The orifice of the cutting head is the smallest diameter of the cutting stream and accelerates the water velocity drastically up to 2200 mph.

When replacing an orifice, the most important part of the procedure is the alignment of the new orifice itself. If it is not properly aligned with the incoming stream of high pressure water, its lifetime will be drastically reduced. If installed improperly, you may ruin an orifice within the first few minutes of usage.

Therefore it is very important to place the orifice in the cutting head correctly and to introduce the orifice to pressure slowly over a period of time starting at zero and "breaking in" the orifice up to maximum cutting pressure.

This last step is one of the most important things to remember when replacing an orifice.

If a new orifice is not "broken in" properly, the jewel will be exposed to maximum pressure too quickly and may actually break, forcing you to replace the orifice yet again.

First make sure that the pump is shutdown and that there is no pressure in the lines. Then isolate the high pressure of the cutting head by turning the hand valve clockwise all the way. This will prevent any high pressure water from reaching the cutting head in the event that someone walks by and turns on the pump. Remove the bottom portion of your cutting head; this could be an abrasive head or a water-only head. This needs to be done with two crescent wrenches. One wrench holds the cutting head in a fixed position while the other one rotates the body itself.

When the cutting head is off, you will see the orifice located in the bottom of the body. Remove the orifice by using a set of needle-nose pliers. If you have an orifice that is shaped like a puck and slides in a tight machined pocket you have to remove the orifice from its body by tapping the body gently on a notebook or something similar that can dampen the shock of the tapping. You should see the orifice slowly begin to slide out.

Once the orifice is out you can clean the body with a product like Simple Green to remove any old residue of Blue Goop. After this we can put the new orifice in the body. Make sure that the jewel faces UP. If you are using a "puck" shaped orifice you have to make sure you do NOT use any Blue Goop on the bottom of the orifice.

Now make sure you clean the threads of the adapter where the cutting head is getting mounted to and re-apply some fresh Blue Goop.

Now screw the body back on to the adapter until it bottoms out. Use two crescent wrenches again to tighten this up. When this is tight we want to open the hand valve again, by turning it counter-clockwise all the way, and then back clockwise a quarter turn.

Follow the steps for breaking in a new orifice.