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Hydronic Pipe Size Calculator

NCC 2022 Section J — Part J6D8 · Copper Type B & Mild Steel Schedule 40 · DN15–DN350 · Colebrook-White friction method

01System Type

6°C · ρ 999.8 kg/m³ · μ 1.307×10⁻³ Pa·s

02Pipe Material

ε Copper: 0.0015 mm · Steel: 0.046 mm

03Distribution Type

Non-dist: same flow throughout. Dist: branched network.

04Flow Control

Operating Parameters

Steps 05 – 06

05Yearly Operating Hours

06Water Flow Rate

Litres per second ( L/s )

NCC J6D8 — Table J6D8d — Distributive, Variable Speed

Limits are pipe-diameter-specific — highlighted row = selected pipe result — n/a = band not in this table

Pa/m

Nominal DN (mm)	≤5,000 hrs/yr	>5,000 hrs/yr
DN 15	400	250
DN 20	400	250
DN 25	400	180
DN 32	400	180
DN 40	400	180
DN 50	400	180
DN 65	400	300
DN 80	400	300
DN 100	400	300
DN 125	400	300
DN 150	400	300
DN 200	400	300
DN 250	400	300
DN 300	400	300
DN 350	400	300

NCC J6D8(4) applies to straight pipe segments along the index run only. Valves and fittings are excluded per J6D8(5)(a). Where the smallest compliant pipe gives ≤0.7 m/s, the pressure drop requirement does not apply per J6D8(5)(b). Velocity guideline: 0.7–3.0 m/s typical practice. This calculator provides guidance only and does not replace professional engineering judgement. Contact True Partners Consulting Engineers for project-specific advice.

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Select parameters and enter a flow rate, then tap Run Calculation