How do I clear a blocked holding tank?

How do I sanitize my freshwater tank?

Sanitizing your freshwater tank – even if you rarely use it – is very important. Holding tanks are wet, warm, and exposed to molds, yeasts, bacteria, viruses, and other harmful organisms. Left unsanitized (or used), who knows what will find a home there and cause potential problems. Many respiratory aggravates can be found inside unsanitized freshwater holding tanks, especially.

Sanitizing should be done on a regular schedule:

• Full-timers should perform the process once a quarter or four times a year
• Everyone else should sanitize their freshwater tank at least twice a year (usually after they pull it out of storage and then four to five months later, like mid-summer)

Sanitizing is a relatively easy though time-consuming process. The basic concept is to introduce an antiseptic solution into your tank, circulate it through the RV’s plumbing (so you’re sanitizing that too!), allowing it to sit for a period of time, then flushing it out.

Most RVers use a weak bleach and water solution to do the sanitizing. You can also use a vinegar and water solution, though the concentration is higher.

It’s important NOT to use splashless bleach. That has a lower concentration of sodium hypochlorite, the sanitizing element needed to clean your freshwater tank. You good, old-fashioned bottom-shelf bleach, preferably unscented.

The ratio of bleach to water is important. Use 1/4 cup (2 ounces) for every 15 gallons of freshwater tank capacity. So, for a 60 gallon freshwater tank, you’ll use one cup (8 ounces) of bleach. If you’re using vinegar, double the concentration to 1/2 cup (4 ounces) for every 15 gallons of freshwater tank capacity.

How do you get the bleach into the holding tank without splashing it all over you? The best way we’ve found is to empty your RV’s water supply hose (the sanitary white or, in some cases, blue one), careful pour the appropriate amount of bleach (or vinegar) into the hose, and then attach it to your RV’s water inlet, and fill your freshwater tank. Note that you might have to switch over your supply lever to “tank fill.” Some RV’s have separate freshwater tank inlets for tank fill vs. “city water” (from your RV park’s pressurized supply).

Once the freshwater tank is full (it should start to come out the overflow pipe or outlet), turn off the fill supply. Go inside your RV, turn on your water pump, and open every tap inside (don’t forget the outdoor shower or outside kitchen sink tap, if you have them) until you smell the bleach (or vinegar) scent. You want the bleach-y (or vinegar-y) water solution to be in your RV’s plumbing pipes too!

Next is the waiting game. Common guidelines say to wait four to six hours, but we recommend leaving this solution in your freshwater tank (and RV’s plumbing pipes) overnight. After whatever period of time you decide, the next step is to get the beach (or vinegar) and water solution out of your RV’s freshwater tank and plumbing system.

Use the pump to do this. You can also open your freshwater tank’s low-point drain after the pump has been running a while if you feel the bleach (or vinegar) water will not harm the surface under your RV or run-off won’t be a problem. Be sure to keep your gray water holding tank valve open (so the freshwater tank runoff can exit into the RV park’s waste disposal or handling system).

Next, repeat the whole process (filling the freshwater tank, waiting, and emptying it) with just fresh, clean water. The wait time is the same. You can repeat this process a second time if you wish (we do for our RV, so it’s a three-day process).

What if don’t have all that time? You can double the concentration of bleach- (or vinegar) to-water and just wait two to four hours. Wait time on the tank of just fresh water (the second or even third step) should be as long as you can. With this double-concentration method, you can cut the time down to just one day for a complete sanitization.

What tank additive should I be using?

If it was up to us, we’d prefer that you don’t use any tank additive at all! Why is that? All you really need is water, and plenty of it.

Sufficient water when using your holding tanks – especially the black one – will reduce and even eliminate odors, keep tank sensors working, allow your tanks to drain quickly and efficiently, and let your tanks accept waste to their full capacity.

“But we’ve been told to use some sort of additive!” We know; we get it. As RVers, we were told the same thing and for many years used pods, colorful additives, and just about anything we were given, told about, or bought at an RV store.

But those tank additives – enzymes, biological agenst, and chemicals – all intended to break down what’s in your holding tanks (especially the black one), dissolve your RV’s holding tank’s contents (feces, toilet paper, etc.) – as they claim they will – into a thick, sticky slurry.

