Sewers & Septic Systems

Question 1

What is the typical grade for the inlet and outlet of septic tanks?

Answer 1

inlet/influent -> 1/4” per foot

outlet/effluent -> 1/8” per foot

Question 2

When a pipe trench soil is hard pan or unyielding in general, the trench should be overexcavated approximately how many inches?

Answer 2

4 inches

Question 3

What tests can be used on sanitary and storm sewer lines?

Answer 3

infiltration and exfiltration

Question 4

What is the minimum septic tank cover for average and cold climates?

Answer 4

a minimum 1 foot cover in average climates or 2 feet in cold climates

Question 5

When the septic tank is above the leach field, the leader to leach lines is run at what down angle?

Answer 5

45 degrees

Question 6

A minimum septic tank size is approximately how many gallons?

Answer 6

1,000 gallons

Question 7

There should not be more than how many feet of open trench in which the line has not been completed?

Answer 7

200 feet for sanitary and sewer

Question 8

Ditch bottoms for storm drainage systems should measure how wide?

Answer 8

8 feet

Question 9

What is a combination of both tank and a drain field?

Answer 9

Cesspool

Question 10

Exfiltration tests for storm drains shall indicate leakage of no more than ___ gal/hr per inch of diameter per 100 feet of pipe.

Answer 10

1.0 gal/hr

Question 11

A natural drainage course is referred to as a?

Answer 11

Swale

Question 12

What allows the soil to drain between applications?

Answer 12

Periodic dosing of large volumes of effluent improves dain field performance

Question 13

What is a liquid limit?

Answer 13

Is the water content expressed as a percentage of the dry weight at which the soil will start to flow when testing by the shake method.

Question 14

The compartments of a three compartment tank are divided on the basis of what ratio?

Answer 14

2:1:1

Question 15

Upon approval of local authorities, the tank size and its associated leach field maybe reduced without reducing efficiency or safety by?

Answer 15

Segregating water flows

Question 16

The septic tank must be large enough to hold how many days of sewage?

Answer 16

3 - 5 days

Question 17

What is the plastic limit?

Answer 17

Is the percentage of moisture content at which the soil begins to crumble when it is rolled into a thread.

Question 18

When setting the tank, what must be observed?

Answer 18

Be sure that the inlet and oulet match-up with their corresponding pipelines.

Question 19

When plastic drain pipe is solvent welded, backfilling shoud be delayed approximately how many minutes to allow the cement to take initial set?

Answer 19

5 minutes

Question 20

How much lower than the frost line should pipe be set in a ditch?

Answer 20

2 feet

Question 21

If a polyethylene sleeve is used over ductile iron pipe, it should be taped or strapped at what intervals?

Answer 21

Every 2’ - minimize space between wrap and pipe

Question 22

The time it takes to cut ductile iron pipe with a cut off saw is?

Answer 22

1 inch per minute

Question 23

A two compartment tank is divided based on why fraction?

Answer 23

First Chamber = 2/3L

Second Chamber = 1/3L

Question 24

The septic tank sewage treatment must retain the effluent in the septic tank for at least how many hours?

Answer 24

30

Question 25

Frequency of pumping to remove solids in a septic tank?

Answer 25

3-5 years or when the combined scum and sludge layers exceed 1/3 of the tank’s depth

Question 26

Most drain fields have the drain pipe installed on a what thickness and what size rock/crushed stone? Then the cover thickness?

Answer 26

Installed on a 6” layer with 3/4” sized stone and covered with a 2” layer.

Question 27

What is a Wisconsin or Sand Mound System?

Answer 27

Placing a permeable soul mound on top of the natural soil surface and requires a pumping station to pump the tank effluent up to the sand mound.

Question 28

What is a seepage pit or drywell?

Answer 28

A perforated or open jointed lining which allows septic tank discharge to seep into the surrounding soil. Typically surrounded by gravel or crushed stone and can be up to 35 feet deep.

Question 29

Required slope or grade of a sewer pipeline?

Answer 29

5/16 inch per 10 feet or

Large pipeline => 0.01%
Small pipeline (8” and below) => 0.24%

Question 30

What is an average stone bedding requirement for pipe?

Answer 30

6-12” stone bed beneath pipe and perhaps a cover or to the spring line.