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According to the IMC, the pipe should not be less than ¾
inches in diameter and should not be decreased in size from
its connection at the con-
densate pan to the point
where the condensate water
finally clears the pipe.
Drains always should be
installed pitched toward its
discharge point. Manufac-
turers often recommend a
drop of about ¼-inch per
foot; the code allows for
1/8-inch per foot. Good
strapping is important to prevent sags, as sags lead to clogging.
Inspectors need to be careful crawling over these pipes in
attics and in crawl spaces because joints that rarely are pres-
sure-tested before they are put into service have been known
to pull apart. What’s more, when subjected to extreme cold,
some plastic pipes and fittings such as those made of PVC
become brittle and break easily.
Secondary and auxiliary drain SySTemS
Equipment manufacturers emphasize that along with a good
primary drain installation, additional measures should be
taken to prevent an overflow from damaging the building.
The 2006 IMC requires this and gives installers several op-
tions. According to the IMC, a second overflow drainpipe,
connected to a higher fitting on the primary condensate pan,
is one option. When this is done, the code says, “the overflow
drain shall discharge to a conspicuous point of disposal to
alert occupants in the event of a stoppage.” The rationale is
when the primary drain becomes blocked and causes water
to suddenly drip from a normally dry pipe, someone will
notice and call for service.
In my area for attic-installed equipment, we like to discharge
the overflow drain from the soffit above a major window. We
have many attic units. Water dripping in front of the window
alerts someone that the HVAC system needs attention.
Regardless of how this is done in your area, when you find a
secondary drainpipe, try to determine its discharge point and
explain the purpose of the pipe to your client. Also explain
the potential consequence of inaction should water appear
from the pipe.
An auxiliary or emergency drain pan placed under cooling
equipment installed in attics often is used to protect the sur-
roundings and is another method of protection allowed by
the code. The pan can be supplied with its own independent
drain or a water-level detection device that will shut off the
equipment before the pan overflows. As with a secondary
drain, if a drain is installed for the pan, it must discharge in
a location that will alert occupants to a problem. No trap
should be installed on the auxiliary pan drainpipe.
During an inspection, be sure overflow and auxiliary drains
are independent of the primary drain. Installers often will tie
the two drains together at
or even several feet away
from the equipment. Tying
both drains together any-
where along their run ne-
gates much of the value of a
secondary drain
(see photo
below)
.
For years, HVAC techs
have been installing water
level detection devices
known as float switches in the auxiliary drain pan. But more
recently, techs have begun installing float switches that will
shut off the equipment if the primary condensate pan itself
fails to drain. By properly positioning the device in the pri-
mary drain or secondary drain opening, it can react to the
condensate before it overflows the condensate pan. The EZ
Trap Switch can be easily installed in the secondary
drain fitting, in the system’s drain piping or trap. It
also can be wired to not only cut off the cooling equipment
to prevent an overflow, but it can be wired to simultaneously
activate an alarm
(see photo above).
Adding a float switch to a plumbed auxiliary pan provides a
high level of protection, but the 2006 IMC is good with the
switch alone. In some cases, especially during replacement or
upgrade work, installing the actual plumbing to handle the
condensate flow from a secondary drain or auxiliary drain
“Inspectors need to be careful crawling
over these pipes in attics and in crawl
spaces because joints that are rarely
pressure-tested before they are put into
service have been known to pull apart.”
During this
inspection, the
primary and
secondary drains
were discovered
tied together,
negating much of
the value of a
second drain.
Photo TS Hart.
The EZ Trap Switch shown here can
be easily installed in the secondary
drain fitting, in the system’s drain piping
or trap. It also can be wired to not only
cut off the cooling equipment to prevent
an overflow, but it can be wired to
simultaneously activate an alarm.
Photo Gerry Spanger, Airtec Products Corporation &
Marketair Inc.
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