How to Use a Macerator Pump On Your RV

A long-term free campsite for your RV is great. But what if there aren’t sewer hookups?

Our Situation

We took a work-camping position at a private ranch. Water and electric hookups were available but not a sewer connection.

We came in with empty tanks so had about a week to figure something out.

Pulling the RV out and taking it to a dump station wasn’t feasible - the site was not an easy in and and out situation.

Local honey wagon services estimated costs of $80/week and we weren’t sure they could actually reach us where we were parked.

The ranch owners had two possible spots to access their sewer system. One was about 50’ away and uphill, the other 150’ away but slightly downhill.

We decided to look into a macerator pump.

What’s a Macerator Pump?

If you haven’t heard of these before, think “garbage disposal”. They take the contents of your black tank and grind it up. Once ground up it can be pumped over greater distances through a smaller hose.

Hold onto that garbage disposal idea - we’ll come back around to it.

Some higher-end RVs have macerator pumps installed permanently. Rather than using a the standard RV “stinky slinky” the owners of these rigs play out a normal garden hose to a dumping point. The macerator grinds up the contents so they can flow through the smaller hose.

What We Bought

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Our RV is certainly not high-end so I shopped for and bought this Clean Dump CDTO Twist-On Portable Macerator System from Amazon:


It’s not the cheapest pump out there, but the reviews were better than others. I figured $50 in my pocket wasn’t going to help matters if the pump failed with a half-full black tank.

The Pumping Process

The overall process is pretty straightforward:

  • Attach macerator pump to your RV’s sewer drain point
  • Attach exit hose to the pump
  • Run hose to an open sewer connection or into a toilet, etc
  • Connect the pump to your 12V battery
  • Pull your tank drain valve
  • Turn on the pump
  • Run it until the flow stops
  • Turn the pump off

Here’s a video of an early use of our macerator pump:

Using a macerator pump on our RV

Additional Lessons Learned

I used the macerator pump multiple times a week over a 10 week period.

I learned a few things since making that video.

Get a Clear Elbow

While running the pump you need a way of seeing what’s going on (if you have a weak stomach this entire process might not be for you).

You’ll need one of these clear elbows:

Why?

  • You need to be able to see what’s coming out before it reaches the pump
  • You need to be able to turn the pump off as soon as the flow stops (running the pump “dry” can burn it out)
  • You need to see the results of your backflushing efforts

Backflush Often

What you don’t see in my video (besides the clear elbow) is another hose added to the second water fitting on the pump. This hose lets you blackflush - which is basically shooting clean water back into the drain system.

Why backflush?

When you pull the black tank to drain it the fluids come first. They drain pretty well. Towards the end of the drain more of the solids come out. And they don’t all come out.

Backflushing helps get those remaining solids out.

My black tank macerating process became:

  • Let the pump empty the tank as far as it would
  • Turn the pump off
  • Leave the black tank drain valve open
  • Backflush for 30-45 seconds
  • Turn the pump back on
  • Repeat this process 5-6 times until I could see through the clear elbow that no more solids were coming out

Top-Flush Often

I would also occasionally use our RV’s built-in flushing system. In this case I’d:

  • Turn off the pump
  • Close the black tank valve
  • Ask for help in not getting distracted right now
  • Let the tank fill for a couple minutes
  • Turn off the tank flushing (before the tank overfills, natch)
  • Pull the black tank drain handle
  • Turn on the macerator pump

Pre-Grind As Necessary

I learned to spot the big clumps coming out of the tank. These stress the macerator pump and make it overheat faster. When I saw one I’d:

  • Turn off the pump
  • Turn on the backflushing valve
  • Let the backflush water pressure break up the clump
  • Turn the backflush off
  • Turn the macerator back on

Keep Fuses Handy

I blew a fuse once while dumping and the entire process stopped while I went off on a fuse hunt.

Once I found some I threw another couple in by my battery so if it happened again I’d have them handy.

Gray Tanks = No Problem

Using the macerator pump on the gray tanks was no problem. I could do both kitchen and bathroom tanks at one time without overheating the pump.

Macerator Pump vs. “Stinky Slinky”

By the end of 10 weeks I was so glad to be done with the macerator pump.  I’m glad our RV doesn’t have one permanently installed.

Why?

  • The tanks don’t get as empty without the suction effect you get with the standard slinky hose - even after 5-6 times of backflushing I’d still see solids/clumps coming out.
  • The pump would often overheat, stop working, and needed time to cool down
  • The process took up to 45 minutes for just the black tank
  • The macerator is another “thing” to worry about breaking
  • You still have to handle a “hose which carries the nasties” of some sort - just a thinner one

Other Macerator Options?

