Graco X5 Owner's Manual page 27

Always ground a metal pail: connect a
ground wire to the pail. Clamp one end to the
pail and the other end to a true earth ground
such as a water pipe.
3A3208B
To maintain ground continuity when
sprayer is flushed or pressure is relieved:
hold metal part of spray gun firmly to the side
of a grounded metal pail, then trigger the gun.
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Reference
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