A sewage pump is a submersible pump engineered to handle raw sewage, sludge, and wastewater containing solids up to 100 mm in diameter. The CSW Series (2–200 HP) operates at specific gravity (SG) up to 1.7 and serves municipal corporations, residential complexes, and industrial effluent plants across India and 22+ export countries.
Unlike clean-water dewatering pumps, a sewage pump must pass large, irregular solids — rags, fibrous waste, soft organic matter — without clogging. The CSW Series achieves this through wide-clearance impeller geometry, a dual TC-vs-TC mechanical seal rated for abrasive media, and F-class motor insulation that tolerates the elevated temperature of dense sewage slurry.
With 100+ CSW sewage pump installations and 200+ total pumps deployed annually across municipal sewage treatment plant (STP) projects, the CSW Series represents field-tested performance across India’s most demanding municipal and industrial effluent applications.
The CSW Series covers the full range of municipal and industrial sewage pumping duty from small residential sumps to large municipal lift stations:
| Parameter | CSW Series Range | Notes |
|---|---|---|
| Shut-Off Head | 5 M – 60 M | Covers low-lift residential to high-head municipal mains |
| Flow Rate | 775 – 33,000 LPM | 13 – 550 m³/hr; selectable by HP rating |
| HP Range | 2 – 200 HP | Full submersible sewage range |
| Solids Handling | 20 – 100 mm diameter | Passes organic solids, soft rags, fibrous waste |
| Specific Gravity (SG) | Up to 1.7 | Handles dense sewage sludge; standard water SG = 1.0 |
| Impeller Material | SS / Cast Iron | SS for corrosive effluent; CI for standard municipal sewage |
| Shaft Material | SS410 (high-torsional strength) | Resists shaft deflection under heavy solids load |
| Motor Insulation | F-Class (155°C) with thermal sensor | Optional H-class (180°C) for higher ambient/fluid temps |
| Mechanical Seal | Dual TC vs TC + oil seal | Handles abrasive solids; TC = tungsten carbide |
| Bearings | Angular / Radial / Tapper ball (high-temp grease) | Extended bearing life in continuous submersible duty |
| Lifting Hook | SS316 stainless steel | Critical for wet-well retrieval without rope corrosion |
| Optional Sensors | Moisture sensor + temperature sensor | Early leak detection; prevents motor burn in unattended sites |
| Power Cable | Submersible-rated insulation | Rated for continuous wet-well immersion |
| Application | Typical Duty | CSW Model Range | Key Selection Reason |
|---|---|---|---|
| Municipal Lift Station | Continuous, 24/7 duty; high flow to gravity sewer main | 50–200 HP | High flow (up to 33,000 LPM), SG 1.2–1.4 raw sewage, 100mm solids |
| STP Inlet / Outlet Sump | Intermittent; matches influent flow to treatment stages | 20–100 HP | Consistent head, reliable low-maintenance operation at inlet screens |
| Industrial ETP / Effluent Sump | Batch or continuous; pH-variable effluent | 10–75 HP | SG tolerance up to 1.7 for dense industrial wastewater |
| Residential / Commercial Basement Sump | Intermittent; storm or blackwater overflow | 2–15 HP | Compact submersible footprint; handles solids from plumbing overflow |
| Sewage Bypass (Emergency) | Short-term; during STP maintenance or pipe repair | 15–75 HP | Portable; rapid deployment; handles raw influent load |
| Public Health Engineering — Septage Transfer | Batch; desludging of septic tanks / septage pits | 5–30 HP | 100mm solids handling for unscreened septage; SG up to 1.5 |
All three series handle solids-laden fluid, but each is optimised for a distinct duty range. Selecting the wrong series is the most common cause of premature wear and seal failure in industrial wastewater applications.
| Factor | CSW — Sewage | CNC — Non-Clog | CSL — Slurry |
|---|---|---|---|
| Max Solids Size | 100 mm (largest) | 70 mm (vortex impeller) | 70 mm (by weight fraction) |
| Max SG | 1.7 | 1.2 | 2.1 (highest) |
| HP Range | 2–200 HP | 6–20 HP | Up to 100 HP |
| Wetted Material | SS / Cast Iron | SS304 volute; SS410 impeller | 27% Hi-Chrome Iron (abrasion-resistant) |
| Primary Media | Municipal / industrial sewage, STP | Fibrous sewage, bypass, manhole cleaning | Mine slurry, ash, sand, heavy abrasives |
| Impeller Type | Wide-clearance channel | Vortex (non-contact) | Recessed / open (hi-chrome) |
| Best Application | STPs, lift stations, ETP sumps, high-rise basement | Manhole cleaning, sewage bypass | Mining, ash pond, harbour dredging, thermal plants |
| Solids Character | Large organic, soft solids, rags | Fibrous, stringy waste | Hard abrasive mineral particles |
Decision rule: If solids exceed 70 mm, or SG is 1.2–1.7 with organic sewage — choose CSW. If media is primarily fibrous (rags, wet wipes, hair) at smaller flows — choose CNC. If solids are hard mineral abrasives or SG exceeds 1.7 — choose CSL.
