Friday, December 13, 2013

Replacing the Macerator Impeller

Before starting, make sure that the house battery is off or disconnected. Clean and empty both holding tanks. Some waste fluid is expected to drip when you start disconnecting the macerator inlet and outlet ports, so be prepared. I used a small bucket to catch all the remaining waste fluids in the line.

1. Raise the passenger wheels on ramps for easy access to underside of the RV. I made wooden ramps for these purpose. For safety, chock the driver side wheels to prevent the RV from rolling off the ramps. 

2. Loosen the 4 bolts/nuts holding the macerator intake port to the drain pipe, be ready for any liquids. Let the liquid drains into the bucket or container of choice, and then stuff some paper towels/rugs to the pump and drain pipe opening. Loosening and removing the 2 upper bolts/nuts is not easy, as space is really tight to maneuver a tool in that area.

3. Now unscrew the discharge hose holding clamps (x2) from the macerator shield. Using a utility knife cut the hose a quarter inch past the pump discharge outlet port. Roadtrek used some kind of sealant around the pump discharge port making the hose impossible to remove.
4. Unscrew the small white plastic clamp that holds the gray waste gate valve cable.

5. Unscrew the metal strap that supports the waste gate valve into the pump shield.

6. Disconnect the impeller extension turning rod. Just unscrew it from the rear end of the macerator pump by undoing 2 set screws.

7. Trace the positive power wire from the pump unveiling it from the plastic split wire loom, then cut the wire just next to the butt connector. The negative ground wire is connected to the pump shield and no need to remove it as the pump and shield needs to be removed in one piece.

8. Unscrew 2 small self-tapping screws that hold the pump shield front side (facing the passenger side) to the exhaust heat shield (not pictured).

9. Unscrew (x3) the pump shield support rear side (facing driver side) from the frame, the shield with the pump inside should now be easily pulled out.

10. To get to the pump, you need to disassemble the pump surround shield first. Remove the 6 rivets (3 on each side) that hold the shield top cover. Then undo the 4 bolts/nuts that hold the pump to the bottom of the shield.

RT has welded a square plastic piece to the pump intake port; this connects with 4 bolts/nuts to the holding tank drain.

11. Undo 3 bolts that hold the plastic intake port. Removing the bolts is somewhat tricky as the bolts are blocked by the square plastic piece of the intake port. I used a #2 Philips head bit and a ratcheting wrench to inch the bolts out.

12. Remove the steel cutting blade nut. There is a slot in rear end of the motor for a flathead screwdriver to manually hold the shaft while loosening the nut the secures the steel cutting blade.

After removing the steel cutting blades (remember the blade orientations), the impeller housing should easily slide out the motor shaft. The impeller "paddles" are almost gone, and now feels spongy compared to the rubbery new set. I'm not sure if using tank chemicals has played a role to the degradation of the impeller. The old impeller is green while the new impeller is blue, maybe it is made of different material so it has different feel to it.

13. All you have to do now is to reverse the process to reinstall the pump.
Shurflo Macerator parts diagram

Additional notes/tips:

Use watertight butt connector when reconnecting the pump positive wire.

A regular screw hose clamp can be used to secure the discharge hose to the pump outlet port. RT used an ear hose clamp of some sort and I did not have the right tool to remove it, a wire cutter did the trick.

Applying a small amount of silicone sealant around the pump outlet port before connecting the hose is a good idea to provide a watertight fit.

Immerse the discharge hose end in hot water (nearly boiling), after few minutes the hose should be sufficiently soft to easily thread it to the pump outlet port.

Good luck.


  1. Thanks for the great macerator repair blog. Just pulled mine. Mushy green inside. Do you remember where you bought the impeller repair kit? I see there are a few companies out there, but thought I'd ask. Thanks in advance, Doug (Ho-hum on Sprinter Source)

    1. Hi Doug, first I apologize for the really late reply. I was out on a roadtrip for weeks, no internet connection were we stayed. Anyways, I got the impeller kit on Ebay, it is part number 94-571-00 by Shurflo. Hope that helps.

    2. Thanks. Roadtrips with no internet are the best. True vacation. Got the part at a local marine supply. Thanks again for the great write-up. Your remote macerator mod is of great interest. Next project.

  2. You are post a very nice blog. I got my information through your blog. please keep it up.I like it. Water Discharge Hose


Unfortunately due to high levels of spam, all comments are now moderated before they are posted. Thank you.