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Copyright © 2005 Watts Radiant, Inc.

Staple Gun Usage Guidelines

LIT#STAPGD0305

Effective: 03/22/2005

USING THE PEX STAPLE GUN

The PEX staple gun is a Senco staple gun, specially 

modified by Watts Radiant both internally and externally for
use with Watts Radiant’s RadiantPEX and WaterPEX. This 
staple gun is fitted with a stainless steel guide plate (Order
Number 81005497) that is bolted to the underside of the
gun. It is designed for both 3/8" and 1/2" PEX. If stapling
3/8" PEX, make sure the smaller 3/8" opening is at the
front of the gun. You should see “3/8" PEX” stamped on the
guide plate at the front of the gun. If stapling 1/2" PEX,
unbolt the guide plate and turn it around so the larger 1/2"
opening is at the front of the staple gun. You should see
“1/2" PEX” stamped on the plate at the front of the gun.

When stapling PEX, position the guide plate over the tub-

ing. Make sure the guide plate, at both front and back, is
placed firmly against the plywood. Before pulling the trigger,
make sure that the tail end of the guide plate is also cen-
tered over the PEX. If the tail of the guide plate is not cen-
tered over the tubing, some of the staples may puncture the
PEX. When the guide plate has completely contacted the ply-
wood and is centered over the PEX tubing, pull the trigger
and fire the staple.

PEX Staple Intervals:

The PEX staple gun should only

be used for thin-slab applications and not “staple-up” or
“sandwich” applications. For thin-slab applications, staples
should be placed every 12" to 15" along the length of the
tubing. Stapling the PEX at wider intervals can result in the
tubing being too close to the sur face of the thin slab. (Watts

Radiant recommends a minimum 3/4" between the top of
the tubing and the sur face of the concrete.)

PEX CAUTIONS:

1.

Examine each circuit after it has been stapled in

place. The PEX staple gun is designed to leave a 1/8" gap
between the top of the tubing and the staple. This is to make
sure that the tubing is not fractured by the impact of the 
staple and to assure that no abrasion is possible between
the staple and the tubing. If the staple is closer than 1/16"
of the tubing, then it should be removed and replaced with a
new staple. Please see the illustration for tolerances. 

2.

As with any floor heating application, do not install

PEX over floors with asphalt paper “slip joint” in the flooring,
as an unpleasant odor may result. Rosin paper (pink colored)
is generally acceptable.

Note:

For best per formance, 3 or 4 drops of pneumatic oil 

(5-weight, non-detergent machine oil) should be installed once daily
into the air inlet of the staple gun. (More oil drops may be used if
the gun sees continuous heavy service, i.e., more than 3–4 hours
at a time.)

USING THE ONIX STAPLE GUN

The Onix staple gun is a Senco

®

staple gun, specially 

modified by Watts Radiant both internally and externally. The
Onix staple gun is fitted with a stainless steel guide plate
(Order Number 81005498) that is bolted to the underside of
the gun. If stapling 3/8" Onix, make sure the smaller 3/8"
opening is at the front of the gun. You should see “3/8"
Onix” stamped on the guide plate at the front of the gun. If
stapling 1/2" Onix, unbolt the guide plate and turn it around
so the larger 1/2" opening is at the front of the staple gun.
You should see “1/2" Onix” stamped on the guide plate at
the front of the gun.

When stapling Onix, position the guide plate over the Onix.

Make sure the guide plate, at both front and back, is placed
firmly against the sur face. Before pulling the trigger, make
sure that the tail end of the guide plate is also centered over
the Onix. If the tail of the guide plate is not centered over the
tubing, some of the staples may puncture the Onix. When the
guide plate has completely contacted the plywood and is cen-
tered over the Onix tubing, pull the trigger and fire the staple. 

Onix Staple Intervals:

You must use one staple every

6" when the Onix is installed under a wood frame floor. This
ensures good thermal contact between the Onix and the
floor, which is essential for the Onix to deliver its specified
heat output. Spacing the staples too far apart can cause as
much as a 20% loss of peak heat output. For initial Onix
placement, or where there is insufficient clearance for the
gun to be used, we suggest the use of Watts Radiant
NailTites to hold the Onix in place. Although not essential, it
can be very helpful for an assistant to hold the Onix in place

while the installer is stapling. This assistant must wear all
appropriate safety equipment. When stapling Onix on top of a
floor, in preparation for installing an elevated thin slab, you
may increase the staple intervals to 12" or 18". Always
maintain the Onix spacing as indicated on the plans or in
associated design information.

ONIX CAUTIONS

1.

Examine each Onix circuit after it has been stapled in

place. If you see that the Onix has been partially compressed
by a staple, you must remove that staple and put in a new
one. The staple can acceptably deform the Onix slightly,
1/16" or less, without causing any difficulties. See the illus-
tration for deformation tolerances when stapling hose.

2.

Do not install Onix under floors containing an asphalt

paper “slip joint” between the subfloor and finish floor, as an
unpleasant smell may result. Rosin paper (pink colored) is
generally acceptable.

Note:

For best per formance, 3 or 4 drops of pneumatic oil 

(5-weight, non-detergent machine oil) should be installed once daily
into the air inlet of the staple gun. (More oil drops may be used if
the gun sees continuous heavy service, i.e., more than 3–4 hours
at a time.)

1/8" gap;
correct
spacing

incorrect
spacing — 
tight

Unacceptable

Acceptable

Acceptable

Deformation

Unacceptable

Deformation

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