Is feedthroat leakage causing you problems? The best solution is to plug the exit of the water flow, and install a pressure and a globe valve on the inlet side before the air supply. Fill the housing with water, the put full plant air pressure against the water in the housing.
Close the valve and let it stand over night. Then in the morning check and see if the pressure has dropped off. As long as all of the fittings are tight, there should be no loss in pressure in the testing systems.
Tim Womer is a recognized authority in plastics processing and machinery with a career spanning more than 35 years. He has designed thousands of screws for all types of single-screw plasticating. He now runs his own consulting company, TWWomer & Associates LLC. Contact: (724) 355-3311; email@example.com; twwomer.com