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Repairs - VacuFlush Bellows Replacement

Last Changed 9/5/2018

Eternabond This is the sign that we had a problem.  Black tank fluid in the wet bay. Eternabondr

Diagnostics showed that the problem was not tank related.  We hooked up the Black tank flush and watched the water flow out the sewer line through the clear adapter with no leakage down the back wall of the wet bay.

When we flushed the toilet, we observed fluid running down the back wall of the wet bay.  So our problem was pump related.

The Bounder has a VacuFlush system. When you flush the toilet, a vacuum on the toilet drain sucks the fluid in the toilet bowl into a reservoir.  The fluid is then sucked from the reservoir through the pump which macerates the materials in the fluid as well as creating the vacuum in the reservoir for the next flush.  The pump, also known as the vacuum generator, pushed the fluid into the Black tank.

When we opened the compartment where the vacuum pump is located above the propane tank, we observed fluid spurting the top of the pump when the toilet was flushed.  Know we knew where the problem was.

First thing is to talk photos to remember how stuff goes.

Eternabond This is the body of the pump disassembled.

This is the top of the pump body.
click on pictures to enlarge

Some notes on the removal of the reservoir and pump from the RV.  Each has four screws that fit into slots on the base. Removing the front two screws and loosening the rear two screws is enough to slide the pump and reservoir out.  There are quick disconnect cables.

Some how mark the position of items as they are removed.  It is very easy to rotate the position of items and be wrong.  How to mark the black plastic parts is a challenge.  Maybe scribe marks?

The pump disconnects from the reservoir by just pulling it out.  It is a friction O-ring fit into the reservoir. The same with the hose from the toilet.

Eternabondr To remove the motor, there are four screws through the square plate the motor is attached to.  You do not need to remove the flathead screws from the plate to the motor.  If you remove the screws, the orientation of the plate to the motor is critical. I figured that out the third time.

Properly positioned, the motor shaft is centered and close to the pump body.

There is a set screw on the cam on the motor shaft.  Mine was too tight to unscrew with an Allen wrench.  I used a pair of water pump pliers to hold the can while I used a wrench on the bolt through the bellows arm.

The water pump pliers also enable the rotation of the cam so all four screw that holds the motor plate can be removed.
click on pictures to enlarge
Eternabondr This is the bellows that sits in the pump body.  The motor strokes the bellows causing the pumping action.

You can see why we had fluid coming out of the pump top.  The bellows was cracked open in one of the creases..

The collar of the bellows has two clamps that push fit around it.  It will be necessary to clean the caked stuff off the collars so that there is a tight fit around the bellow upper lip.

Now the challenge is to force the collars into the top of the pump body and insuring that the arm of the bellows is aligned properly.  The arm need to be inline with the center line of the pump input and output fittings.  If the arm is not properly aligned, the bolt through the bellows arm will not fit into the motor cam.

With the bellows with collars are in the pump body, then the pump top is installed.  There are two seals, one around collar that inserts into the top of the bellows.  The other is a square ring around the pump body.

The pump top can be 180 degrees, the screw holes are symmetrical.  I had that right the second time.

With the top installed, then the motor can be installed.  You have to rotate the motor cam to get all four screws in.  The top stalks of the pump top can appear to be out of alignment, you just need to push the two stalks towards each other to get the last screw in.

With the motor installed, now put the bolt through the bellows arm into the motor cam.  Make sure the face of the arm is parallel to the cam face.

Eternabondr This is the reservoir that the toilet is sucked into and the vacuum pulls the fluid out. Eternabondr
click on pictures to enlarge
VacuFlush Pump This is the hose from the toilet.  It just pushes into the reservoir.
VacuFlush Pump This is hard to see but the lower white hose if from the pump output into a black plastic set of elbows that rise to the top of the Black tank, the flat wall in the background.

The elbows fit into a gasket hole in the top of the Black tank. The challenge is keeping the elbows into the tank and getting the hose onto the pump.
click on pictures to enlarge
VacuFlush Pump Here is everything back together.   

The hardest part was waiting for the parts. Of course a repair like this happens on a long holiday weekend.  Lots of walks to the park bathroom.

Disclaimer: The information in this site is a collection of data we derived from the vendors and from our personal experiences.  This information is meant as a learning guide for you to  make your own decisions  Best practices and code should always be followed.  The recommendations we make are from our personal experiences and we do not receive any compensation for those recommendations.
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