Getting water from the process gun, but no media?

If when blasting you notice that it is taking a long time to process or is not processing at all even though water is coming out of the process gun you may have a blockage in your agitation. Our machines work when there is a good mixture of the slurry to water. This is achieved by splitting the flow between the process gun and the agitation nozzle.

Note: the popular misconception is that the agitation hose and nozzle is a media pick-up. 

If you have confirmed:

  • you have the correct concentration of media to water (25 – 30%)
  • your water level is high enough in the machine then check the following…


  • (MARS) Drain the machine and remove flange at rear of machine (f)
  • Remove and clear the cylindrical mesh filter  of any debris that may be blocking it and reassemble.
  • Comet and Mercury have a fixed filter in the sump that needs to be free of obstructions (see pic below).

If issues persist then remove the agitation hose (d) See diagram at the top of the page) from the flow-splitter (b) and run the pump. If water is free-flowing out of the adaptor (a) then shut down and drain the machine and inspect the following…

agitation hose

Agitation hose (d)

  • Check the hose for blockages
  • Feel the hose for any soft spots
  • Check for internal delamination of the hose that may cause blockages

(do not use compressed air to check for blockages as it is an unreliable test)

agitation nozzle

Agitation nozzle (e)

  • Check that it is not blocked with material
  • Check that the urethane is still properly bonded to the body.

Adaptors (a)

  • After removing the hose check that adaptors are clear and that the urethane is bonded firmly to the metal.
  • Delamination of the urethane may cause it to block under pressure.
  • Check the process gun is not blocked
  • Check the nozzle is not worn
  • Remove the back of the gun from the front and check that the air-jet inside is not worn.
mkXI process gun

Replace parts as necessary, reassemble, charge the machine with media and test.

Comet and Mercury

These machines run on the same principles as the larger units but there are some subtle differences when diagnosing a blockage

  1. The filter is fixed and is a perforated aluminium  grid located part way down in the sump. Make sure the filter is cleared of any debris that may cause blockages.
  2. The agitation hose has a restrictor located at the midpoint of that hose as shown
  3. Smaller machines do not have an anti-cavitation feature so unlike the larger machines, if there is a blockage then it is unlikely that you will get water OR media coming out the process gun.
  4. Smaller units may need more assistance to pick up fine media that has packed down over time. This can be achieved by opening the water-fill valve at the back temporarily to stir up the media as the machine is operated. Remember to turn the fill valve off once everything is free flowing or you will cause excess media and water consumption.