Most of the disadvantages of the macerator are due to it being a small-ish 12v pump. What if you don’t need to stay 12v?

Back to the garbage disposal we talked about earlier.

Crafty DIY sorts have figured out how to hack a DIY macerator using a garbage disposal unit.

I expect a 120v-based garbage disposal unit would be both faster and less prone to overheating.

Keeping the Pump?

We’ve been on the road over five years and haven’t needed a macerator before now.

Is it worth keeping?

For now, I am. Having it may open up some opportunities we hadn’t seen before:

  • Longer stays in National Parks where there are only pit toilets
  • Mooch-docking opportunities by friends’ houses
  • Longer boondocking in places where we can’t find a dump station

Are You Macerat’in?

Or are you still using a stinky slinky at the dump station? I can’t recall ever seeing another RVer using a macerator. Have you? Let us know your experiences in the comments below.

Just wash your hands first.

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5 Comments How to Use a Macerator Pump On Your RV

  1. Picture of Rick GarbodenRick Garboden February 21, 2016

    Hi Michael,  We have been using a Sani-Con in our current motorhome. Our previous one had just the standard slinky. Which do I like the best….. hmmm. Well I like both but for different reasons. The Sani-Con takes a while longer to do the job. I used the clear elbow/adapter on both systems and was very thorough on both so even with the slinky I would flush the tanks 3-4 times and now it takes me 6-7 flushes to get it as clean as I want it to be. Probably overkill but thats just me. I don’t want any trouble that would be my fault with the black tank. The Sani-con is certainly cleaner to work with. Just a small little cap on the end of the dump adapter. I will probably have it again on the next coach also just for the ability of being able to pump the waste if I had to and even up hill.  Sorry so long winded.

  2. Picture of TerrenceTerrence April 12, 2016

    Don’t have an RV—- yet—-  but have lived 4 years on a boat.. we used 12v macerator,  at the toilet itself for the flush.  The pump pulls water in and macerates before it ever gets to the holding tank. 
    Makes for less run time and battery pull overall.

    Makes pump out much easier and back flush easy too.  Been wondering how we could continue that in an RV.

    example: http://www.westmarine.com/buy/jabsco—compact-electric-toilets—P003600319

    http://www.westmarine.com/buy/west-marine—macerator-pump—13997911

  3. Picture of Kevin DeanKevin Dean November 02, 2016

    I encountered the black tank flush problem when I ended up staying four months at a campground with spaces left that only had water and electric.  I had four options, break camp and move the RV each time I needed to flush, use my 10 gallon portable tank which required many trips, buy a larger portable which I had no room to store or buy a macerator pump.  I opted for the shurflo macerator. 
    The next problem encountered was the distance.  The closest available dumping location was 300 feet away and up a 7 foot rise about halfway then downhill.  The Shurflo is rated for 50 feet with a 3/4 inch garden hose.  However, while researching the Shurflo pump, I read of several successful attempts to pump 200 or more feet albeit most of those were downhill. 
    So, I made an initial attempt to pump 300 feet.  The Shurflo pump struggled, overheated and the automatic shutdown engaged multiple times until the job was finished. 
    Studying the problem, I thought of a solution.  Harbor Freight sells a 120 volt potable utility pump rated at 1500 GPH for about 70 bucks.  I bought the pump and hooked it up at the end of the first 50 foot run from the Shurflo pump.  I ran a short extension cord reel with an on off switch to my location by the Shurflo.  From there I ran an extension cord to the Harbor Freight pump.  I ran 300 feet of 3/4 inch garden hose from the Harbor Freight pump to my Dump site.  I started the Shurflo and then the switch for the Harbor Freight pump.  Presto!  Easy as pie!  The total 350 feet of garden hose run was no problem for the two pumps working in tandem.  I’m certain I could pump even further!  I emptied the black tank, made several flushes of the black tank and pumped the Grey water tank with no problems every weekend.  Problem solved!

  4. Picture of Carla MillerCarla Miller June 18, 2017

    I have a permanently installed macerator pump on an RV I purchased last year.  I have problems with it not coming on at all. Sometimes it takes a few tries. I wonder if warm weather effects it by heating it up.  IDK. Anyway,  I prefer the stinky slinky.  I don’t know how I would empty the tanks if it decides not to work.  Definitely something else to worry about and not something you don’t want to not have control of.

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