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The Johnson TA3P-10 Macerator Pump was originally designed for lavatory waste. I assume the benefit to the grey water tank is that any food particles from the sink, or any hair etc from the shower, get macerated and do not block the pump. 

The pump pulls grey water directly from the grey water tank, through the pump and out of the grey water hose.


Tank Not Emptying

  • Pump Failure
  • Pump not priming
  • Macerator Blocked
  • Clogged Exit
  • Grey Tank Empty
  • Camper at an angle that prevents remaining grey water from emptying


Pump Failure

No noise at all from the pump could indicate a pump failure. Check the break for the pump on the camper breaker panel. Use a multimeter to test the power at the pump.

(James Young)


Pump not Priming

I’ve had difficulty getting the macerator pump to prime (pump whirring correctly, but not picking up water) and apparently, others have as well. Solved this problem by putting suction on the pump outlet with a simple transfer pump and switching macerater pump on.

(Joseph Braun)


Macerator Blocked

If the pump ‘whirs’ but is not pumping out the water then the macerator may be clogged / stuck. Sometimes this emits a squealing noise.

If that happens, switch off the pump, use a small electrical screwdriver to remove the top cap of the Grey Macerator Tank. This exposes a metal block with a slot for a flat head screwdriver, I assume this is the auger.

Using a flathead screwdriver rotate that metal head to turn the shaft and free the blockage. You can turn clockwise or anti clockwise BUT whatever way you choose finish by turning it a turn anticlockwise. I believe this sets it up in some way but not sure how.

It was easy enough, worked first time when I switched it back on. Instructions are in the XP manual, thankfully Claire thought of looking there.

(James Young)



Camper Angle

Earlier models have a pump hose attached to the side of the tank. This causes a mixture of air and water when the grey water levels gets too low. Or, worse still, just air of the camper is angled away from the hose. In this instance, placing some blocks under the wheel diagonally opposite where the sump hose is attached will ‘push’ all the water up to that end and allow the pump to empty cleanly.

Later models have the hose inserted in the top of the tank, almost touching the bottom of the tank. This helps reduce the water / air mixture. This fix has been done on some early campers, look for tips elsewhere in this post.

(James Young)



Keep Grey Tank Clear of Debris

Keeping the grey tank clean and clear of larger debris will be beneficial to the grey tank macerator pump. Some use a washing up bowl in the sink, throwing the water away outside the camper. This reduces food particles and such from getting into the sump tank and then the grey tank; meaning obvious benefits to both.

(James Young)

Grey Tank Cleaning

Running a grey tank cleaner through the system will help reduce grey water ‘smells’ especially in hot weather. Regular cleaning helps, regular emptying helps too.

(James Young)

Stay ECO to dump anywhere

Using environmentally friendly soaps, detergent etc and not adding anything toxic to the grey tank means that you can dump it anywhere, within reason. It is worth noting that even ‘environmentally friendly’ soaps like Meyers or Dr Bronners can be bad for lakes, streams, rivers etc. So, if you do ‘wild dump’ do so away from a water source.

(James Young)

Hose Nozzle

Our fresh water drain hose and our grey water pump hose finished with a ball valve only. This meant the water sprayed out of the end, rather than coming out in a nice stream.  A bit messy with the grey and the fresh water was awkward to get into small holes, like adding some to the toilet for example. We added a connecting screw thread, usually used for connecting two threaded plumbing items. It makes a nozzle and therefore a nice steady stream of water.

Another option is to add a hose connector to the end. You get a steady stream, plus an option to add an additional hose should you need to. 

water hose nozzle

(James Young + Gerhard Faessler)