“In the Spring a young man’s fancy lightly turns to thoughts of…” RV Sewage

This post may contain affiliate links.

A couple weeks ago, I was pondering the following question:

Does the decreased flow rate from a maceration-type pump (as opposed to a standard 3 inch hose) cause problems with suspended materials in the black tank “settling”?

Yes.  I actually wondered this.

Upon having a thought like this, most people would chalk it up to that too-big burrito they had at lunch and just let it go.

Not me.  I had to know.  So I came up with an experiment, but the first thing I would need to complete the experiment was a clear black tank.  They don’t make them in clear because, well, ick, nobody really wants a clear black tank.  So I was on my own.

I have absolutely zero experience in plastics fabrication.  Most people would see this as a road block; but I chose to view it as an opportunity to learn new things, make 7 trips to Home Depot, and drive all over town looking for Weld-On #16 acrylic solvent.  (This, according to the internet, is absolutely necessary for such a project).

With my $150 worth of supplies* in hand, my task for this weekend was to build the “Black Tank Simulator”.

*Yeah, I know. But let’s just pretend I didn’t spend $150 on a project so that we can see inside an RV poop tank

Building the Black Tank Simulator

The simulator is just a clear, watertight tank with an open top.  At the bottom, there is a 3” ABS pipe fitting, which leads out about a foot, and terminates into a twist-on 3 inch Valterra blade valve.  With the right tools and the right glue (the internet was right about that Weld-On #16) it actually wasn’t too hard to build.  That solvent was also good for bonding the ABS sewage pipe to the clear acrylic.

But would it hold water?


In spite of my amateur solvent-welding skills, yes!  It holds water.

And will it dump properly?


Yes!  Apparently so.

So we’re calling this effort a success.  Next, I have to develop a standard (and tactful) tank “mixture”, and find a product to test.  I think I’m going to start with “The Sewer Solution”.    So stay tuned for black tank experiments from the Fit RV Labs!

Also on the agenda for this weekend was re-shooting our RV Video Tour.  The sun was out, and the weather mild, so we called for a favor from our friend Kyle, who acted as our camera man for a day.  We got about half done with all the footage, so that’s another video I’ve got coming up.


Hope your first weekend of Spring was as productive as mine!

James is a former rocket scientist, a USA Cycling coach, and lifelong fitness buff. When he's not driving the RV, or modifying the RV (or - that one time - doing both at once), you can find him racing bicycles, or building furniture, or making music. In his spare time, he works for a large IT company.

    10 thoughts on ““In the Spring a young man’s fancy lightly turns to thoughts of…” RV Sewage

    1. Bob Carl

      I am in a somewhat remote area with well water and power. I was considering a macerator pump when I saw your video. My blackwater tank is 30 gal. with a flushing system. I have a 200 gal tank I plan on using to cart the contents of my black water dump and flush to the dumping station about 3 miles away..
      The 200 gal. tank will be sitting on my utility trailer. While the tank is sitting on the utility trailer, the filler opening might be a little higher than the RV black water out valve. Will the Sewer Solution send the contents slightly uphill and is there a minumum water pressure required?

      1. James - Post author

        Yes, it will send the contents up hill.
        I don’t know what the minimum required pressure is, but I doubt the setup you describe meets it.
        Bottom line: I wouldn’t use the Sewer Solution without a pressurized water supply.

    2. Larry Carr

      I just recently saw the series of tests for flushing the black water tank that you posted on YouTube. I’ve been a Flush King user for several years and have a technique that seems to increase the efficiency of that tool quite a bit.
      After the initial tank dump, I use the Flush King to backfill the tank for several minutes. I then shut off the water feed and proceed to “rock” my 5th wheel trailer side to side by pushing against the back corner. I can get a pretty decent rocking motion going with this method. After about a minute of rocking, I drain the tank again. The second drain shows quite a bit of additional debris exiting the tank through the clear discharge tube. After the second dump, I again close the Flush King valve and open the fresh water feed. I repeat the above procedure and then drain the black tank again. Usually this drain cycle shows very little debris exiting through the clear tube. I realize that the tank is probably not spotless inside but this procedure seems to cause enough agitation to help considerably. My 5th wheel Jayco Eagle 31.5 BHDS is 9 years old and I am just now starting to have issues with the sensors giving inaccurate reading. This season I will try some Tank Techs RX to see if I can cure that issue.


      1. James - Post author

        I always switch to externally mounted sonar sensors. That eliminates the tank probe sensor issues completely.

        1. Larry Carr

          The external sensor idea would be great if I was able to access my tanks. Unfortunately, the bottom of my RV is fully covered. I am hesitant to attempt removing it for fear of being unable to get it back on.

    3. Mom

      What would the effect be if we had a way to agitate the tank before emptying? Say something we could drop into the tank that would agitate while driving?

      1. James - Post author

        I’m not aware of any such product, but it’s not a bad idea. It would have to be some kind of two part impeller, coupled by a magnet, with the motor outside and the blades inside. Something like that would most likely need to be included by the manufacturers. But it’s not all that bad of an idea for a product – if it works, which I don’t know.

    4. Tom Boles

      Hi James,

      I look forward to your test. I have used the Sewer Solution exclusively for the past 14 years on 4 different trailers all over the US. I think it’s an awesome device that has ALWAYS worked well. When my kids were little, we used to call dumping the tanks “Watching poop TV” because of the clear plastic window in the end of the Sewer Solution. The fact that you can use common 1″ PVC pipe and couplers to extend the output up to 60′ feet means you have ultimate flexability in when and where to dump. Try that with a stinky slinky.
      One thing to consider is that many black tanks have either a slight slope to their bottoms, a molded-in channel or some other feature to guide the good stuff to the outlet.
      Have fun and try not to get any on ya.


      1. James - Post author

        Hi Tom –

        Like you, a lot of folks swear by the Sewer Solution; that’s why I’m eager to test it! I agree that it gives you flexibility that you won’t have with a 3″ dump hose, and I’ll mention that in the video I make. But the standard RV advice is to not dump until the tanks are mostly full so that you get the “rush” out of the tank – and that’s what I’m really trying to test. If the “rush” is as important as people say, then things which slow the flow run counter to that advice. But perhaps I can test the “pumping uphill” in some way. I’ll have to think on that.

        And you’re absolutely right about the tanks sloping toward the outlet. I considered trying to build the tank that way. But that would have required bevel cuts on the plastic, and angles in the tank. Since it was my first attempt making a tank, I decided against that. When I run the tests, I’ll put a 2×4 under the far end of the tank to slope it. As long as I run all the tests with the 2×4, it should level the playing field.

        If you have any other suggestions to improve the experiment, let me know!


    Leave a Reply

    Your email address will not be published. Required fields are marked *

    Comment moderation is in use. Please do not submit your comment twice -- it will appear once we have had the chance to review it.