grinding type device similar to a garbage disposal that grinds the solids up into very small particles. There are some that go between the toilet and the black tank and those that go after the black tank to pump everything out in smaller bits. While there are reasons why you might want or need this (pumping uphill for example), the problem is that in systems where the macerator goes between the toilet and the tank this can just cause stickier particles to be created. For macerators that are located after the black tank, its pump sucks stuff out, but the issue there is that the liquids will pump out quicker than solids so that solids may be left hanging around in the tank. The point here is that if you have a macerator, don’t think that you have a great solution already in place to keep your black tank cleaned out properly. In fact, you might be making things worse. You need to follow these clean out processes just as if the macerator didn’t exist, and in fact might need to be even more careful (repeat more of the flushing steps). Remember to never run a macerator pump “dry”, it can burn out the pump motor.

Keeping the RV black tank clean

What RV holding tank maintenance products should you use? There are many commercial products on the market that advertise they digest all the solids. However, these chemicals and bio-critters just change the solids into a sludge, which can sit there and form into a solid lump and cause blockage, especially in the pipes and especially if you have elbow plumbing from your toilet into your black tank. I wrote about this above when describing the difference between an RV black tank and a septic system. Instead, there are many articles on the internet now that talk about the “GEO Method”, which actually was invented some time ago. I am using one that a company called KleenTank writes about. Pine Sol or generic equivalent with Calgon bath beads is the ingredients they describe, mixed in water. There are others. That formula uses 40 ounces of Pine sol or equivalent mixed with 8 ounces of Calgon Bath Beads into a gallon jug with the remainder filled up with water. Along with the action of being like a water softener, it disinfects and deodorizes. I mix it up in a gallon plastic jug and keep it in the bathroom. Essentially, these GEO methods create a more slippery surface so that nothing sticks to the plumbing or tank and when you drain your black tank, everything goes out in a form closer to the way it went in, albeit with a lot of separation into tinier bits, etc.

I have a theory that because these various GEO Method formulas have differences, alternating between them may give you the best overall outcome. I stick with my Pine Sol-Calgon version most of the time when flushing.

Other GEO Method formulas you’ll find are one using just Dawn dish soap liquid (1/4 to 1/3 cup), or one cup of Dawn to a almost full tank as you begin driving to a new location, and another formula uses the following: 2 Capfuls Of Liquid Water Softener (like Calgon), 1 Cup of Dawn dish soap and 1 Scoop Of Borax Powder (Borax is optional, but add a gallon of preferably hot water first to dilute the Borax).

Using water as part of RV holding tank maintenance

RV Toilet operation and using your system—think how much water is flushed when you use a toilet in your home or anywhere else. The least is about 1.5 gallons and as much as 5-7 gallons! Lift the cover off your toilet tank and flush and just see how much water goes down in one flush! That’s to try and insure all the solids get flushed down into the main line. Don’t try to conserve water with a meager flush that includes solids. Give it at least a slow 5 count while flushing, and don’t be afraid to go longer, especially if you used a lot of paper. Paper is the worst clogger! You’ll be a lot better off dumping your tanks more often than having to deal with a blocked toilet system.

Best toilet paper for RV tanks

What kind / brand of toilet paper is best for keeping RV tanks clean and clear? You can search on YouTube for people testing toilet paper for RV use. The video I liked most was done by a couple whose channel is called “Wandering Weekends” on YouTube – see their video “RV/ Marine Toilet Paper… Is It Necessary?? Surprising Results”. They do a good job of comparing products that are specified as “RV specific” with many others and the results are indeed surprising. Their testing caused them to switch brands and it did for me too! Saved some money as well. From their testing, interestingly, the more expensive brands sold by camping companies and the like as being “RV specific” don’t seem to be the best choices!

Tip–Use the campgrounds bathrooms as much as possible for doing Number Two… Minimizing the amount of solids, especially paper, going in to the tank. Never put any kind of paper except RV (septic approved or tested for RV toilets) toilet paper down the toilet. NEVER!

Tip–This is kind of gross but if you suspect you are developing a backed up toilet situation it is less gross to handle it right away than waiting until it becomes worse. A solution would be to bring a bag into the bathroom with you and dispose of your paper in the bag and not flush it down. Note that if you are boon docking* (dry camping) this would help you save water too. Just pointing out that (in my opinion) it’s less gross than changing a baby’s diaper or cleaning up after your dog, or scooping out a kitty litter box. Just sayin’. *More about boon docking here.

RV Holding Tank Maintenance Do’s & Don’ts

First thing—NEVER leave your black tank valve for emptying the tank open while you are camping. Leaving the valve open when you are connected to a sewer dump at a campsite drains all the liquids out as they come in and the solids stay in the tank, gather, harden and stick to plumbing and tank, and usually most of it in one spot. If you leave it open, you’ll have a plugged system in no time!

Second thing—always keep 10% of the total volume of your blank tank in there. So after dumping and flushing, make sure you have that amount in there as your last step. If you don’t know how much your black tank can hold, estimate it at least 50% of your fresh water tank. More is better! But if you don’t capacities, at least 1 gallon is small rigs up to 2.5 gallons as the size of the rig increases.

Third thing– Fill up your black tank to about 2/3 before you travel, as long as you know you’ll be able to dump at your destination. Some extra GEO solution is good too. Let that slosh around for your trip and that can help clean things up. Dump always when you arrive at a destination (and perform a flushing procedure) because that tank gets churned up pretty good while driving. Even after doing the flushing process before you leave for your next destination and seeing clean water come out you will usually be shocked as to how much stuff comes out when you dump when you arrive.

RV Holding Tank Dump & Flush Procedures

If we are going to be at a campground (with sewer connection) long enough that I’ll be dumping tanks several times while there, I connect a ‘Y’ fitting where the two output connections have separate shut-off valves. One side of the ‘Y’ goes to the fresh water intake and the other goes to the flush kit attachment. This way I don’t have to be disconnecting and reconnecting different hoses to do a dump-and-flush operation. By the way, always use a separate hose dedicated to flushing your blank tank and never use it for fresh water. You could also obtain a back-flow preventor and connect it between the sites water connection and your flush hose—that will really prevent anything from backing up!

And don’t rely on your system’s tank gauges to tell you when things are empty or how much they contain. They are notoriously inaccurate. Use them as a guide but to be safe think of them as reporting less than what is actually in the tanks. That will keep you safe from an overflow. You’ll know you have a bad sensor when it reads empty and you know you have several gallons in the tank.

Before you start the dump-and-flush procedure, of course, make sure your flushing hose is “airtight” to the dump plumbing. I recommend that you have a clear component coming out of your drain into your hose. I prefer one that has an elbow (angle) on it, but I have a straight one as well because sometimes there is uneven ground and you can’t use the elbow. This allows you to see what is coming out of the tank. This is important because this is how you know everything you can get out is out, and you learn what it takes to get your system clean by repetitive flush operations to get to just clean water coming out.

RV Holding Tank Dump And Flush Procedure

1. Attach you water hose used for flushing to the system’s tank flush. It should be on the side by the blank tank labelled “flush kit” or something similar. It is a standard garden hose connection. If your rig doesn’t have one get a component that goes between your rig and the drain hose that has a garden hose type connection for flushing. I use a different hose than my fresh water hose, for the obvious reason that I don’t want to take any chance of contamination. If your rig doesn’t have the flush connection built in, use the one on the component I mentioned above, it’s better than nothing.
2. Open the black holding tank drain valve. Let it drain by itself (don’t open other tank valves).
3. After the blank tank is mostly done emptying, run the flusher line until water comes out clear. Shut the water off.
4. Take a bucket with water (preferably hot), fill up a gallon or two and dump it into the toilet (flush valve lid open of course) as quick as possible.
5. Run the outside flush hose again and see what comes out.
6. Repeat steps 3 through 5 until the water comes out clear and solids free. Yes, that seems like a lot of water, but overall it is less than the water you use flushing toilets in a residence and after all, do you want to take any chances that your system gets clogged?
7. Once things are clear shut the black tank drain valve. You can run some water into the tank through the flushing hose (at the end of this you’re going to want that 10% of water in the tank so this is a bit easier than putting it all in through the toilet).
8. Now you can dump any other grey water tanks you have, if you need to. This flushes out your drain hose to the site’s septic attachment and keeps it clean and cuts down on smell.
9. Fill a bucket with hot water, add the appropriate amount of your GEO solution to it, then dump it in through the toilet. Remember to have your 10% estimate of total water in there.

Other points to consider

So back to the grey water tanks (shower, bathroom sinks, kitchen sink). The drain valves for these should remain closed until dump time just like the black tank, as described in the Procedure, but with some possible exceptions. Those grey water tanks still have small particles going into them, so you still want to have some water in them at all times so the solids don’t dry out. The exceptions would be for example if you have a washing machine connected you can and maybe should open the gate valve in the dumping plumbing while the washing machine is pumping its water out. Another could be that say for example you have several people taking showers one after another you can and maybe should keep that drain valve open until the last person finishes. I do recommend that you periodically add some of the GEO solution to those drains however since you have soapy water already going down there it’s not that big of an issue. It’s mostly just to kill bacteria and keep things smelling okay.