Correct pump sizing prevents two common failures: undersizing (overheating, cavitation) and oversizing (high velocity impeller wear, energy waste). Use this field-validated procedure for CSW selection:
For a municipal lift station or STP inlet sump, peak flow is driven by the population-equivalent (PE) discharge rate with a peak factor applied:
Q_peak = (PE × daily_per_capita_flow × Peak_Factor) ÷ (Pumping_Hours × 60)
Example: A residential STP serving 5,000 persons, 8-hour pumping: Q = (5,000 × 135 × 2.5) ÷ (8 × 60) = 1,687,500 ÷ 480 = 3,515 LPM → select CSW in the 3,500–4,000 LPM flow band.
TDH is the total resistance the pump must overcome. For sewage systems, always apply a safety factor of 1.15–1.20 over calculated TDH to account for aging pipe roughness and valve losses:
TDH = Static_Head + Friction_Head + Minor_Losses
Example: Hs = 12 m, Hf calculated = 4.5 m, minor losses = 0.5 m → TDH = (12 + 4.5 + 0.5) × 1.20 = 20.4 M design head.
Map your Q and TDH values to the CSW performance curve table. Always select the model whose Best Efficiency Point (BEP) sits within 10–15% of your duty point — operating far from BEP accelerates impeller and seal wear in abrasive sewage media:
| CSW HP | Indicative Flow Range (LPM) | Indicative Head Range (M) | Typical Application |
|---|---|---|---|
| 2 HP | 775 – 1,200 | 5 – 12 | Small residential sump, grey water sump |
| 5 HP | 1,200 – 2,500 | 8 – 18 | Commercial building, small housing colony |
| 10 HP | 2,500 – 5,000 | 10 – 25 | STP inlet sump (small); 500–1,000 PE |
| 20 HP | 5,000 – 8,500 | 12 – 30 | STP inlet (medium); ETP sump |
| 40 HP | 8,500 – 14,000 | 15 – 40 | Municipal lift station (medium) |
| 75 HP | 14,000 – 22,000 | 20 – 50 | Municipal lift station (large); STP inlet (large) |
| 100–200 HP | 22,000 – 33,000 | 25 – 60 | Major municipal STP; industrial ETP (large); combined sewer |
Request exact performance curves for your duty point — contact our hydraulic engineering team for CSW pump curve PDF and motor data sheet.
Use iDEWA AI Advisor to Size Your CSW Sewage Pump Instantly
With 100+ CSW sewage pump installations across India and 200+ pumps deployed annually in sewage rehabilitation projects, the following application data is drawn from field experience:
Municipal lift stations require continuous-duty pumps that can handle the full diurnal variation in sewage flow — from early morning peak (7–9 AM at 3× average) to overnight trough. The CSW Series 50–200 HP models are configured in duty-standby pairs, with moisture sensors and CosmoSmart IoT integration for remote monitoring of wet-well level and run-hours.
For STP inlet sumps, the CSW operates at the head of the treatment train, receiving raw, unscreened influent. The dual TC-vs-TC mechanical seal is particularly critical here — unscreened municipal influent regularly contains grit, sand, and fibrous rags that destroy standard silicon carbide seals within 6–8 months. The CSW’s tungsten carbide seals extend service intervals to 18–24 months in this duty.
Industrial effluent treatment plants (ETPs) at textile, food processing, pharmaceutical, and chemical manufacturing facilities generate dense wastewater with SG ranging from 1.2 (food processing washdowns) to 1.6–1.7 (concentrated chemical effluent before dilution). The CSW Series’ SG 1.7 tolerance and F-class motor insulation make it the preferred choice over standard drainage pumps, which are rated only to SG 1.1.
