Dewatering keeps an excavation, trench, basement dig or quarry pit dry enough to work in. The pumps that do it run for long hours in water carrying sand, silt and grit, often from a generator, so they're built heavier than a household drainage pump.
The dewatering pumps PSA stocks are the Hyjet HBZ series: three phase submersible pumps with a 100mm discharge, listed for civil works, mining, quarrying, slurry handling, sewage treatment and general heavy pumping.
The four models
| Model | Motor | Supply | Discharge | Price |
|---|---|---|---|---|
| HBZ100.55.3 | 5.5kW | 415V 3 phase | 100mm | $5,352.55 |
| HBZ100.75.3 | 7.5kW | 415V 3 phase | 100mm | $6,942.05 |
| HBZ100.110.3 | 11kW | 415V 3 phase | 100mm | $9,257.55 |
| HBZ100.150.3 | 15kW | 415V 3 phase | 100mm | $10,990.05 |
Per the listings, the series covers up to 105 m³/h and up to 56m head between the four models. Each has a copper-wound Class B IP68 motor, a maximum liquid temperature of 40°C, a maximum immersion of 25m and a 20m cable. The flow and head of each individual model are on its pump curve in the datasheet under Downloads.
What to work out first
- Inflow rate. How fast water is coming into the excavation, from groundwater seepage and rain. The pump has to beat it with a margin. A geotechnical report or a short pump test on site gives the best number.
- Total head. The vertical lift from the water level in the sump to the discharge point, plus friction in the discharge hose or pipe. Long runs of layflat hose add more friction than people expect.
- Read the curve. Pick the model whose curve delivers your flow at your total head. Don't size from the series maximums, which aren't reached by a single pump at the same time.
Power supply
All four HBZ models are 415V three phase. On a construction site that usually means a temporary three phase supply or a generator. Size a generator for the motor's starting current, not just its running kW: a direct-on-line start draws several times the running current for a moment. A pump controller with a soft starter reduces that starting load. A licensed electrician must connect three phase equipment.
On site
- Sump the pump. Sit the pump in a sump or on a firm base so it isn't drawing straight from loose sand and mud, which wears the impeller and can bury the inlet.
- Keep it covered. Don't let the pump run with the motor out of water for long; check the datasheet for its cooling requirements.
- Where the water goes. Discharging dewatering water to stormwater usually needs approval, and sediment-laden water often has to be treated or settled first. Check your local council and EPA requirements before you start pumping.
- Use the cable to lift? Don't. Lift and lower the pump by its handle with a rope or chain, never by the power cable.
For smaller jobs and dirty water with solids, see the vortex pumps, including the Hyjet DG range listed for construction dewatering. The HBZ range is available to order on backorder; contact PSA to confirm lead time.
Frequently Asked Questions
What flow and head do Hyjet HBZ dewatering pumps reach?
Across the four models, the series is listed at up to 105 m³/h and up to 56m head. Check each model's pump curve in the datasheet for its exact performance.
Can I run an HBZ dewatering pump on single phase?
No. All four HBZ models are 415V three phase, so you need a three phase supply or a suitably sized generator.
How do I size a generator for a dewatering pump?
Allow for the motor's starting current, which is several times its running current on a direct start. A soft starter reduces the starting load.
Can I discharge dewatering water into the stormwater drain?
Usually only with approval, and sediment-laden water often has to be settled or treated first. Check with your local council and EPA.