F2 - Groundwater Drainage - LT #4

Question 1

What is the main reason to place two 45 degree elbows at corners of drain pipe?

Answer 1

Two 45 degree elbows at corners of drain pipe speed the flow of water.

Question 2

Why is flexible pipe typically not used?

Answer 2

Deterioration over time and being crushed by backfill.

Question 3

Why is a Y branch preferable to a T joint?

Answer 3

Y branch preferable to T joint because: Waterflows freely, easier to clean out.

Question 4

How frequently are cleanouts installed?

Answer 4

Cleanouts are frequently installed at: At ends of every drainage line, where there are multiple bends that might cause blockage, and at intervals of 24 m along the length.

Question 5

What is the minimum diameter of a perimeter drain pipe?

Answer 5

100 MM minimum diameter of perimeter drain pipe.

Question 6

Purpose of filter cloth?

Answer 6

Purpose of filter cloth: Prevent backfill from filling drain rocks with sediments

Question 7

Damp, wet or flooded crawl spaces are the result of:

Answer 7

Improperly installed drainage systems, this often creates high interior humidity levels that lead to mold growth and decay.

Question 8

BCBC requires the bottom of every exterior foundation be:

Answer 8

Be drained.

Question 9

What is a perimeter drainage system?

Answer 9

Drain tile, or pipe installed at the footing level around the outside of building.

Question 10

Perimeter drain pipe for residential construction is typ. :

Answer 10

4 inch diameter and perforated with two rows of holes.

On Larger sites, Engineer will size pipe based on anticipated maximum water volumes.

Question 11

Drain pipe must be installed how?

Answer 11

Holes facing down, this prevents the pipe from silting up with sediment.

Can be installed level or slopping as long as it leads away from building.

Question 12

Pipes are glued together with:

Answer 12

PVC cement

Question 13

90 degree corners for perimeter drain made up how?

Answer 13

Two 45 fittings rather than a long sweep 90 degree.

Allowing enter to flow more quickly.

Question 14

What is a cleanout (perimeter drain)

Answer 14

Installed at or just above finished grade to allow drainage system to be maintained.

Cleanout should be installed at the ends of every drainage line where there are multiple bends that might cause blockage, and at intervals of 25 m along length of the drain.

Question 15

Once perimeter drain is installed, it is covered with:

Answer 15

Enough drain rock to form a 150 mm (6”) thick coverage over the pipe.

Question 16

What is a curtain drain?

Answer 16

Similar to a perimeter drain, made of perforated pipe surrounded by gravel. Gravel or aggregate material of a French drain is open to the surface grade to collect water.

Question 16

Where does Rainwater from the eaves troughs of a building go?

Answer 16

Routed to the storm sewer via rainwater leaders (downspouts). Rainwater leader enters a tight pipe at or slightly above finished grade and is connected to the storm sewer below the perimeter.

Question 17

How is water from a perimeter or granular drainage system disposed of?

Answer 17

Drain to a municipal storm sewer or ditch.

Question 18

What is a drywell?

Answer 18

Large pit filled with rocks. It may also be constructed using perforated well rings set on a drainage layer.

Bottom of the drywell must be above the water table, and it must be at least 5 meters away from the building and located so that the drainage from it is away from the buildings and sewage disposal system.

Question 19

How does surface water around a building need to be maintained?

Answer 19

Surface water needs to flow away from the building, the best solution is to construct the top of the foundation high enough so that the backfill can be sloped away from the building on all sides: