Reduced diameter underground reference electrodes were developed to simplify the installation of permanent underground electrodes in congested locations. They can be installed in a 5 cm (2 inch) diameter bore hole which makes them ideal for retrofit installations beneath paved surfaces. These electrodes are frequently used beneath aboveground storage tanks and between closely spaced underground storage tanks. Since these electrodes weigh about one fifth as much as standard bagged electrodes, they are favored when product shipping costs are an important consideration.
The internal construction and life extension features on reduced diameter reference electrodes are similar to those used for our bagged electrodes with similar design lives. Rather than packaging the entire electrode in a cotton bag filled with bentonite-gypsum backfill, a smaller bag containing this backfill is fitted over the membrane. Since the entire surface of this flexible bag is the earth contact area, this design has lower contact resistance to ground.
Reduced diameter electrodes are easily installed at new construction sites where there is an open excavation or in a small diameter bore hole for retrofitting. After the electrode has been placed in the hole, it is covered with about 5 cm (2 inches) screened local backfill and then saturated with about 8 liters (2 gallons) potable water to activate it. Improved performance can be obtained by adding about 20 percent bentonite to the screened backfill. The potential of the electrode should be checked against a portable electrode of known accuracy before the hole is backfilled.
EDI’s SlimLine™ Reference Electrode (Model US) has a 30 year design life and is considered to be the premium reference electrode for all underground installations in congested areas. We also offer an Extended Life version (Model US50) with a 50 year design life for projects where a longer service life is required. For installation beneath an above ground storage tank, some design engineers prefer using our Dual Element Reference Electrode (Model UD). This model has a 30 year design life Cu/CuSO4 (or Ag/AgCl) element along with an encapsulated zinc element. Reduced diameter reference electrodes can be ordered with an integral rod coupon (Models USI, USI50).