That thick mixture is coating the insides of your tanks and fouling up those tank sensors (or the ability of the strip type to get accurate readings). It also causes odors, reduces tank capacity, and slows down what’s coming out (and even prevents the tanks from emptying completely!).

“So we just use water?” Yes, and plenty of it. Here’s some tips:

• When you get to an RV park or resort, add three to five gallons (depending on your total holding tank capacity) to each tank as a sort of “priming of the system.”
• When using the toilet, fill the bowl halfway. Whether it’s #1 or #2, flush the bowl, add another half bowl of fresh water, flush that down, and fill the bowl up halfway (for the next time).
• Empty your tanks when they are 75% to 100% full. A full tank creates a swirling vortex when it is emptied, helping to keep your tanks clean.
• When you’re traveling (and after you’ve emptied your tanks before you leave), add three to five gallons (depending on your total holding tank capacity) to each tank. This helps to lubricate your tank and can loosen any build-up inside.

So the big message here is to use plenty of water and to increase the water-to-waste ratio. The higher the ratio, the better your tanks will work.

But what if you really want to use a tank additive? In this case, we recommend our mixture of Calgon and Pine Sol. The Calgon is a surfactant and breaks the surface tension of the water, making all your tank and pipe surfaces slippery (waste will have a much less chance of building up). The Pine Sol is a great disinfectant and odor-fighter. It’s also a great way to knock down mold in your gray tanks (you add this mixture to both the black and gray tanks).

How do you clean my holding tanks?

Your holding tanks are basically large, plastic boxes that are either cubicle in shape (for most motor coaches) or long, flat, and shallow (most travel trailers and fifth wheels). Some RVs have actually very complicated geometry to them. We’ve seen these in some Winnebagos and Country Coaches, where there are ledges and different heights or nooks within holding tanks. No wonder it’s so hard to get them clean!

So how does Kleen Tank get holding tanks “factory kleen?” We use the cleaning power of concentrated, high-powered water at 1500 PSI (pounds per square inch). How high pressure is that? Well, the pressure of water from your RV park’s (or home’s outside) water spigot is about 50 to 75 PSI. Your RV’s onboard black tank sprayer’s pressure is about 100 to 150 PSI for comparison.

How do we get that high-pressure water into your tank? Simple. We attach a special pipe fitting between your RV’s waste system exit pipe and the articulated sewer hose that removes waste and sends it on to the park’s in-ground disposal or handling system.

Using a special six-chamber, heated commercial water pump, high-pressure water is sent up a tiny flexible hose that ends in a special cleaning head. This head is similar to what a commercial plumber might use to clear a septic line of tree roots, sand, etc., except instead of the head being the size of your fist, it’s about the size of your pinky thumbnail.

The cleaning head has holes drilled into the back of it to create a jet of high-pressure water that no only propels or drives the head through your waste system pipes and into your tanks, but also serves to blast away accumulated build-up within your tanks.

Once we’ve cleaned your tanks out, we use a special reverse-flush water valve that pushes water quickly and forcefully back into your holding tank, filling it up. This is then released quickly, flushing out any residual waste. This process is repeated until the tank is clean and the water coming out is clear.

How do my RV’s tank sensors work?

It’s no wonder your tank sensors are the top frustration of your RVing experience. Almost no RVer’s tank sensors work, almost from the first couple of times you use your RV. We’ll get into why that is later (and what you can do about it!), but for now, let’s talk about how they work.

RV tank sensors come in two main types: probes and electronic strips. Most RVs have the probe type which are small metal nubs protruding into each holding tank (yes, your freshwater tank has them too!). 

Most often, there’s a solitary nub on side of the tank and a stacked array of them on the other side. In this type of sensor, an electronic signal is sent through the solitary nub, which travels through the “liquid” in the tank, and creates an electrical connection with the corresponding nub on the other side of the tank. The higher up the nub in the array is activated, the fuller your holding tank is.

The strip-type sensor uses what might be best described as a type of sonar or electronic pulse which measures the fullness of the holding tank. These types are most common on higher-end motor coaches and can go by the name SeeLevel (though there are other types, including Winnebago’s proprietary system).

Tank sensors fail for many reasons, the most common of which is that “stuff” gets deposited on the nubs and prevents accurate capacity readings. Although far less common for strip-type sensors, thick, sticky build-up in the tanks (especially the black one) can prevent accurate readings as well.

