The TSURUMI 50PNI2.75S is a submersible vortex resin sewage pump from Tsurumi's PNI series, with a 50 mm discharge and a 0.75 kW 2-pole single-phase motor. It combines part-specific glass-fibre-reinforced resins with a 304 stainless steel motor frame, so it is compact, light (9.3 kg dry, excluding cable) and corrosion-resistant. The resin semi-vortex impeller is designed for wastewater and sewage carrying small solids, with a 10 mm solids passage.
Because it is lubricated with food-grade liquid paraffin, the 50PNI2.75S suits waterfalls, fountains and koi ponds as well as household, hotel and restaurant wastewater. Its small footprint allows installation in tight spaces such as septic tanks and kitchen wastewater tanks.
Selection note: this is the standard (manual) model and has no float switch. For level-controlled start and stop, add an external float switch or control panel. Tsurumi also makes an AUTO version with a bell-shaped magnetic float and identical performance; contact us if you need it. For lighter, lower-volume duty, consider the smaller OM5 (32 mm, 0.15 kW) or its automatic version, the OMA5. These are sewage pumps, not slurry pumps, and are not suitable for sludge, sand or large solids.
Key features
- Special resins with 304 stainless steel: the impeller, casing, head cover and oil casing each use a glass-fibre-reinforced resin compounded for that part, with a 304 stainless steel motor frame. Tsurumi states this is more durable and corrosion-resistant than simple resin pumps.
- Resin semi-vortex impeller (PPO-GF20): resists wear from abrasive particles and helps the pump keep its original performance for longer.
- Dual inside mechanical seals: silicon carbide faces in an oil chamber, with Tsurumi's original Oil Lifter, which keeps the seal faces lubricated and cooled down to about 1/3 of the normal oil level.
- Food-grade liquid paraffin (ISO VG32): suitable for koi ponds, fish farms and waterfalls.
- Built-in circle thermal protector (CTP): cuts the motor circuit directly on excess heat or overcurrent.
- Anti-wicking cable entry: stops water creeping into the motor by capillary action if the cable sheath is damaged or the cable end is submerged.
- Back pull-out design: remove the bolts between the oil casing and pump casing to lift out the motor with the impeller attached, making inspection and servicing easier.
- Air release valve and removable handle: the valve in the pump casing prevents air lock, and the handle can be replaced on its own.
Applications
- Homes, hotels and restaurants: wastewater and grey-water discharge
- Basements: rainwater and seepage removal
- Small wastewater treatment facilities: transfer between tanks
- Tight spaces: septic tanks and kitchen wastewater tanks
- Water features: waterfalls, fountains, koi ponds and fish farms
Performance
At 50 Hz, the 15.7 m maximum head is the head at near-zero flow, and the 340 L/min (about 20.4 m³/h) maximum capacity is the end point of the performance curve. 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.
Technical specifications
TSURUMI 50PNI2.75S technical specifications (50 Hz)
| Item | Specification |
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| General |
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| Model | 50PNI2.75S (standard, manual operation) |
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| Series | PNI (vortex resin sewage pump) |
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| Discharge bore | 50 mm |
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| Discharge connection | Threaded oval flange |
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| Hydraulic performance |
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| Max. head (at zero flow) | 15.7 m |
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| Max. capacity (curve end point) | 340 L/min (approx. 20.4 m³/h) |
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| Solids passage | 10 mm |
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| Electrical |
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| Motor output | 0.75 kW |
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| Motor | Dry-type submersible induction motor, 2-pole, insulation class E |
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| Synchronous speed | 3,000 min⁻¹ (50 Hz) |
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| Power supply | Single-phase (voltage as per nameplate) |
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| Starting method | Capacitor run |
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| Motor protection | Built-in circle thermal protector (CTP) |
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| Seals and lubrication |
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| Shaft seal | Dual inside mechanical seals, silicon carbide faces, with Oil Lifter |
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| Lubricant | Liquid paraffin (ISO VG32), 240 ml |
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| Materials |
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| Impeller | Semi-vortex, glass-fibre-reinforced resin (PPO-GF20) |
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| Pump casing | Upper: glass-fibre-reinforced resin (ABS-GF20); lower: ABS |
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| Head cover and oil casing | PPS-(MD+GF)50 |
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| Strainer and handle | ABS |
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| Motor frame | 304 stainless steel |
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| Shaft | 403 stainless steel |
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| Liquid limits |
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| Liquid | Sewage and wastewater |
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| Liquid temperature | 0–40 °C |
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| pH | 4–10 |
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| Max. submersion depth | 20 m |
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| Dimensions and weight |
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| Dimensions (L × W × H) | 241 × 162 × 380 mm |
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| Dry weight (excl. cable) | 9.3 kg |
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| Lowest running water level | 110 mm |
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Sources: Tsurumi PNI series catalogue (IA115) and Tsurumi Europe PNI series data (50 Hz). Voltage, cable and rated current of the Hong Kong supply version are as per the nameplate and confirmation from the Hong Kong agent.
Tsurumi vortex resin sewage pump comparison
Tsurumi vortex resin sewage pump model comparison (50 Hz)
| Model | Discharge | Power | Max. head | Max. capacity | Solids passage | Operation |
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| 50PNI2.75S (this product) | 50 mm | 0.75 kW | 15.7 m | 340 L/min | 10 mm | Manual |
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| OM5 | 32 mm | 0.15 kW | 7.5 m | 185 L/min | 10 mm | Manual |
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| OMA5 | 32 mm | 0.15 kW | 7.5 m | 185 L/min | 10 mm | Automatic (cylindrical float switch) |
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Optional accessories
- Float switch or level control panel: for automatic start and stop by water level. Ask us or the Tsurumi Hong Kong agent for the correct part number.
- TOK4-P guide-rail fitting (glass-fibre resin): listed by Tsurumi Europe as an accessory for the 50PNI2.75S. The kit includes a duckfoot bend, guide hook, guide support with bolts and nuts, and a 4 m lifting chain with shackles; the guide pipe is not supplied. Ask us about Hong Kong availability.
Safety and installation
- Before connecting, check that the nameplate voltage and frequency match the site supply.
- Earth the pump and connect it through an RCD/ELCB. Electrical work must be carried out by a registered electrical worker in line with local regulations.
- Lift and lower the pump by its handle. Never lift or drag it by the power cable.
- Do not run the pump dry for long periods. The built-in thermal protector trips on overheating and resets automatically once the motor cools, so the pump may restart without warning. Always isolate the power before inspection or servicing.
- Keep the water level at or above the 110 mm lowest running water level.
- Do not pump flammable or explosive liquids, liquids above 40 °C or liquids outside pH 4–10, and do not exceed 20 m submersion. The pump is not designed for seawater, chemicals or slurry.
- If the cable sheath is damaged, stop using the pump and replace the cable. The anti-wicking cable entry is not a substitute for repair.
- Although the lubricant is food-grade liquid paraffin, this is a sewage pump and must not be used for drinking water.
Wear parts and routine checks
- Main wear parts: impeller and mechanical seals. When pumping wastewater with abrasive particles, the impeller gradually wears and flow drops.
- Check the lubricant in the oil chamber (240 ml liquid paraffin) regularly. The Oil Lifter keeps the seals lubricated when the oil level is low, but the oil still needs routine checks and topping up. If the oil is cloudy or contains water, have the shaft seals inspected promptly.
- Clean debris from the strainer and pump casing regularly to maintain flow.
