Technical Booklet N Drainage·Page 28·3.15
Drain Watertightness Testing Requirements
Drains with diameter less than 300 mm must pass watertightness tests using either water pressure or air loss methods, with specific acceptance criteria for each method.
A drain of diameter less than 300 mm should be capable of withstanding a test either –
(a) by water to a pressure equal to 1.5 m head of water measured above the invert at the top of the drain; or
(b) by air to a maximum loss of head on a manometer, in a period of 5 minutes, of 25 mm for a 100 mm gauge, or 12 mm for a 50 mm gauge.
Source — /Users/richardhill/Documents/planning-arch-project/data/documents/regional/Technical Booklet N - Drainage.pdf