So what causes that build-up in your black (especially) and gray holding tanks? Almost always, it’s the enzyme, biological agent, or chemical tank additive you are adding to those tanks. Those additives are dissolving the tank’s contents (feces, toilet paper, etc.) – as they claim they will – but they dissolve into a thick, sticky slurry. That thick mixture is coating the insides of your tanks and fouling up those tank sensors (or the ability of the strip type to get accurate readings).

The solution? Get your holding tanks professionally cleaned, stop using those harmful tank additives, and start using much more water and, if you want, a tank solution like Kleen Tank’s Calgon-Pine Sol recipe.

In some cases, sensors will fail because of corroded wiring, failed electronics, or just too much hard, mineral build-up on the sensor nubs. A professional cleaning will get them working in 9 out of 10 times, but there’s no guarantee short of complete replacement.

How do I figure out what is draining into each of my holding tanks?

A very good question! While most of the answers might seem pretty intuitive — your toilet drains into your black tank and your shower goes into the gray — there are some interesting counter-intuitive situations that may be present in your particular RV. For instance, a lot of RV’s have sinks in bathrooms draining into a nearby black tank.

There’s an easy process to figure out what is going where:

1. Make sure that you have a clear piece of plastic sewer pipe somewhere between your RV’s sewer waste pipe (where tank waste exits and goes into the flexible sewer hose) and the actual sewer hose. As gross as this sounds, you want to see what is coming out of your tanks (always a good practice to monitor your tank’s health).
2. Empty all of your tanks using the gray/black/gray method. Make sure that they are completely empty.
3. Close all of the tank valve pulls.
4. With either the help of an assistant or by yourself, go inside of your RV and turn on or run water down one sink/shower/toilet/washer drain. Let them run or drain for a few minutes (you want some build-up of water in the tank that the sink/shower/toilet/washer drains into). Turn off the water after a few minutes.
5. Go outside and pull each handle until you find which one is tied to that fixture. Write it down on a note and close the handle when the water is done emptying.
6. Repeat until you’ve run and tested every water fixture.

Why do my holding tank sensors always misread?

That has to be the number one frustration of all RV owners! In fact, we kid in our rally presentations that correctly-reading tank sensors were an option from the factory that few RVers care to include when purchasing their RVs. Hah hah.

Well, there are a couple of simple reasons why your tank sensors stopped working or never read correctly:

Using tank additives. If you use an enzyme, biological, or harsh chemical tank treatment, your tank’s sensors will soon stop working and read inaccurately. Why? That tank treatment is designed to break down or digest whatever is in your tanks. It’s doing just that, but what it creates is a thick, pancake batter-like slurry that sticks to everything (including your sensors!) and is next to impossible to completely get out without a professional tank cleaning. For black tanks it’s worse as what’s in there is pretty bad to begin with, but it can also happen in gray tanks.

Not following best tank care processes. We know that you try to take the best care of your tanks. But we also know that there is a lot of false or misleading information out in the RV community that may be confusing the issue. Here are some points to follow:

• Empty tanks when they’re 75% to 100% full. You want the swirl or vortex to help clean out your tanks.
• Know how to empty your tanks: gray/black/gray
• Don’t equalize the gray(s) back into the black tank
• Turn black tank rinser on while emptying black tank(s)
• If you have one, use the Valterra Flush King Reverse Flush Valve to give ALL tanks a rinse or two
• Use more water, especially in your toilet
• Prime the system after emptying your tanks
• Travel with 3 to 5 gallons of fresh, clean water in each tank
• Get regular professional cleanings

Not using enough water. The water here is key. As RVers, we measure everything in capacities or limits. How much PSI air in our tires? How many pounds can our tow vehicle handle? How much capacity our holding tanks have? Using more water than you think you need is a smart strategy for keeping your holding tanks clean, working properly, and minimizing problems. Use more water.

Do those RV toilet paper shake tests really tell anything?

You’ve doubtless seen those videos. A sheet or two of different types of toilet paper are put into jars of water and shook up. A comparison happens as to which one dissolves more in the water, indicating that one type of TP is the best and should be used religiously in your RV. The problem is, these tests are flawed.

