The TSURUMI HSZ3.75S is the automatic version of Tsurumi's HS series portable dewatering pump (officially classed by Tsurumi Hong Kong as a submersible portable dewatering pump, automatic type). It has an 80 mm (3-inch) discharge and a 0.75 kW single-phase, capacitor-run motor. A float switch controls operation: the pump starts when the water rises to a preset level and stops when it falls to a preset level, so it needs far less attention. A urethane-rubber semi-vortex impeller and a shaft-mounted agitator let it pass solids up to 7 mm. At 16.8 kg dry (excluding cable), one person can carry and position it, making it a practical choice for level-controlled drainage on construction sites, in basement sumps and during flooding.
For sites running on 110V, the HSZ3.75S 110V version is also available.
Selection note: the HSZ3.75S has the same performance as the manual HS3.75S, with the addition of a float switch for automatic operation. If you will switch the pump on and off by hand, the HS3.75S is the alternative. The HSZ3.75S is a dewatering pump, not a sewage or slurry pump. It is not suitable for raw sewage, liquids carrying fibrous solids, or settled sludge. For more flow at lower head, consider the HSZ3.75SL (up to 580 L/min). For sand and slurry, choose the HSD2.55S slurry pump, which has a high-chrome impeller and agitator.
Key features
- Automatic operation by float switch: a single float switch starts the pump when the water rises to a preset level and stops it when the water falls to a preset level. Eliminating dry running cuts power consumption and extends service life. The float switch comes fitted to the pump.
- Semi-vortex impeller with shaft-mounted agitator: the agitator prevents the air lock that semi-vortex pumps are prone to, and solids up to 7 mm pass through.
- Side discharge with spiral casing: the external side discharge helps draw solids in and pass them through smoothly.
- Abrasion-resistant wear parts: Tsurumi rates the durability as equivalent to its three-phase dewatering pumps.
- Double inside mechanical seals: silicon carbide (SiC) faces running in an oil chamber, with Tsurumi's Oil Lifter keeping the faces lubricated and cooled down to one-third of the normal oil level.
- NBR dust seal (V-ring): helps keep grit away from the shaft seal.
- Built-in circle thermal protector (CTP): cuts the motor circuit directly on overheating or overcurrent.
- Anti-wicking cable entry: stops water creeping into the motor by capillary action if the sheath is damaged or the cable end is submerged, and prevents condensation inside the motor housing. A cable clip protects against tugging.
- Resin stand: helps prevent scratching the floor.
Applications
- Construction sites: temporary dewatering of excavations, trenches and basement digs, with level-controlled start and stop
- Buildings and facilities: removing standing water from basements and car parks
- Sumps and pits: pumping out seepage or collected water automatically as the level rises, without manual switching
- Storms and flooding: emergency drainage
Performance
The 18 m maximum head is the head at near-zero flow, and the 300 L/min (about 18 m³/h) maximum capacity is the end point of the performance curve (50 Hz), the same as the manual HS3.75S. The two do not occur together: actual flow falls as total head (static head plus hose friction loss) rises. Select the pump from the performance curve using your site's total head. If you need more flow at a lower head, consider the HSZ3.75SL (10.8 m max head, 580 L/min max capacity).
