How to Size and Select a WQ Submersible Sewage Pump Without Over-Engineering?

Sizing a submersible sewage pump isn’t just about picking a motor horsepower ( $HP$ ) off a shelf. Over-sizing a pump leads to excessive energy consumption, frequent cycling, rapid wear on mechanical seals, and water hammer. Under-sizing leads to clogging, overheating, and system flooding.

Follow this systematic guide to size your WQ series submersible pump accurately for wet well lift stations.

Step 1: Determine the Required Flow Rate ( $Q$ )

Your required flow rate depends on the peak inflow rate entering the sump pit.

Municipal Lift Stations: Flow is calculated based on peak hourly fixture units (GPM or $\text{m}^3/\text{h}$ ).
Stormwater Sump Pits: Calculated using local rainfall intensity data and drainage surface area.
Rule of Thumb: Design the pump flow rate ( $Q$ ) to be $1.2\text{--}1.5$ times the peak incoming flow rate to allow for periodic drawdown of the wet well.

Step 2: Calculate Total Dynamic Head ( $TDH$ )

Total Dynamic Head is the total equivalent height the pump must lift the fluid, combining static elevation and friction losses.

\text{TDH} = \text{Static Head} + \text{Friction Head Loss}

Static Head: The vertical distance from the lowest liquid level in the sump (pump cut-off level) to the highest point of discharge piping.
Friction Head Loss: Calculate pipe wall friction across total pipe length, plus fitting losses (elbows, check valves, gate valves, and reducers). Use the Hazen-Williams equation or standard equivalent pipe length charts.

Engineering Tip: Always maintain a flow velocity of $0.7\text{--}1.5\text{ m/s}$ ( $2.3\text{--}5\text{ ft/s}$ ) in the discharge pipe to keep solids in suspension and prevent pipe settling without causing extreme pipe erosion.

Step 3: Evaluate Fluid Characteristics and Operating Duty

Standard cast iron (HT200/HT250) WQ pumps perform reliably in neutral municipal wastewater ( $\text{pH } 6\text{--}9$ ). However, chemical or industrial sumps require material upgrades:

Corrosive Effluent ( $\text{pH } < 5$ or High Chlorine): Upgrade to 304 or 316 Stainless Steel casing and impeller.
Abrasive Mining or Sand Slurry: Select High-Chrome Alloy (Cr27+) impellers to resist erosion.
Continuous Duty: Ensure the motor is rated for $S1$ continuous operation, featuring Class F or Class H insulation.

Quick Selection Formula Sheet

WQ Submersible Sewage Pump Technical Data:

Discharge (MM)	Pump Model	Capacity (m³/h)	Head (m)	Power (kw)	Voltage (V)	Speed (r/min)	Pipe discharg (inch)
25	25WQ5-20-0.75	5	20	0.75	380	2900	1
32	32WQ6-18-0.75	6	18	0.75	380	2900	1.2
40	40WQ7-15-0.75	7	15	0.75	380	2900	1.5
50	50WQ10-10-0.75	10	10	0.75	380	2900	2
65	65WQ15-7-0.75	15	7	0.75	380	2900	2.5
25	25WQ5-22-1.1	5	22	1.1	380	2900	1
32	32WQ6-20-1.1	6	20	1.1	380	2900	1.2
40	40WQ7-18-1.1	7	18	1.1	380	2900	1.5
50	50WQ10-12-1.1	10	12	1.1	380	2900	2
65	65WQ15-9-1.1	15	9	1.1	380	2900	2.5
50	50WQ10-16-1.5	10	16	1.5	380	2900	2
65	65WQ20-10-1.5	20	10	1.5	380	2900	2.5
80	80WQ40-7-1.5	40	7	1.5	380	2900	3
100	100WQ50-5-1.5	50	5	1.5	380	2900	4
50	50WQ9-22-2.2	9	22	2.2	380	2900	2
65	65WQ20-15-2.2	20	15	2.2	380	2900	2.5
80	80WQ40-10-2.2	40	10	2.2	380	2900	3
100	100WQ50-7-2.2	50	7	2.2	380	2900	4
50	50WQ15-25-3	15	25	3	380	2900	2
65	65WQ25-18-3	25	18	3	380	2900	2.5
80	85WQ45-12-3	45	12	3	380	2900	3
100	100WQ60-9-3	60	9	3	380	2900	4
50	50WQ15-30-4	15	30	4	380	2900	2
65	65WQ25-25-4	25	25	4	380	2900	2.5
80	80WQ40-16-4	40	16	4	380	2900	3
100	100WQ60-12-4	60	12	4	380	2900	4
50	50WQ15-40-5.5	15	40	5.5	380	2900	2
65	65WQ25-30-5.5	25	30	5.5	380	2900	2.5
80	80WQ40-22-5.5	40	22	5.5	380	2900	3
100	100WQ60-18-5.5	60	18	5.5	380	2900	4
150	150WQ100-7-5.5	100	7	5.5	380	2900	6
50	50WQ20-45-7.5	20	45	7.5	380	2900	2
65	65WQ30-35-7.5	30	35	7.5	380	2900	2.5
80	80WQ40-28-7.5	40	28	7.5	380	2900	3
100	100WQ65-22-7.5	65	22	7.5	380	2900	4
150	150WQ100-12-7.5	100	12	7.5	380	2900	6
50	50WQ20-55-11	20	55	11	380	2900	2
65	65WQ30-40-11	30	40	11	380	2900	2.5
80	80WQ60-30-11	60	30	11	380	2900	3
100	100WQ80-25-11	80	25	11	380	2900	4
150	150WQ100-20-11	100	20	11	380	2900	6
150	150WQ120-15-11	120	15	11	380	2900	6
200	200WQ180-11-11	180	11	11	380	2900	8
50	50WQ20-70-15	20	70	15	380	2900	2
65	65WQ30-60-15	30	60	15	380	2900	2.5
80	80WQ60-40-15	60	40	15	380	2900	3
100	100WQ80-35-15	80	35	15	380	2900	4
150	150WQ100-30-15	100	30	15	380	2900	6
150	150WQ120-25-15	120	25	15	380	2900	6
200	200WQ180-15-15	180	15	15	380	2900	8
50	50WQ20-80-18.5	20	80	18.5	380	2900	2
65	65WQ30-68-18.5	30	68	18.5	380	2900	2.5
80	80WQ60-45-18.5	60	45	18.5	380	2900	3
100	100WQ80-40-18.5	80	40	18.5	380	2900	4
150	150WQ100-36-18.5	100	36	18.5	380	2900	6
200	200WQ180-18-18.5	180	18	18.5	380	2900	8
50	50WQ20-90-22	20	90	22	380	2900	2
65	65WQ30-75-22	30	75	22	380	2900	2.5
80	80WQ60-50-22	60	50	22	380	2900	3
100	100WQ80-45-22	80	45	22	380	2900	4
150	150WQ100-40-22	100	40	22	380	2900	6
200	200WQ200-20-22	200	20	22	380	2900	8
80	80WQ80-13-5.5	80	13	5.5	380	1450	3
100	100WQ110-10-5.5	110	10	5.5	380	1450	4
150	150WQ150-7-5.5	150	7	5.5	380	1450	6
80	80WQ80-20-7.5	80	20	7.5	380	1450	3
100	100WQ100-15-7.5	100	15	7.5	380	1450	4
150	150WQ145-9-7.5	145	9	7.5	380	1450	6
200	200WQ250-6-7.5	250	6	7.5	380	1450	8
100	100WQ100-25-11	100	25	11	380	1450	4
150	150WQ180-11-11	180	11	11	380	1450	6
200	200WQ300-7-11	300	7	11	380	1450	8
250	250WQ400-5-11	400	5	11	380	1450	10
100	100WQ100-30-15	100	30	15	380	1450	4
150	150WQ200-15-15	200	15	15	380	1450	6
200	200WQ250-11-15	250	11	15	380	1450	8
250	250WQ500-5-15	500	5	15	380	1450	10
100	100WQ100-35-18.5	100	35	18.5	380	1450	4
150	150WQ180-20-18.5	180	20	18.5	380	1450	6
200	200WQ250-15-18.5	250	15	18.5	380	1450	8
200	200WQ350-10-18.5	350	10	18.5	380	1450	8
250	250WQ500-7-18.5	500	7	18.5	380	1450	10
300	300WQ650-5-18.5	650	5	18.5	380	1450	12
100	100WQ100-40-22	100	40	22	380	1450	4
150	150WQ200-22-22	200	22	22	380	1450	6
200	200WQ300-16-22	300	16	22	380	1450	8
200	200WQ400-10-22	400	10	22	380	1450	8
250	250WQ500-9-22	500	9	22	380	1450	10
300	300WQ650-7-22	650	7	22	380	1450	12