First, you don’t wipe with one or even a few sheets of toilet paper. You have a wad or, at the very least, a length of it folded back and forth into a sort of pad. So any sort of test needs to have the actual amount of toilet paper — in the right configuration (pad vs. wad) to approach accuracy.

Next, you really don’t just flush the toilet paper into a tank full of clean water. There’s other “stuff” down there and things start to mix together and stick to one another. And if you’re using a tank additive that dissolves waste (like enzymes, biological agents, or harsh chemicals), then what you are flushing that TP into is a thick, sticky slurry, not a jar of clean, freshwater.

Also, that section or two of toilet paper you put into the jar of water is a fairly low ratio of TP-to-water when compared to what you are putting in the black tank. With smart and proper water use, your holding tank has a much higher amount of liquid in the tank than your test jar.

Finally, you know all that vigorous shaking you see in the videos? There is absolutely no way you could mimic that amount of agitation in your holding tank unless you drove over a tall cliff or got into such a horrific traffic accident that there’s nothing left of your RV – or you, for that matter!

So what type of toilet paper should you be using in your RV? The answer is…any kind that you want, as long as you are using enough water in your holding tanks and follow proper use guidelines when using the toilet:

• Prime your holding tanks after each empty by adding one to three gallons of freshwater to them
• When using the toilet for #2, start with a half-bowlful of water, do your “business,” flush down, follow with at least another half-bowlful of water, flush that down, then add a final half-bowlful of water to serve as a seal and get you ready for next time
• Never use any tank additive that dissolves what is your holding tanks. The enzymes, biological agents, or harsh chemicals only cause everything to turn into a thick, sticky, pancake batter-like slurry.

What is the grayish chunky stuff coming out of my gray tank?

RVers always think the worst of their holding tanks is the black one. We’re here to tell you that gray tanks can be just as bad – or even worse!

Gray or gray water tanks collect water from drains in the galley or kitchen, the shower (or bathtub, if you’re lucky enough to have one) and, sometimes, the sink(s) in the bathroom(s). What you’ll find in the gray tank is soap, food particles, and parts of “us” including hair, skin, and other bodily waste (other than urine and feces that goes down the toilet, of course). But most gray tanks contain mostly water.

Now, some RVers like to leave their gray tank valves open all the time, most of time until a day or two before they’re ready to dump the black tank, or when they are doing laundry (if they have a clothes washer). In all but the last case (laundry), we don’t recommend that you keep your gray tank valve open.

Why? When a tank valve is open, water, or at least, the more liquid contents of the tank, tends to seep out slowly, leaving solids behind. This tends to be more of an issue in black tanks where the “solids” are larger, but in gray tanks it can be a problem too.

As water or liquid seeps out, any remaining solids (food particles, coagulated soap, hair and skin, etc.) can start to rot and create clumps. Also, because your tank is hot and wet, mold can start growing. That can cause terrible odors and even affect those with sensitive respiratory systems.

What you’ll start to see coming out of your gray tanks are chunks of this decomposing material and growing mold. Unfortunately, both are very sticky and can stay inside of your gray tank, causing problems like odors and even clogs.

Leave those tank release valves – black and gray – closed until you are ready to empty your tanks. Then follow the best practices guide in emptying your tanks to keep them healthy, working properly, and with minimal problems.

How do I find out how large the holding tanks are on my RV?

The quick answer is to consult the specifications section of the brochure for your make and model of RV. You might also check the manufacturer’s website to see if you can download a PDF document of the brochure or other technical documents.

Tank sizes don’t vary too much from year to year in most brands and models of RV’s so if you can’t find the exact year of your model, a year before or after is very likely to have the same size tanks.

A good rule of thumb in figuring tank capacity is that your main black and gray tank, when combined together in gallons of capacity, will just about equal the capacity of your freshwater tank. Of course, for RV’s with more than just one gray or black tank, this general and very approximate rule won’t apply.

RV’s also tend to have larger gray water tanks than black water tanks and as a general rule, tank capacity for different types of RVs is as follows:

Travel trailers: 30-50 gallons freshwater, 25-40 gallons black, 30-50 gallons gray

5th wheels: 80-100 gallons freshwater, 40-60 gallons black, 40-75 gallons gray

Motorcoaches: 80-150 gallons freshwater, 40-75 gallons black, 40-100 gallons gray

Again, these are approximations and your manufacturer’s documentation should be referenced first.