If you bought your rig used, there’s no way to know how the previous owner(s) handled cleaning tanks. I would assume the worst and go through a rigorous cleaning procedure wherein I would first fill the black tank completely then add RID-X, let that sit for a few days, drain it, then refill it and use the Green Goblin product, let that sit overnight at least, drain it, then go through the flushing procedure above and then fill the tank to 2/3, add some GEO formula then take your rig for at least a half hour ride, dump it and see what comes out. If you get a lot of stuff out, I would repeat this again. Nothing would spoil your joy in getting a new-to-you-rig than taking it out for a camping trip only to have your black tank back up! I would also include your grey tanks in this as well, but they probably don’t need as much repeated processing.

What to do if your RV holding tank gets clogged

Despite all this…. So maybe you had company and they used too much paper and not enough water and suddenly when you flush you see that water is rising up into the pipe to the toilet. Or when you are using this flushing procedure and you see that dumping a bucket of water into the toilet, the water doesn’t go all the way down into the tank (and you know the tank isn’t full). So now you have a clog and what do you do? Those tank additives that were supposed to keep this from happening in the first place probably won’t work, no matter how much of it you use.
Here’s what I recommend. First, stop using the toilet. Should be obvious but let everyone know. It might drain slowly so you might risk urine in there, but absolutely no more solids until you have the situation fixed. Here are two products to try, and how to use them:

Green Gobbler and RID-X liquid.
I wouldn’t use products that say they do a great job on grease and hair and don’t mention anything about paper. Both Green Gobbler and RID-X mention paper. RID-X is a product made specifically for septic systems and while you don’t have a septic system, the sludge you might be dealing with is similar. Use one product at a time, dump the entire contents into your plumbing down the toilet. Let it sit for hours, overnight is good. After that, you look into the plumbing pipe beneath the toilet flush flap and if water isn’t standing in there you’ve got a start on continuing it. At that point, do a dump of the black tank and flush using the external flushing kit. See what comes out. If you used the Green Gobbler and some green comes out you know at least some liquid is making it past the blockage. Close the flush valve outside, dump some water into the toilet plumbing and see if it rises indicating some blockage is still there. If the water rises again, continue with another treatment. You can alternate the two different products, there might be differences in how they work and break down things so you get the best of both worlds. Once you get to the point that you bucket of water goes into the toilet plumbing into the tank without backing up, you’ve got the situation handled, except that you need to be really careful now for a while with flushing solids down the toilet, especially paper. If you have hot water available, use that in your final addition to the tank, along with your GEO solution, just like in a normal dump-and-flush procedure.

Other Tips and Tricks
Ice cubes in the toilet plumbing, especially if you have elbows to the blank tank. This might not actually do anything but it doesn’t hurt. You’ll find this idea if you search online. The thought here is that the edges of the cubes bouncing around as you drive can help knock stuff off the pipes and tank. The ice melts pretty quickly and there’s no guarantee it will actually get enough sloshing around to do anything, but it doesn’t hurt anything. Just remember that don’t put so much ice in there that it keeps the toilet’s flush gate (the flap that moves aside when you flush) from closing. It needs to remain closed so gasses and smell don’t come back up from the tank. If you have ice left over that you don’t need, this is a good way to get rid of it. It might do some good and you need that 2/3 of the tank filled for driving if you have a dump at your destination.

Splash a little bit of your GEO solution along with your toilet bowl along with the solids to help it make an easier, slipperier trip down into your tank. Especially if there is a lot of paper.
Instructing visitors who are not familiar with an RV toilet might be somewhat embarrassing to discuss depending on how well you know these people, but at least tell them to use a lot of water…tell them to estimate using the same amount as a toilet flush at home. Along with that, empty and flush your tanks before company arrives so that there won’t be any worries things fill up when the company is there. Check your gauges after they leave….

I’ve mentioned the KleenTank company in this article. I have no affiliation with them but in reading information on their website, I came to believe in their version GEO formula and use it all the time. They have a tank flushing operation that is advertised to get your tanks and sensors factory-like-new clean, and at some point I intend on getting to one of their locations and have this process done—especially if they are able to photograph before and after images!

As always, we love feedback. Let us know your thoughts and how you get best results when flushing your RV tanks.
See more about full-time RVing at www.newliferv.us.

SEE ALSO: “DON’T LEAVE YOUR RV BLACK TANK VALVE OPEN”