Which formula is used for HDPE pipe head loss?

Hazen-Williams with a roughness coefficient C of 145 for polyethylene. For tighter work, or for fluids other than water, Darcy-Weisbach with a computed friction factor is the better basis.

Why are several diameters offered for one flow rate?

Because diameter selection is a trade. A larger bore cuts head loss and pumping energy but costs more in pipe. The tool shows every option with its velocity and loss so the trade is visible.

Is the calculated pump power the motor I should buy?

No. It is an estimate from total head and flow with a reserve applied. Final motor selection has to come from the pump curve, the real efficiency at the duty point and the starting conditions.

Does it check for surge?

No. Surge needs a separate calculation and depends on valve closure speed, line length and flow velocity. On long lines or at higher velocities, check it separately.

BUKAN PIPE

Pipeline Design Calculator

Pre-design tool for water transfer networks.

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This tool supports preliminary design of water transfer lines from source to destination. Results do not replace engineering calculation with actual elevation profile and pump curves.

What the inputs mean

Flow rate — the volume to be moved per unit time
Route length — the real pipe length, not the straight-line distance on a map
Elevation difference — the lift the pump has to overcome
SDR and PN — the pipe class, which sets wall thickness and therefore the bore

What the calculation rests on

Friction head loss uses Hazen-Williams with a roughness coefficient C of 145 for polyethylene — the smooth bore of PE is what justifies a value that high. Total head is the elevation difference plus friction loss, and motor power follows from total head and flow rate with a reserve percentage applied.

Why velocity is the constraint

The tool computes velocity for each candidate diameter and flags anything outside roughly 0.5 to 2.5 m/s. Below 0.5 there is a risk of suspended solids settling out. Above 2.5, head loss climbs quickly, pumping energy gets expensive and surge on rapid valve closure becomes a more serious concern. The recommended diameter is the smallest one that keeps velocity inside that band.

What it does not calculate

The real elevation profile and any high points along the route
The pump curve and its actual duty point
Surge and transient pressure
Local losses at fittings, valves and bends
Temperature derating above the 20 °C reference

From result to order

The output is an effective internal diameter and a pipe class. To enquire, take the outer diameter and SDR from the catalogue dimensions chart and quote those. If the operating temperature is above 20 °C, apply the derating factor before fixing the SDR.

FAQ

Which formula is used for HDPE pipe head loss?: Hazen-Williams with a roughness coefficient C of 145 for polyethylene. For tighter work, or for fluids other than water, Darcy-Weisbach with a computed friction factor is the better basis.
Why are several diameters offered for one flow rate?: Because diameter selection is a trade. A larger bore cuts head loss and pumping energy but costs more in pipe. The tool shows every option with its velocity and loss so the trade is visible.
Is the calculated pump power the motor I should buy?: No. It is an estimate from total head and flow with a reserve applied. Final motor selection has to come from the pump curve, the real efficiency at the duty point and the starting conditions.
Does it check for surge?: No. Surge needs a separate calculation and depends on valve closure speed, line length and flow velocity. On long lines or at higher velocities, check it separately.

Preliminary water transfer line estimate — well depth (20 m) is excluded from total head. Total head equals vertical lift (150 m) plus line friction loss.

Hazen-Williams C = 145 for PE pipe
Pump efficiency = 0.75
Well depth excluded from total head

Vertical lift to destination (m)Flow rate (m³/h)Pipe length (m)SDRPNMotor power reserve (%)Pipe gradeExternal diameter (mm) — comma-separated

Preliminary recommendation: External diameter 90 mm — velocity 0.65 m/s — total head 464090.1 m — power 19391.23 kW

Results

OD mm	SDR	PN	e mm	ID mm	v m/s	hf m	H m	kW	Status
32	11	16	1.45	26.18	5.16	71448251.49	71448401.49	2985352.38	High velocity
40	11	16	1.82	32.73	3.30	24095887.77	24096037.77	1006812.78	High velocity
50	11	16	2.27	40.91	2.11	8126326.33	8126476.33	339551.27	OK
63	11	16	2.86	51.55	1.33	2636266.63	2636416.63	110158.28	OK
75	11	16	3.41	61.36	0.94	1127596.54	1127746.54	47121.01	OK
90	11	16	4.09	73.64	0.65	463940.07	464090.07	19391.23	OK
110	11	16	5.00	90.00	0.44	174563.48	174713.48	7300.11	Low velocity
125	11	16	5.68	102.27	0.34	93654.46	93804.46	3919.46	Low velocity
140	11	16	6.36	114.55	0.27	53924.67	54074.67	2259.42	Low velocity
160	11	16	7.27	130.91	0.21	28139.00	28289.00	1182.01	Low velocity
180	11	16	8.18	147.27	0.16	15854.22	16004.22	668.71	Low velocity
200	11	16	9.09	163.64	0.13	9489.87	9639.87	402.79	Low velocity
225	11	16	10.23	184.09	0.10	5346.83	5496.83	229.68	Low velocity
250	11	16	11.36	204.55	0.08	3200.45	3350.45	139.99	Low velocity
280	11	16	12.73	229.09	0.07	1842.77	1992.77	83.26	Low velocity
315	11	16	14.32	257.73	0.05	1038.26	1188.26	49.65	Low velocity
355	11	16	16.14	290.45	0.04	579.98	729.98	30.50	Low velocity
400	11	16	18.18	327.27	0.03	324.30	474.30	19.82	Low velocity
450	11	16	20.45	368.18	0.03	182.72	332.72	13.90	Low velocity
500	11	16	22.73	409.09	0.02	109.37	259.37	10.84	Low velocity
560	11	16	25.45	458.18	0.02	62.97	212.97	8.90	Low velocity
630	11	16	28.64	515.45	0.01	35.48	185.48	7.75	Low velocity

Results are for preliminary design only and do not replace verified engineering calculations. Final pump and pipe selection must consider pump curves, operating pressure and the actual elevation profile.