What is a Septic Tank?

If you live out in a rural community odds are that the infrastructure that urban homeowners receive are not available. For this matter rural households typically have their own private sewage system, typically containing a septic tank. Septic tanks are made to be structurally sound and water tight. Many homeowners are unaware of what a septic tank is and the process that happens in their septic tank. Getting a general understanding of a septic tank and its operation can help prevent future problems down the road in your private septic system.

Once you flush the toilet, or turn the facet on where does all that waste water go? In your typical urban household it follows a large complex pathway of pipes where it heads towards a treatment plant to be treated. However, in a rural household it follows the pipes in your house to the septic tank where it reaches the inlet baffle. The inlet baffle drops the waste into the “clear” zone. From there the lighter solids (paper, etc.) would float towards the top to create the “scum” layer. The heavier solids will sink to the bottom of the tank to create the “sludge” layer. In between the scum layer and sludge layer is what is known as the “clear zone”. However this area is not exactly clear as it would contain some suspended solids. Typically the longer the retention time or the further travel distance will result in better separation of the three zones (hence better treatment). Your typical septic tank will vent through your inlet pipe (typically a 4” ABS) and then up and out the vent on the roof of your house. If you notice a smell at your septic tank then usually there is an issue with the grade of the 4” ABS. You could possibly have a water trap or a crushed pipe. If you notice a smell in the house then that is a typical sign of a frozen roof vent. In the situation of a frozen roof vent, pouring hot water down the frozen vent will clear the vent up.

With all the tertiary or advanced treatment systems that are available the septic tank is still doing the majority of the treatment (approximately 90%). This is one reason to have a water tight tank. It is important that septic tanks develop the three zones. It takes some time to develop the scum layer depending on home owner usage (typically between 2 months to a year). If you look down the primary side of your septic tank after 6 months you should see this “scum” layer build up, indicating a healthy tank. On the contrary when there is no apparent “scum” layer that indicates some form of homeowner abuse. This abuse could be over usage of a garburator, heavy detergents, or heavy water usage (no retention time). It has been documented that a septic tank will not start working to is full capacity until 1 ½ to 2 years. This is why it is important to not have your tank pumped out too frequently. Filters are always an essential to have in each septic tank. The fact that the “clear” zone will always have suspended solids is the reason that the 2009 standard of practice stipulates that all pumps be screened before entering its final discharge. There are four typical types of screens and filters.

Effluent filters – these are typically located in the primary side of the septic tank
Basket screens – a submersible pump will sit inside this type of screen
Biotube Pump Vaults/Easy Pack Packages – a turbine style pump sits inside a housing to which filtered water is allowed
Inline filters (Symtech Filters) – this is plumbed into the discharge piping off of a pump.

Gaining a general understanding of your private sewage system can play a major role in preventing problems in your septic system down the road.


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