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QUESTION 2
(a) One of the purposes of a sewer gas interceptor trap is to prevent foreign objects from
entering a sewer. State another purpose.
(1 mark)
(b) Describe, in order, the effect on the discharge as it passes through a grease trap.
(3 marks)
(c) Stormwater drains within and under buildings and main internal drains shall be tested.
(i) State the maximum head to which a stormwater drain can be tested during a
hydrostatic test.
(ii) State the length of time for which the test should be maintained for any
material other than vitrified clay.
(iii) State what determines that the test has been successful.
(3 marks)
(d) From your knowledge of AS/NZS3500: Part 2 Sanitary plumbing and drainage, state the
MINIMUM size of the following drain vents.
(i) The upstream vent on any main drain.
(ii) The upstream vent on any branch drain.
(iii) The section of drain acting as a vent.
(3 marks)
Total 10 marks
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Question2
a) To prevent the passage of air or gas from the sewer into the drain.
b) A grease trap works by holding hot water and allowing it to cool down so that any fats solidify. The fat or grease then floats on the surface of the water in the trap and is removed from time to time.
c1) 6 meters at lower end and 1.5 meters at the top of the drain.
c2) 30 minutes
c3) The acceptable limit is a water loss not exceeding 2 ml per hour per mm of internal diameter per metre of pipeline length.
d1) 80mm
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(d) From your knowledge of AS/NZS3500: Part 2 Sanitary plumbing and drainage, state the
MINIMUM size of the following drain vents.
(i) The upstream vent on any main drain. 50mm
(ii) The upstream vent on any branch drain. 40mm
(iii) The section of drain acting as a vent. 65mm
(3 marks)
Total 10 marks