Clarke JETSTAR 1800 Operating & Maintenance Instructions page 10

As soon as you pull the trigger again, water at pressure will be ejected.
This process will continue for as long as the machine is switched ON.
WARNING!
Ensure the operator is aware that
when the trigger is pulled, water at
high pressure can cause the lance
to kick fiercely - it should therefore
be held firmly. In addition, care must
be taken to ensure that the nozzle
is NOT aimed at an area where the
water jet will cause damage, i.e.
away from people, animals,
windows - greenhouses etc., and
be aware that splash back could
also cause damage if the jet is
trained on a nearby wall etc.
To turn the machine OFF, press the OFF button (see Fig. 5), THEN........
ALWAYS press the trigger, to ensure there is no pressure in the hose.
Get into the habit of pressing the trigger again BEFORE disconnecting
the hose from the machine.
A high pressure pencil jet or fan spray
may be selected by twisting the nozzle
as shown in Fig.7.
NEVER attempt to run the
machine with the water
supply disconnected, or
turned off
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Fig.7