Insulating a septic system or a domestic wastewater treatment plant for winter in cold climates

Posted on 04 Dec 2019 by Fabian Belin

Insulating a septic system or a domestic wastewater treatment plant may be useful in cold climates in order to maintain sufficient temperatures in the tank while preventing freezing of all effluents. Keeping heat within the septic system will ensure efficient active digestion and efficient wastewater treatment process.

Indeed, the bacterial activity in charge of the wastewater treatment process will drop in the septic system as outside temperatures go down: The bacteria will become dormant when temperature goes below 4°C inside the septic system.

To avoid this, external walls of the tanks, lids and eventually risers may all be insulated using appropriate building material. Various possibilities exist: First of all, an insulation board may be placed on top of the septic system as well as along sides of the septic tank prior to start backfilling. At the same time and to ensure proper insulation of risers, a flexible insulation material may be wrapped around extensions if any.

A specific attention needs to be brought to the most sensitive and exposed parts of the septic system which are the lids. Wastewater Treatment Plants manufacturers might offer septic systems already equipped with pre-insulated lids. Alternatively, insulation can be added on site by the contractor in charge of installation of the tanks.

Deepness of installation of the septic system in the ground is also key. The tanks should ideally be buried at a minimum depth of 500 mm below ground level, outside of freezing zone and frost line, to ensure efficient operation of the wastewater treatment system in cold climates. In case the septic system is buried at a more shallow depth, then additional insulation may be required.

The use of spray-on insulation may be used to ensure additional insolation at seal points. This extra care in cold climate will ensure that cold air is not drowned into the septic system, which might lead to freezing of water distribution pipes and eventually liquids in the septic tank.

Finally, a few recommendations about the material used: The insulation material used should be suitable to be buried to the ground, and should be resistant to water absorption. A higher R-value of the selected insulation material will allow better thermal performance of the insulated septic system.


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