100	100WQ120-45-30	120	45	30	380	1450	4
150	150WQ180-30-30	180	30	30	380	1450	6
200	200WQ250-22-30	250	22	30	380	1450	8
250	250WQ500-12-30	500	12	30	380	1450	10
250	250WQ600-9-30	600	9	30	380	1450	10
300	300WQ800-7-30	800	7	30	380	1450	12
300	300WQ1000-6-30	1000	6	30	380	980	12
350	350WQ1500-4-30	1500	4	30	380	980	14
100	100WQ120-50-37	120	50	37	380	1450	4
150	150WQ200-35-37	200	35	37	380	1450	6
200	200WQ300-28-37	300	28	37	380	1450	8
200	200WQ350-25-37	350	25	37	380	1450	8
250	250WQ600-12-37	600	12	37	380	1450	10
300	300WQ800-9-37	800	9	37	380	1450	12
350	350WQ1000-6-37	1000	6	37	380	1450	14
350	350WQ1100-6-37	1100	6	37	380	980	14
400	400WQ1300-5-37	1300	5	37	380	980	16
100	100WQ100-57-45	100	57	45	380	1450	4
150	150WQ200-40-45	200	40	45	380	1450	6
200	200WQ300-32-45	300	32	45	380	1450	8
200	200WQ400-25-45	400	25	45	380	1450	8
250	250WQ600-15-45	600	15	45	380	1450	10
300	300WQ800-12-45	800	12	45	380	1450	12
350	350WQ1200-8-45	1200	8	45	380	1450	14
350	350WQ1300-8-45	1300	8	45	380	980	14
400	400WQ1700-6-45	1700	6	45	380	980	16
100	100WQ100-65-55	100	65	55	380	1450	4
150	150WQ180-50-55	180	50	55	380	1450	6
200	200WQ300-40-55	300	40	55	380	1450	8
200	200WQ400-30-55	400	30	55	380	1450	8
250	250WQ600-20-55	600	20	55	380	1450	10
300	300WQ800-15-55	800	15	55	380	1450	12
350	350WQ1000-10-55	1000	10	55	380	1450	14
350	350WQ1100-10-55	1100	10	55	380	980	14
400	400WQ1300-8-55	1300	8	55	380	1450	16
400	400WQ1500-8-55	1500	8	55	380	980	16
500	500WQ2200-5-55	2200	5	55	380	740	20
100	100WQ120-75-75	120	75	75	380	1450	4
150	150WQ200-60-75	200	60	75	380	1450	6
200	200WQ350-45-75	350	45	75	380	1450	8
250	250WQ600-25-75	600	25	75	380	1450	10
300	300WQ800-20-75	800	20	75	380	1450	12
350	350WQ1000-15-75	1000	15	75	380	1450	14
350	350WQ1500-12-75	1500	12	75	380	980	14
400	400WQ1300-13-75	1300	13	75	380	1450	16
400	400WQ1700-10-75	1700	10	75	380	980	16
500	500WQ2000-8-75	2000	8	75	380	980	20
500	500WQ2700-6-75	2700	6	75	380	740	20
100	100WQ120-85-90	120	85	90	380	1450	4
150	150WQ200-70-90	200	70	90	380	1450	6
200	200WQ300-60-90	300	60	90	380	1450	8
200	200WQ400-50-90	400	50	90	380	1450	8
250	250WQ600-30-90	600	30	90	380	1450	10
300	300WQ800-25-90	800	25	90	380	1450	12
350	350WQ1000-18-90	1000	18	90	380	1450	14
350	350WQ1200-18-90	1200	18	90	380	980	14
400	400WQ1300-16-90	1300	16	90	380	1450	16
400	400WQ1500-15-90	1500	15	90	380	980	16
500	500WQ2000-10-90	2000	10	90	380	980	20
500	500WQ2500-8-90	2500	8	90	380	740	20
600	600WQ3000-6-90	3000	6	90	380	740	24
100	100WQ100-100-110	100	100	110	380	1450	4
150	150WQ180-80-110	180	80	110	380	1450	6
200	200WQ300-65-110	300	65	110	380	1450	8
250	250WQ600-40-110	600	40	110	380	1450	10
300	300WQ1000-25-110	1000	25	110	380	1450	12
350	350WQ1300-20-110	1300	20	110	380	1450	14
350	350WQ1600-16-110	1600	16	110	380	980	14
400	400WQ1500-17-110	1500	17	110	380	1450	16
400	400WQ1800-15-110	1800	15	110	380	980	16
500	500WQ2500-10-110	2500	10	110	380	980	20
500	500WQ3000-8-110	3000	8	110	380	740	20
600	600WQ3200-7-110	3200	7	110	380	980	24
600	600WQ3800-6-110	3800	6	110	380	740	24
150	150WQ200-90-132	200	90	132	380	1450	6
200	200WQ400-75-132	400	75	132	380	1450	8
250	250WQ500-50-132	500	50	132	380	1450	10
300	300WQ800-36-132	800	36	132	380	1450	12
350	350WQ1100-28-132	1100	28	132	380	1450	14
350	350WQ1500-20-132	1500	20	132	380	980	14
400	400WQ1700-16-132	1700	16	132	380	1450	16
400	400WQ2000-15-132	2000	15	132	380	980	16
500	500WQ2800-10-132	2800	10	132	380	980	20
500	500WQ3100-10-132	3100	10	132	380	740	20
600	600WQ3700-8-132	3700	8	132	380	980	24
600	600WQ4000-8-132	4000	8	132	380	740	24