Drainage

Question 1

Properties of clay pipes (Advantages)

Answer 1

Advantages:

1. Inexpensive due to low cost of raw material
2. Reasonably strong in compression
3. Resistant to sewer gas, erosion, corrosion
4. Flexible joints allow minor movement
5. Easy to handle

Question 2

Properties of clay pipes (Disadvantages)

Answer 2

1. Brittle
2. Tendency to shear at manhole
3. Cannot withstand high impact loading or surcharge
4. Back filling under controlled conditions is required to prevent manage

Question 3

Concrete pipes

Answer 3

Concrete pipes are made of a mixture of fine aggregate and Portland cement, that is poured over a wire cage and compacted in steel forms

Non-pressure pipes are used for low or non-pressure applications (storm water. sewerage) and manufactured in different sizes and classes.

Pipe design is influenced by depth and width of trench, back fill material and loading.

Non pressure pipes are classified according to their proof load and ultimate load. Proof load is the load that a pipe can sustain without significant cracking. Cracking should not exceed 0.25mm in width over length of 300 mm or more when tested.
Ultimate load refers to the maximum vertical load the pipe will support when tested.

Non-pressure pipes are guided by SANS 677
Ultimate load is 25% of proof

Question 4

Private sewers

Answer 4

Sewer defined as a means of conveying sewage and stormwater collected from the drains, below the ground to the final disposal point.
Sewer owned by a single person of a group of people and maintained by them is classed as a private sewer.

Savings:

1. Total length of drainpipes required
2. Number of connections to the public sewer
3. Number of openings in the road
4. Number of inspection chambers.