Septic Tank Sanitation

The installation of a septic tank receptable for all sewerage. It brings about the digestion of organic matter and discharges the black water into a French drain to soak away into the ground over time.

The Benefits:

An efficient septic system includes two major components, the tank itself and a French drain. It needs a little maintenance as each component ha a specific function and is designed accordingly.

The septic tank separates solids from liquids and discharges the remaining liquid into the French drain, where it is further treated by natural microbiological process in the soil. It is important that only septic friendly chemicals are used to clean toilets to ensure the biodegradation process functions properly.

For installation, contact a preferred installer in your area. Installers are listed here.

 

Septic Tank Component Structure

For a basic system you will require:

  1. Tank
    • Septic tank – size as required.Standard fittings (fitted inlet and outlet) are included in the price.
  2. Pipes – 110 mm SV pipes Lengths will vary based on installation.
    • From feed from house to first elbow
    • From first elbow to elbow extending out of the tank
  3. Elbows – 110 mm According to pipes
  4. French drain - Size and backfill material will vary depending on installation and preference.
    • Corrugated Iron (size according to hole)
    • Stones/rocks or car tyres

Choose a Tank:

The volume required will depend on how many people will use the facilities on a daily basis:

PersonsTankDimeterHeight
2 – 4 1 250 L 1 550 mm 1 190 mm
2 – 6 1 500 L 1 550 mm 1 280 mm
4 – 6 1 570 L 1 550 mm 1 390 mm
4 – 7 2 000 L 1 550 mm 1 500 mm
4 – 9 2 500 L 1 550 mm 1 710 mm
 

The volume required will depend on how many people will use the facilities on a daily basis:

Note: This is a guideline for a basic installation. Each installation will vary based on the setup and personal preference. It is advised to make use of a professional for an installation this complex

How to Maintain Your Septic Tank

Ensure that only septic friendly chemicals are used to clean all the toilets feeding into the tank as a septic tank is not chemical resistant. Septic friendly chemicals can be identified by viewing the labels on the back of the products. Note: one teaspoon of dishwashing liquid can result in system failure for up to seven days.

Instructions on how to install your Septic Tank

Pre-installation:

Tank Location

The location of a septic tank should be carefully considered and it must be placed on natural soil with a bearing capacity greater than 120 kPa.

Avoid installing the tank

If bearing capacity cannot easily be determined use the provided method of soil classification – which will also assist in determining suitable backfill material.

Soil classification table

Category Bearing capacityVisual appearanceSqueezed in hand & pressure release
Rock Sufficient Rock, Slate, Shale etc.  
Gravel        
Gravel Sufficient • Coarse to very coarse Free-flowing
• Small stones & particles
• Free-flowing
 
Sand Coarse/ Medium sand is Sufficient • Granular appearance (individual grain sizes detectable) • Won’t form a cast when dry & falls apart
  Fine sand is NOT Sufficient • Free-flowing when dry
• Lighter to brownish colours
• Wet cast crumbles when lightly touched
Fine-grained soil        
Silt NOT Sufficient • Very little fine sand
• Cloddy when dry & soft flourlike feel
• Readily pulverizes to powder
• Darker colours (green, blue & black)
• Cast can be handled without breaking
• Readily puddles when wet
Clay • Hard homogenous clay may be Sufficient
• Clay is mostly NOT Sufficient
• Fine textured
• Breaks into very hard lumps when dry
• Difficult to pulverize into soft flourlike powder
• Cohesive when moist & shrinks when drying
• Darker colours (green, blue, black & orange)
Cast can be freely handled without breaking
Highly organic soil NOT Sufficient • High organic content (often decomposed)
• Plant remains/woody structure easily recognised
• Mineral soil finely divided with fibrous remains
• Occur in lowlands, swamps or swales
• Dark or black in colour
 

 

Installation Guide:

1. Excavation process

When excavating be aware of:

  1. a) The surroundings

    Take care not to damage any underground services (telecommunication, electrical cables, water/sewer pipes, gas lines, etc).

  2. b) The Natural Elements

    If ground water is present in excavation hole, continuously pump out the water during the installation process.

LocationDescriptionExcavation depth
Soft in-situ soil Fine sand, silt or clay Min 420mm / max 720mm deeper than the tank’s height
Non-load bearing No ground water will affect the tank Min 120mm / max 720mm deeper than the tank’s height
Load bearing • Ground water will affect the tank
• Traffic will pass over the site
Min 420mm / max 720mm deeper than the tank’s height

Note: Use the table provided to assist with the appropriate excavation depth relative to the setup. Allow between 300 mm to 600 mm on all sides of the tank. Use the table provided to assist with the appropriate excavation depth relative to the setup

2. Prepare the Tank Bed

TypeThicknessProcess
Rocks/rocky soils • Minimum 150mm crusher dust or a coarse sand/gravel mixture
• Bedding to be thicker where hollows or uneven areas are levelled out
• Remove all large/loose rocks and objects that could interfere
Dry installation gravel/coarse sand (no ground water) • 150mm crusher dust or a coarse sand/gravel mixture
• Stabilise bedding layer with 3% cement (1 ½ bags of 50kg cement)
• Spread cement evenly and compact, using mechanical compactor
• Do not wet cement, as the natural moisture form the ground will do this over time
• If the soil is too dry to form a lump when pressed in your hand, add a little water but ensure lump still crumbles when lightly touched
Dry installation soft in-situ soil – fine sand, silt or clay (no ground water) • 2 x layers 150mm crusher dust or a coarse sand/gravel mixture each
• Stabilise bedding layer with 3% cement (1 ½ bags of 50kg cement)
• Spread cement evenly and compact, using mechanical compactor
• Do not wet cement, as the natural moisture form the ground will do this over time
• If the soil is too dry to form a lump when pressed in your hand, add a little water but ensure lump still crumbles when lightly touched
Wet installation (ground water will affect the tank) • Drainage bedding layer of 150mm crushed rock (19mm), use crusher dust or a coarse sand to bind, followed by
• 150mm crusher dust or a coarse sand/gravel mixture
• Stabilise each bedding layer with 3% (1 ½ bags of 50kg cement)
• Spread cement evenly and compact, using mechanical compactor
• Do not wet cement, as the natural moisture form the ground will do this over time
• If the soil is too dry to form a lump when pressed in your hand, add a little water but ensure lump still crumbles when lightly touched

Note: The bedding is the foundation (inside the excavated area) on which the tank will be installed.The type and thickness of bedding will vary, choose the correct process relevant to your setup.

 

 

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