RV Holding Tanks Are Not Septic Systems

While it is true that septic systems and holding tanks do have some similarities, they have several differences that are certainly worth knowing about. We often see people online claiming that RV holding tanks are not septic systems (true) and therefor do not need to be treated with a treatment (untrue). We will unpack that erroneous belief towards the end of this piece.

RV Holding Tank Features

Let’s run through the features that are specific to an RV, that you wouldn’t find on a septic system.

• Most RVs come equipped with two wastewater holding tanks, one for gray water (collects water from sinks, showers and bathtubs) and one for black water (collects water from toilets only).

• Holding tanks are vented to allow air and gasses to freely move in and out of the tank

• Holding tanks are typically molded with a downward slope which allows the waste and water to flow towards the waste valves.

• Beyond the waste valve, at the end of the discharge line, there is usually a removable cap that can close the discharge pipe to prevent drips and leaks when a hose is not attached.

• Removing the removable cap allows for a sewer discharge hose to be connected to the tabs on the discharge pipe.

• Waste and water flow out of an RV holding tank when the sewer or black tank valves are opened. The waste flows out of the tank through an attached hose, into a sewer port (where it goes into the sewer or septic system) or into an auxiliary tote (where it can be stored for later dumping).

• Sensors for monitoring the level of waste and water are installed on the holding tanks and are connected to a control panel inside the RV.
• RV holding tanks typically range in size from 15 to 100 gallons depending on the size of the RV.
• Maintaining a clog- and odor-free black water holding tank requires the use of a high-quality tank treatment that has the capability of breaking down solid waste and preventing the accumulation of hydrogen sulfide (the gas that makes your tank stink), in addition to following proper procedures for maintaining your holding tanks.

Septic System Features

The Septic Tank

• Septic systems are plumbed from the house or building through an inlet into a septic tank. They typically range in size from 750 to 1,750 gallons for most residential applications.
• All of the wastewater enters the septic tank from the house or building through the same pipe. The wastewater goes through a tee pipe fitting called a baffle, with an open end in the free air at the top and some pipe pointing down to the bottom of the tank.
• The heavy solids settle to the bottom of the tank (sludge layer) and the lighter solids (such as fat and grease, aka the scum layer) float closer to the top of the water in the tank.
• Many septic tanks have an incomplete wall in it with a gap near the middle of the tank, which allows the liquid and floating solids to move between the two areas. On the other side of the incomplete wall is another baffle similar to the baffle at the entrance of the septic tank; this is connected to the outlet pipe.
• At the top of the septic tank are access risers which allow for servicing and cleaning of the tank.

The Septic Field and Beyond

• An outlet pipe runs from the tank to either a distribution box or a pump tank, depending on the style of the dispersal system.
• The dispersal system can be a traditional gravel / stone drain field, a chamber system drain field, a drip distribution system or even a constructed wetland for final disposal.
• Dispersal systems are selected based on several factors including lot size, proximity to bodies of water, soil conditions, depth of ground water tables, and bedrock depth.
• Dispersal systems allow the water that flows out to filter into the soil, which helps to naturally treat the water with microbes.
• Solid waste, from the sludge and scum layers that remains in the septic tank must be pumped out periodically via a pump truck.

Differences between RV Holding Tanks and Septic Systems

• Septic tanks are enormous when compared to an RV holding tank.
• RV holding tanks are quite small and need to be dumped, typically, every three to five days. 
• Septic tanks need to be pumped out only once every three to five years.
• Septic systems typically have a final dispersal system that allows the effluent to be released back into the environment after pretreatment.
• RV holding tanks need to be dumped at an approved dumping station or at a full hookups campground with a sewer port.
• Septic systems can be far more mechanically complex systems that may include a number of electric components depending on the requirements of the system and building.
• RV holding tanks have sensors that show the liquid level in them and indicate when they need to be dumped.
• Septic tank liquid levels need to be checked by removing one of the riser lids and physically checked by either the homeowner or an onsite wastewater professional to indicate when they need to be pumped.

Similarities between RV Holding Tanks and Septic Systems

• Both septic systems and RV holding tanks require treatment products to maintain optimal flow and the prevention of problems.
• Septic system treatments are typically ineffective in RVs and vice versa. (Due to the size of a septic tank versus an RV holding tank.)

• Both septic systems and RV wastewater systems are prone to clogs, backups and odors if you aren’t using a high-quality treatment and adhering to the proper treatment program. 
• Septic systems and RV holding tanks require lots of water to function properly (urine is not water!). 
• Septic systems and RV holding tanks both require a mindful approach as to what goes into them, which is why it recommend that you never allow harsh or caustic chemicals to go down your drains or toilets on either system.
• Both require specific instructions for use when guests use either system as improper use, or overuse, can cause damage.

The Takeaway

We often see people posting online that RV holding tanks are not septic systems, and therefore do not need to be treated with a holding tank treatment. Their arguments is that because a holding tank is not processing the waste, but is simply holding waste for a short period of time before being dumped, that the problems that are associated with septic tanks do not require a treatment.

There are many things wrong with this argument.

1. They are correct, RV holding tanks are not the same as septic systems (we’ve clarified some of the differences above).
2. That doesn’t mean that RV’s don’t have their OWN problems which requires the use of a holding tank treatment to prevent.
3. RV holding tanks are basically big buckets that hold waste for a period of time before being dumped. If they don’t get treated properly, waste will accumulate inside the tank and lead to clogs (we help people with this problem every single day). These problems can easily occur in only a few hours or days! Additionally, as the waste sits inside the tank it can create odors that need to be controlled (we also help people with this problem every single day). Because of these two problems, a holding tank treatment is required to abate these issues.
4. Holding tanks also have sensors to indicate the levels of waste inside the tanks that will become inoperable if they become coated with waste. Holding tank treatments can help prevent this problem as well (a third issues that we help people solve every single day).

   

5. Unfortunately, the majority of RVers don’t understand how their tanks works, nor do they treat their tanks properly, and this leads to a number of costly, and often disgusting, repairs. Tank treatments help prevent these issues. Following The Unique Method will provide RVers with a fool-proof way to treat their tanks to avoid virtually all tank problems.
6. Not all treatments are created equal. The purveyors of the idea that you should not treat your RV holding tanks with a treatment because they are not septic systems have probably been burned by the many bad products that are all-too-popular in the RVing community. There are only a small handful of products that can truly breakdown solid waste (though pretty much all products claim to). There are even a smaller number of products that can eliminate odors at their source (though pretty much all of them claim to). And there is really only one type of treatment that can effectively do both – break down waste AND eliminate odors – bacteria / enzyme treatments. All other types may be able to do one thing (odor control or waste breakdown) but they cannot do both because of the way they work, scientifically. Be sure you don’t fall for marketing hype. Choose a treatment that can actually break down AND eliminate waste, otherwise treatment naysayers are correct – you are wasting your money!

Hopefully this helped clear things up in the great “RV holding tanks are not septic systems” argument! If you have further questions, please reach out in a comment below. We’d be happy to provide any more evidence or clarification if you need it!

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