National Oilheat Research Alliance 13
Tanks were manufactured of various gauge
steel over the years. The current UL 80 standard
requires a minimum of 12 gauge steel
thickness (0.1046 inches). Older tanks may
have been fabricated of 14 gauge steel. These
tanks are almost 25% thinner than what is
mandated today.
A UL 80 tank must have a ½" (minimum)
outlet underneath the tank to facilitate water
draw off. When this tapping is used for the fuel
supply connection, it also serves as a bottom
draw off for any water in the tank—provided
the tank is properly pitched.
If the tapping is not used for the fuel supply
to the burner, it should be piped to facilitate
removal of water. Merely making the fitting
liquid tight by the insertion of a plug defeats
the purpose of the design. Typically the tank
top is fabricated with either three or four 2"
fittings to accommodate the fill piping, the vent
alarm and vent piping, the level gauge and the
fuel line(s) when a single pipe configuration
from the bottom draw off is not used.
The typical UL 80 ob-round tank is supported
by 1¼" pipe nipples threaded into the
leg brackets integral to the tank.
UL 80 tanks designed for the mobile home
market and other specialized situations are
available. Some designs presume the tank
may be installed beneath the mobile home.
While this provides the benefit of protecting
the tank from weather conditions, installations
of this nature can impede future inspection and
removal of any accumulated water.
Always check with the tank manufacturer for
a copy of their current tank installation
instructions.
For example, Granby UL-80 Tank
Installation Instructions can be found
at granbyindustries.com/wp-content/
uploads/2017/11/SI0015_Ea-UL-80-
installations-and-maintenance-guidelines.pdf
Externally Coated Steel Tanks
The majority of UL 80 tanks available today
are fabricated with an exterior finish coating
applied to the steel. Manufacturers also offer
tanks with external polyurethane coatings that
better protect the outside of the tank from
rusting and corroding.
Double bottom
tanks
Another improvement
to UL
80 tanks is the
“double bottom”
tank with interstial
space leak
detection monitoring.
These tanks
have a second
bottom to contain
a leak should
internal corrosion
create a breach of the primary tank steel. A sensor
installed in the interstitial space triggers an
alarm and notifies that the inner tank has been
Externally coated steel tank compromised.
Double bottom tank