My service and support techs have noticed quite a few users of the Wagner Control Spray Sprayer, which is the predominant sprayer used for applying pretreatment, are not properly maintaining their sprayers. Now, as much as I would love all of you to buy our SpeedTreater Automatic Pretreater, I do realize that most will continue to use the Wagner sprayer to hand spray. I recommend that once a week you empty out the pretreatment you have in the gun. Fill the container with hot water and spray the gun for about 3 minutes. This helps flush out the entire spray mechanism to keep it running well. Then just empty the water out and refill back with pretreatment.
The one item users tend to ignore are the filters in the back of the sprayer power unit. Over time they do get dirty. If the air flow into the sprayer gets impeded the gun will not spray properly. The filters are inexpensive and very easy to change out. Just unscrew the two screws in the back, take off the cover, and the filters are right there (picture attached below).
Proper pretreating is vital to white ink printing well. Keeping your sprayer in top form will help in applying the correct lay down.
That is why I suggest a weekly maintenance flush with hot water. If it has sat too long it may not be cleanable. The Wagner, being an under $100 gun, uses a large amount of plastic parts in the spray nozzle mechanism. As you probably know by now, the white pretreatment is a relatively sticky solution. If stays clogged too long the plastic parts will probably glue together and be difficult, if not impossible to get clean.
If it has reached that point, rather then replacing the entire sprayer you could just purchase a new front end (picture attached). Just unsnap the power unit from the old front end, snap in the new one, and the gun should operate like new. I've seen the front ends sold at Loew's and Home Depot for about $39. We carry them also.
Maintaining Your Wagner Sprayer 
