NARRATOR: Septic tanks are the perfect sewage treatment
solution for houses that aren't connected to a sewage network.
The tank collects and treats domestic wastewater
using a bacterial process to decompose waste.
It filters the dirty water before recycling
it back into the ground.
Septic tanks are usually made of concrete
and have access covers on top.
The waste treatment process takes place
in separate chambers inside the tank.
Steel bars called rebars reinforce the
concrete structure of the tank.
A welder assembles the rods to form a cage,
then he spot welds the rebar with a mid welding torch.
The welded cage will maintain the structural integrity
of the concrete septic tank.
The welder measures the cage's diagonals
to make sure it's straight.
Next, the worker places rebar spacers
to keep the cage centered in the mold and leveled on the floor.
A crane lowers the cage into a custom formwork made
of high strength steel plates.
Workers close the walls around the form
and secure them in place with heavy duty locks.
The crane lowers machined steel cores
to form the interior walls of the tank chambers.
A rigid plastic tube is inserted inside a rubber sleeve
to create a flow hole between chambers.
Using an acetylene torch, a worker
cuts holes in the rebar for access openings.
The mold allows concrete to flow over the rebar
and inbed the access opening covers in the septic tank lid.
Workers pour over 1,300 gallons of wet concrete into the mold.
They use a stick vibrator to eliminate air pockets
and level the walls with the putty knife.
Next, they mix more concrete and pour
it over the top slab rebar.
Concrete blocks are used to keep the plastic covers from
floating in the wet concrete.
While one worker pours the concrete in the mold,
the other consolidates the mixture with a vibrating stick.
Then a worker levels at the top of the slab with the trowel.
Once the concrete tank has cured, workers strip the forms.
They removed the concrete tank using an overhead crane
and a compressed air system, which forces the mold away
from the concrete tank.
The crane takes the strip core away for cleanup.
A worker brushes the top of the walls
and sweeps the floor inside the tank
then he applies a butel rubber tape around the top
of the exterior wall.
This forms a watertight seal between the tank and the lid.
An overhead crane lifts the lid out of the formwork
and brings it to the tank mold.
The crane slowly lowers the lid onto the tank.
Workers keep it align to make sure it seals properly.
Then they label the tank to indicate its capacity.
Next, the mold is opened, revealing
a finished septic tank.
The rubber sleeve molded into the wall
ensures a watertight connection between the pipe carrying waste
from the home and the tank.
This tank is now ready for delivery.
They set the tank in the ground at the client's
home using a radio remote controlled knuckle boom crane.
A septic tank like this will provide
a three bedroom house with a fully
independent sewage system.