Rural Sewage

Question 1

When do you need a septic tank and what is its purpose?

Answer 1

When there is no city septic system.

Breaks down solids

Question 2

What are the two major components of a septic system?

Answer 2

1. Septic tank

2. Drain field or leach field

Question 3

What are the three layers that make up the effluent in a septic tank?

Answer 3

1. sludge (solids at the bottom)
2. scum (oils and greases float to the top)
3. effluent (clear liquid)

Question 4

Where are the anaerobic bacteria present?

Answer 4

In the septic tank.

Question 5

How long should a septic tank be able to hold sewage for?

Answer 5

24 hours.

Question 6

What five things would you consider when determining the expected daily sewage flow for a septic tank?

Answer 6

1. Number of people
2. Type of occupancy
3. Number of bedrooms
4. If there is a clothes washer
5. If there is a garbage grinder (add 50% to size)

Question 7

What three things would determine the location of a septic tank?

Answer 7

1. Distance from the property line
2. Distance from water sources
3. Distance from buildings

Question 8

What types of things do you take into consideration when sizing a septic field (7)?

Answer 8

1. Number of people
2. Type of occupancy
3. Number of bedrooms
4. If there is a clothes washer
5. If there is a garbage grinder
6. Water table
7. Frost line

Question 9

What would you do if a septic tank is installed but you find that all locations for a septic field end up being either too close to a property line or too close to a water source?

Answer 9

Install a pumpout (holding tank). No disposal field is used in this situation.

Question 10

What is the purpose of a distribution box?

Answer 10

Used to improve distribution to the laterals and prevents oversaturation of one area.

Question 11

What is a distribution (D-box) made from?

Answer 11

Concrete or plastic.

Question 12

What do speed levelers do?

Answer 12

They provide even flow to all outlets of the distribution box.

Question 13

What is the reason for the siphon tank being sized so that it discharges a large amount of effluent at one time?

Answer 13

Ensures that entire disposal field is used.

Question 14

What type of soil would you use as fill for a disposal field? Why?

Answer 14

Porous soil (loam, sandy soil or clay).
In order to allow air to reach the gravel bed.

Question 15

How do you test the suitability of the soil or the proposed disposal field?

Answer 15

Percolation test.

Question 16

Explain how a percolation test is performed?

Answer 16

1. Dig two holes; one at either end of the drain field.
2. Holes must be 12 x 12 inches with a depth of 22-32 inches.
3. Test must be done for 1 hr to see how quickly ground absorbs water in the holes.

Question 17

Rather than using a distribution box to distribute the clear effluent from a septic tank, you may instead install a header. How should the header be graded?

Answer 17

Level with the branches then sloped away from the header at a grade of 2” per foot.

Question 18

What would be required if a private sewage disposal system had the absorption field installed at an elevation above the septic tank?

Answer 18

You would install a pump to pump the effluent up to the field.

Question 19

When performing an inspection of a septic tank, you notice that there is very little scum in the tank. What is the cause (2)?

Answer 19

1. Too much detergent from a clothes washer

2. Broken outlet tee causing the scum to leave the septic tank

Question 20

What is the most efficient and cost effective system to use for a disposal field containing 600 feet of laterals?

Answer 20

Install an effluent tank and a bell siphon to discharge a large amount of effluent at one time.

Question 21

When installing a pipe into a septic tank what must you do?

Answer 21

Cut the pipe with a bevel and apply a lubricant so that the gasket doesn’t rip or tear.

Question 22

What is the grade of pipe from a septic tank to the distribution box?

Answer 22

1/4” per foot.

Question 23

What is the expected grade from the distribution box to the end of the lateral (slope of the trench)?

Answer 23

2” per 100 feet.

Question 24

What is the minimum permissible length of a building drain to a septic tank?

Answer 24

1 m (3 feet).

Question 25

What is the gravel in a septic tranches main purpose?

Answer 25

Oxygen permeation.

Question 26

A septic tank uses a subsurface disposal field to distribute effluent evenly. A trench is dug in order to lay the disposal field piping. How much backfill (including both aggregate and porous soil) should be placed over the piping in order for oxygen to reach the effluent?

Answer 26

Aggregate - 6”

Porous soil - 6-24”

Question 27

If a condensing boiler or furnace is attached to a septic system, what pH range should the water be neutralized to?

Answer 27

pH of 6 to 9.