Technical specifications
TSURUMI HSZ3.75S technical specifications (50 Hz)
| Item | Specification |
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| General |
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| Model | HSZ3.75S |
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| Type | Portable dewatering pump, automatic (single-phase, submersible) |
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| Discharge bore | 80 mm (3 in) |
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| Discharge connection | Hose coupling (standard); male threaded coupling for pipe connection on special request |
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| Hydraulic performance |
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| Max. head (at zero flow) | 18 m |
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| Max. capacity (curve end point) | 300 L/min (approx. 18 m³/h) |
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| Max. solids size | 7 mm |
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| Min. water level for continuous running | 90 mm |
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| Automatic control |
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| Control | Single float switch (factory-fitted) |
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| Float operating levels | FL1 (min.) 150 mm / FL2 (max.) 475 mm |
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| Min. required space (F) | 370 mm |
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| Electrical |
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| Motor output | 0.75 kW |
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| Motor | Dry-type induction motor, 2-pole, insulation class E, continuous-duty rated |
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| Power supply | Single-phase 50 Hz (voltage as per nameplate) |
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| Starting method | Capacitor run |
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| Synchronous speed | 3,000 min⁻¹ (50 Hz) |
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| Motor protection | Built-in circle thermal protector (CTP) |
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| Seals |
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| Shaft seal | Double inside mechanical seals, silicon carbide (SiC) faces, oil-lubricated, with Oil Lifter |
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| Lubricant | Turbine oil ISO VG32, 160 mL |
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| Dust seal (V-ring) | Nitrile rubber (NBR) |
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| Materials |
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| Impeller | Semi-vortex, urethane rubber |
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| Agitator | Sintered alloy |
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| Pump casing | Ductile cast iron |
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| Shaft | 403 stainless steel |
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| Stand | Resin |
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| Liquid limits (HS series data published by Tsurumi Europe) |
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| Liquid temperature | 0–40 °C |
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| pH | 5–9 |
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| Max. dry matter | 10% |
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| Max. submersion depth | 20 m |
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| Dimensions and weight |
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| Dry weight (excl. cable) | 16.8 kg |
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| Dimensions (L × W × H) | 285 × 184 × 394 mm |
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| Cable | 5 m, PVC |
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Sources: Tsurumi single-phase portable pumps catalogue (IB101), Tsurumi Hong Kong and Tsurumi Global HSZ/HS series pages, and Tsurumi Europe HS series data (50 Hz). Tsurumi notes that published data may differ from the actual product, so obtain the delivery specification sheet before use. Voltage and rated current of the Hong Kong supply version are as per the nameplate.
HSZ series (automatic) model comparison
Tsurumi HSZ series automatic portable dewatering pump comparison (50 Hz)
| Model | Discharge | Power | Max. head | Max. capacity | Dry weight | Min. space (F) |
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| HSZ2.4S | 50 mm | 0.4 kW | 12 m | 200 L/min | 11.3 kg | 340 mm |
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| HSZ2.75S | 50 mm | 0.75 kW | 18 m | 230 L/min | 16.4 kg | 370 mm |
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| HSZ3.75S (this product) | 80 mm | 0.75 kW | 18 m | 300 L/min | 16.8 kg | 370 mm |
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| HSZ3.75SL | 80 mm | 0.75 kW | 10.8 m | 580 L/min | 19.6 kg | 350 mm |
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Optional accessories
- 80 mm (3-inch) discharge hose for the standard hose coupling. Choose the length to suit your total head and discharge distance.
- Male threaded coupling for pipe connection, available from Tsurumi on special request.
Safety and installation
- Use a single-phase 50 Hz supply whose voltage matches the nameplate, properly earthed. An outlet with earth-leakage (RCD) protection is recommended, and electrical connection should be made by a registered electrical worker in line with local regulations. Never run a 110V unit on 230V or the reverse.
- Make sure the float can move up and down freely and cannot catch on the cable, the sump wall or debris. Allow at least the minimum required space (F) of 370 mm in the sump and install to the FL1/FL2 float operating levels.
- Lift and lower the pump by its handle. Never lift or drag it by the cable, and protect the cable from damage. A damaged cable must be replaced or repaired.
- For continuous running, keep the water level at 90 mm or above. The built-in CTP is a safeguard, not a reason to run the pump dry.
- Stand the pump on firm ground or a platform so it does not sink into silt.
- Do not use in flammable or explosive atmospheres, or with flammable or corrosive liquids. The standard model is not seawater-resistant and is not recommended for long-term use in seawater or brackish water. Stay within 0–40 °C and pH 5–9.
- Always isolate the power before inspection or servicing.
Wear parts and routine checks
- Main wear parts: impeller, agitator, mechanical seals and V-ring dust seal. With long running in sandy water, the impeller gradually wears and flow drops.
- Check and change the seal oil (turbine oil ISO VG32, 160 mL) periodically. The Oil Lifter only maintains lubrication down to one-third of the normal oil level; if the oil is cloudy or contains water, have the shaft seals inspected promptly.
- Clear debris from around the float regularly and confirm that the float switch starts and stops the pump correctly.
- Regularly check the cable sheath and cable entry for damage.
