Drainage Pipe Sizing
PROSize sanitary drain pipes by fixture unit loading and minimum grade per AS/NZS 3500.2 or IPC.
BEng Mechanical Engineering (Hons), CMIOSH, LEEA Member
Mechanical engineer and certified lifting equipment examiner with 18 years in heavy industry, structural steelwork, and crane operations across construction and resources sectors.
1 April 2025
Professional verification required
These calculations are provided for estimation and educational purposes only. Results must be verified by a suitably qualified and licensed engineer before use in any design, specification, or construction context. Numly accepts no liability for decisions made on the basis of these results.
Branch drains: minimum DN 65 for WC; main drain from Table 5.1 (DFU vs pipe size). Min grade 1:60 for DN 100; 1:80 for DN 150.
Standards New Zealand
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