We get asked about macerators all the time. Why do we need to clean tanks on RVs that have them? Do they work better than the traditional way of draining your holding tanks? What’s our “professional” opinion of them?

Types RV macerating systems

There are two types of macerators, one that is built inline or as a part of your RV’s toilet (which then empties into the black holding tank) and the other than commonly connects to your holding tank’s 3″ sewer hose fitting. This last type could either be a built-in, integrated component that is a part of your motor coach or it could be an aftermarket model that connects as a separate unit.

Almost all macerators are electric-powered, but some are water-powered. Care must be taken with these types, however, as a proper backflow assembly must be utilized to guard against back siphonage of sewerage into the potable water system of the RV park. Diseases that sewage can contain could be catastrophic if that was introduced into the potable water supply. Some RV parks do not allow this type of system as they use an excessive amount of water to function.

How does a macerator work?

RV macerators are very similar to the garbage disposal unit you may have in your kitchen at home. They are essentially motorized grinders that turn your black tank solids or, in the case of inline macerators that are a part of your RV’s toilet, anything going into your black holding tank into slurry that is pumped under pressure longer distances through a much smaller sewer hose — even through a common, 1″ garden hose. And because an electric pump does the hard work (instead of gravity, like in the standard 3″ sewer hose almost every RV features as standard), waste can even be moved uphill if needed.

Why would you want a macerator?

It’s true, handling and dumping waste from your RV can be a smelly, messy job, especially when using the standing 3″ sewer hose or “stinky slinky.” A macerator can alleviate some of those concerns. Because of the smaller diameter hose, there is less smell permeating the air around your RV as waste is disposed of. Macerators may also allow you to dump waste where you might not always be able; at home, for instance (if local laws allow).

The pros and cons of macerators

The advantages or “pros” of a macerator are pretty obvious:

  • Can pump waste up any incline (when is that ever an issue, though?) or over a great distance
  • Less potential for mess
  • Can dump just about anywhere (again, referring to being able to reach an in-ground sewage pipe or drain), even into toilets connected to city sewage

The disadvantages — or “cons” — seem to be pretty numerous, however:

  • Often time, it takes longer to dump your tanks than the standard 3″ sewer pipe
  • Needs maintenance on the pump, especially the impellers. Not knowing this or not doing regular maintenance will result in the pump getting slower and slower, making the pump out process ever longer over time.
  • Excessive pressure in the pump can cause the hoses and fittings to blow, resulting in a pressurized mess.
  • A macerator is expensive (in comparison to the standard 3″ sewer hose and fittings) and standard toilet vs. macerator-equipped
  • Generally, requires much more water to process and empty tanks (whether water-driven or electric-powered)
  • Must be monitored when using: Allowing a macerator pump to run dry can damage the pump, blow a fuse, or even void the warranty on the pump

It’s often recommended that when purchasing a macerating system, get one that has the gray tank bypass. The theory is that you can leave the gray tank’s drain open since its contents don’t need macerating and they can drain into the RV site’s waste drain. There’s a couple of problems with this. As we mentioned in another article, it’s not a good idea to let your gray tank drain slowly. Doing so can result in solids dropping out of any liquid, gathering in pipe corners and turns. However, if you are using a clothes washer, you may want to employ the bypass or go back to the 3″ sewer hose so that the gray tank doesn’t get backed up (disposing of all that water through the 1-1/4″ could potentially be trouble).

What can go wrong?

Well, plenty, as it happens.

When an RV has a macerator-equipped toilet, the macerating process is effectively liquifying solid waste. This results in a likelihood that what goes into and stays in the black tank will be even more sticky and potentially cause even more problems (like misreading sensors).

Things can get stuck in the blades (anything that isn’t soft that may go down the toilet or drains). One full-time RVer I spoke to said that he has to rebuild his pumps every two years and keeps a spare one for when his main pump goes out. It’s a good idea to clean out your macerator at least once per year. This allows you to check the condition of the pump and clear the entire system of blockages.

A high-pitched whine means the macerator is running dry, which may indicate a blockage in the pump. A grinding noise, on the other hand, suggests that there is a broken impeller. Remove the tubes and carefully inspect for blockages. Remove any you may find and then try the pump again.

Macerators can cause fuses to blow. It’s an easy fix, but just be aware. You may experience other electrical problems — just use a voltmeter to check electrical connections to ensure no problems with the circuit.

If your system has one, the gray water bypass can get blocked up.

Finally, the flexible rubber impeller blades can wear out over time (when one breaks or becomes ineffective, the pump can take longer and longer to empty, eventually becoming very slow).

How much does a macerator cost?

A good RV macerator pump will cost at least $200 to $300. An entire system (one that is external to your motorhome) is $300 to $400 and can be installed if you are handy. Expect to pay an RV service center a couple of hundred dollars (or more, if it’s an inline system and they have to make accommodations near your toilet) to install a macerating system.

Popular brands and models of macerators

A quick review of most online RV discussion groups, bulletin boards, RV social media sites, and RV club websites will show a few very favored and well-reviewed macerating systems. Among these are:

  • Flojet Corporation, a subsidiary company of Xylem Inc. There are a number of individual pumps and kits available under the FloJet brand. A good starting model to consider is this one.
  • Sani-Con by Thetford. Thetford is a trusted RV parts and products manufacturer. They feature twist-on systems, box-mount, and portable, contained kits.
  • Clean Dump likewise provides twist-on and permanently-installed, inline models. Check out the differences online and make a decision as to which one fits your needs better.

In conclusion

Some RVers say a simpler system is better. More processes, parts, etc. mean more things can break. Most online discussions are split: About half of RVers say they love the macerator systems (ease of use, less messy) while the other half say they are not worth the hassle (things breaking, repairs at inconvenient times or requiring a skill level they don’t have).

If you decide a macerator isn’t for you and you want to stay with the conventional system of a 3″ drain hose that empties using gravity, you should definitely use some sort of backflush process like the Valterra Flush King occasionally to get the black tank completely clean. A macerator doesn’t allow the down pressure of a full tank to happen and clear out everything inside (especially anything sticky).