2.Active vocabulary:

3.Answer the questions:

1. When do we install a septic tank? 2. How does a septic tank work? 3. How long does it take daily waste water to pass through the tank? 4. What is the function of a grease trap? 5. What does the location of a septic tank depend on?

Text 8 (1400)

1.Read and translate the text: Discharging the effluent

Effluent is discharged into soil soakaways such as seepage pits or subsoil irrigation systems.

The efficiency of the disposal of the effluent depends on the ability of the soil to absorb it. Before you decide where to build a septic tank, you should carry out a percolation test as follows:

1. Dig six holes that are about 600 to 900 mm deep in the area where the effluent will dis­charge.

2. Fill the holes with water.

3. Twenty four hours later reduce the water level to 150 mm.

4. Insert a measuring stick in each hole and calcu­late how long it takes for the water to fall 25 mm.

Using this method you can refer to Table 7 to determine the absorption capacity.

Table 7 Absorption capacity

Time taken for water level to fall 25 mm (in minutes)	Absorption area per person (m2)
2 or less	4
3	5
4	6
5':	6.5
10	8
15	9
30	13
60	17
More than 60 minutes	Not suitable for effluent disposal

Seepage pits. Seepage pits are most successful on steeply slop­ing sites or very small plots. When the effluent enters the pit, it gradually seeps into the surrounding soil. The pits consist of one or more holes dug in the ground and lined with brick or blocks. The spaces between the material should be filled with stones. Put a concrete cover over the pit and add at least 300 mm soil on top.

Subsoil irrigation. A subsoil irrigation system consists of lengths of drains connected to the septic tank. About 5 metres of drainpipe is needed for each person using the tank. You can connect more than one drain run to the system.

You construct a subsoil irrigation system by digging a trench 450 x 450 mm that has a slight fall. Then lay a 150 mm layer of ballast in the bottom. Put the drainpipes on the ballast with the joints left open before you cover the pipes with 50 mm of ballast. Fill up the trench with soil to ground level.

2.Active vocabulary:

3.Answer the questions:

1.Where is effluent discharged? 2. What does a percolation test check? 3. How does a seepage pit work? 4. How is a pit constructed? 5. What does a subsoil irrigation system consist of?

4.Check your understanding

• A system of sloping drains provides drainage under the ground.

• Waste matter and water are carried away from a building by gravity.

• The drains may connect to a public sewer which carries the effluent to the sewage plant for treat­ment.

• A septic tank can take waste water if there is no public sewer.

• Drains must have the correct falls and comply with local building regulations to ensure safe and efficient operations.

• The pipes used for drains can be made from rigid or flexible materials.

• The pipes can have rigid or flexible joints.

• Manholes provide access to drains for inspection and cleaning.

• A septic tank treats sewage on site by using bacteria to break it down.

• Drains must be tested for leaks before being covered over.

Notes

by gravity – самотеком;

comply with local building regulations – соответствовать местным (региональным) строительным нормативам

Text 9 (2800)