Simply put, the Thermo-Disc is designed to keep the cold air out of your tank and the warm air in. This is accomplished by provding a foam insulation plug with a rubber seal around the circumference. The standard Thermo-Disc includes a thermal resistance of a minimum of R-10 however can be made with greater R values. The flexiable rubber gasket around the circumfence is designed to make an air-tight seal preventing heat from exiting the tank and cold air from dropping into the tank. The rubber seal also provides for a friction tight fit against the interior wall of the riser allowing the disc to be installed as deep as practical into the risers. The Thermo-Disc can be removed and installed in seconds and is made of material that is non-corrosive in a septic tank environment.
The R-10 foam disc is made of rigid, closed cell XPS polystyrene foam that has high moisture resistance quailties. The foam insulation disc is protected on the top and bottom by a High Density Polyethylene contoured pan which also rigidness to the insulation disc.
Many regulatory codes require septic tank manhole covers to be brought to the surface for proper maintenance and inspection. While doing so, the manhole risers, typically made from either concrete or plastic, are added or extended to the grounds surface allowing the manhole cover to be at grade. The poorly insulated riser material allows heat from inside of the tank to escape and allows cold air to drop down into the tank, which then lowers the temperature of the septage in the tank. Also, in areas with a deep frost, the soil often freezes down to the lid of the septic tank or deeper, further causing the septage to lose heat. If the temperature drops to near freezing, the septic effluent will then likely freeze when traveling to the dispersal field or shortly after arrival in the dispersal field.
Insulated manhole covers are often used with such systems, but they only prevent cold surface air from dropping into the tank. They do not effectively keep the cold or frozen ground from drawing heat away from the tank contents through the poorly insulated riser. Alternatively, foam discs have been installed in the risers at a point as far down in the riser that the user can reach. However the foam discs are seldom able to be installed deeper than the frost, thereby defeating their purpose.
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