Check your macerator pump

I love the Sanicom system on our PC but it has a design that seems to me to be trouble waiting to happen.  Or, maybe, I just was unlucky.  The Thetford pump is supported on our PC by a U bracket below the system access door.  The location of the bracket (which looks like something PC probably makes for their rigs) was just a little off kilter resulting in a not quite right alignment and apparently put a bit of a strain on the connection between pump mounting bracket and the pvc pipe coming from the tanks.  Given a few thousand miles of vibration going down the road, the mounting on the pump (which is a bayonet) failed.  The result was  leakage of fluid at the point where the pump joins the piping.  There is an O ring at this point between the pipe and the pump bayonet.  

The problem is the bayonet.  It has four ears and three of the four on my pump failed.  Failed is a nice word.  Those suckers broke off leaving the pump attached to the  pipe with only one of the four appendages.  

I took the whole shebang apart this beautiful (sunny and 70F) day and took it into my shop, cleaned it, modified it and reinstalled.  I put a good sealant all around the joint and that will obviously have to be scrapped off if I ever replace the pump, which I doubt.  This is our second RV with a macerator and if you take care (particularly to use a hair trap on the drain in the shower and not put really dumb things down the gray drains in the sinks) they give great service in my experience.  

I add all this to the forum to simply caution my fellow PCers to consider visually checking the integrity of the bayonet on their rigs when they do their spring "gettin' ready to go" stuff.  

Researching this on several Class C forums, I find I am not the only one to have had the problem.  The bayonet is simply under structured from a design standpoint.   Competing (non Thetford) pumps used in RVs apparently use a threaded attachment as opposed to the bayonet.  

Paul

Thanks for sharing that Paul.

Our 10 year old PC with macerator pump is supported by Phoenix's original method using generic perforated strapping (pictured below).  The installation never looked impressive so one day I set out to make a clean "U-Strap" just like the ones Phoenix has been using for a number of years since.  It didn't take long for me to leave well enough alone because significant upward stress had that connection you mentioned, leaking.  I did check the 4 bayonets and they were all good, none had cracked.  The generic perforated strapping is flexible, providing just the right amount of support in all directions.  And maybe it provides just the right amount of "Give" on bumpy roads.  It is working so well right now, it's hard to bring myself to mess with it just so it looks better.

With 3 of the 4 bayonets broken on yours, maybe the "U" strap is too tight for bumpy roads.  Consider adding some washers between strap and RV to relieve the upward pressure and add thin foam weather stripping as a cushion between the pump and strap to allow for some limited movement on bumpy roads.  Maybe that will resolve your breakage, and maybe quiet-down the pump too.

Ron, you are right on target with my thoughts.  I did modify the U strap in such a manner as to accomodate a little "give" and essentially dampen vibration.  The best solution would probably be a rubber hose between the bayonet's receiver and the sewage piping, but that would be a really major project.  As I recall, my previous rig (Roadtrek Class B 210) had such a short rubber piece of tubing to connect the pvc sewage pipe to the the macerator, thus absorbing all the vibration/give.   

On my Roadtrek, I had a macerator discharge hose split after a few years use.  It failed, of course, while I was running the pump dumping the tanks.  The split was perfectly aligned..........to soak my right leg at about the knee level.   Montrose, Colorado.  July, 2010.  You remember times and places for "certain memorable events".   

Paul

Doneworking.....there is no doubt the m-pump hangs out there some and I am sure there is some significant movement back to the coupling.  I would find it hard to believe that there would be enough flex/pressure to break all of the ears on the coupling.  My bet is at some point you backed up into a banking and the pump hit and that is what broke the ears; happened to me once in my back yard and I never felt a think.  Week later saw a small puddle under the coupling.  I may be wrong but I am just saying!  Good thing is PC has the new pump coupling and the job is very easy.  Best of luck

ragoodsp, I thought perhaps that had occurred (bumping it on something)  but when I made the repairs I took the pump into my shop, cleaned it and examined it carefully.  There was not a scratch on it.  So, the only conclusion I could make was that the misalignment (which was obvious when I put a straight edge from the pump to the plumbing) over time and rough roads had something to do with it.  When I modified the C clamp discussed above, the pump was resting about a quarter of an inch lower in the clamp to achieve an inline lineup.

In reality, who knows what mischief was at work?   

Paul

We had one of the bayonets crack a few years back. We caught it when it had just a small leak as the parts started to separate. When we took it to an RV repair shop, they called Thetford and the parts and repair were free so I think this is another of those items that the manufacturer knows has issues but they either don't have a better solution or just don't want to deal with a recall. They fix them as they go... and as complaints come in. We hit the same deal with the Onan generator fuel pump, the Atwood Furnace igniter, the lense covers on the motion sensor for our outdoor light and then the Thetford macerator bayonet. They know there is an issue, they just don't recall them.

Another macerator issue for which there is an older thread regards the damage the screw that holds the aft most hose bracket can cause to the hose where the screw protrudes though the compartment wall.
It's a self tapping screw that protrudes  3/16th of an inch or so and can puncture the hose.
I remember reading the original post but forgot about it until a week or so ago while pumping I suddenly had a significant leak. I believe what happens is when the pump is running the section of hose between the bracket and elbow whips around violently and comes in contact with the tip of the screw.  I think it is worse with the new turbo pump or whatever it's called.
While waiting for a replacement hose and an opportunity to replace the screw I have removed it and first wrapped the holes, at least two with stretch and seal tape then wrapped it with multiple layers of duct tape.  I continued wrapping through the hole in the compartment as it is a very rough cut surface and am concerned that with time could wear into the hose.
So far the repair is holding up.

2Frazzled,  could you please elaborate on the Onan generator fuel pump issue you referenced?  I am aware of water intrusion and circuit board issues with the Atwood furnace.  Was your igniter problem related to these defects?

2Frazzled,  could you please elaborate on the Onan generator fuel pump issue you referenced?  I am aware of water intrusion and circuit board issues with the Atwood furnace.  Was your igniter problem related to these defects?

Re: Atwood Furnace - no, though I suspect some people got stuck paying for new circuit boards when it was the igniter itself. Our igniter was either bad or not placed well. We never clarified, they just replaced the igniter and adjusted things and it's worked ever since. Several folks on this forum have posted that they had pinholes in the ceramic on the igniter which allowed the electricity to arc so they didn't get the spark at the end. Others had igniters that sparked but too far outside the propane gas chamber to ignite. Ours would ignite at warm temps so we suspect the placement was partially our problem.

Re: Onan generator - again, we just took it in and they fixed it. Folks on the forum told us they had read about bad Onan fuel pumps so we used those words when we signed up for service "we think the pump is bad, it isn't running" - this got us a warranty repair instead of a mechanic saying there was varnishing that required a full rebuild. Our genny worked fine once then the next time, nothing. Our wonderful forum told me to go out and stick my head near the generator when we tried to turn her over and listen for the pump to kick on. It never did so we knew that was the problem.