At a major textile manufacturing zone with 250+ looms, CSW 20–40 HP models handle combined process wastewater and fabric lint — a mixed solid/fluid stream that defeats conventional non-clog vortex pumps due to its combination of fibrous and soft organic solids above 70 mm.
High-rise residential towers above 20 storeys face a recurring problem: basement sump pumps encounter a mix of groundwater seepage, grey water overflow from plumbing faults, and occasionally raw sewage backflow during monsoon surcharge events. A standard 1.5 HP dewatering pump with 4–12 mm solids clearance will block immediately on the first overflow event. The CSW 2–10 HP models provide true sewage-duty protection at a compact footprint suitable for confined sump pits.
Public health engineering departments operating septage reception facilities and sewage desilting programmes require pumps that handle unscreened, high-solids content septage (SG up to 1.5, solids up to 80–100 mm). The CSW 5–30 HP range is used for batch septage transfer from collection tankers to primary treatment lagoons, where the variable duty cycle and wide solids range make any other pump series impractical.
The municipal segment page provides further detail on Cosmos Pumps’ infrastructure project experience across flood control, STP, and stormwater bypass applications.
Planned STP maintenance shutdowns and emergency sewer rehabilitation require short-term sewage bypass pumping without capital expenditure. Pump rental options are available for CSW-equivalent sewage duty across India, enabling rapid deployment for bypass campaigns of 1 day to 12 months.
iDEWA is an AI-powered hydraulic advisor that calculates peak flow, TDH, and recommended CSW model in under 2 minutes — replacing manual spreadsheet sizing for standard sewage pump applications. Input your sump dimensions, population equivalent, static head, and pipe data; iDEWA returns a detailed sizing report with performance curve match and seal recommendation.
Developed by the hydraulic engineering team at Cosmos Pumps and validated against 100+ field installations, iDEWA is available free for all EPC contractors, municipal engineers, and STP project managers.
Launch iDEWA — Free AI Sewage Pump Sizing
A drainage pump (such as the CDW series) is designed for relatively clean water with small suspended solids up to 4–12 mm diameter and specific gravity not exceeding 1.1. A sewage pump (CSW series) is built specifically to pass raw sewage containing large organic solids up to 100 mm, operate in media with SG up to 1.7, and withstand the abrasive and corrosive chemistry of untreated wastewater. The internal hydraulics differ fundamentally — sewage pumps use wide-clearance or vortex impellers, while drainage pumps use tighter-clearance designs optimised for hydraulic efficiency in clean water.
Yes — the CSW Series is rated for solids up to 100 mm in diameter. This is achieved through a wide-clearance channel impeller geometry that allows large organic solids to pass through the pump hydraulics without stringer formation or blockage. In field application, 100 mm solids passage is validated for soft organic solids (food waste, faecal matter, soft rags); hard objects such as stones, metal, or plastics above 50 mm are outside the rated duty and will cause impeller damage. Inlet bar screens at STP sumps are recommended to exclude rigid debris.
HP selection depends on peak flow and total dynamic head (TDH). For a municipal lift station serving 5,000–10,000 persons (CPHEEO standard 135 L/capita/day, peak factor 2.5), peak flow typically falls in the 3,500–7,000 LPM range. Combined with a typical TDH of 15–25 M for rising mains up to 1.5 km, this corresponds to the CSW 20–50 HP range. Lift stations serving larger populations (50,000+ PE) or requiring higher TDH (35–60 M) require 75–200 HP units. Use the 3-step sizing procedure above or the iDEWA AI Advisor for a site-specific recommendation.
Specific gravity (SG) is the ratio of fluid density to pure water density (1.0). Municipal sewage typically has an SG of 1.0–1.05; industrial effluent with dissolved solids can reach 1.2–1.5; concentrated industrial wastewater or septage can reach 1.5–1.7. Pumping fluids at SG above 1.0 increases the hydraulic power demand proportionally — a pump rated at 10 HP for SG 1.0 will require 17 HP to deliver the same flow and head at SG 1.7. Standard dewatering pumps rated only to SG 1.1 will be severely overloaded, overheating the motor within hours. The CSW Series’ mechanical design, motor winding specification, and bearing selection are all calibrated for continuous operation at SG up to 1.7.
Yes. The CSW Series is specifically designed for STP applications including inlet pump sumps, inter-stage lift pumps, and sludge return circuits within the STP. For inlet duty (raw, unscreened influent), the dual TC-vs-TC mechanical seal provides the extended service life needed for continuous-duty operation in grit-laden influent. For inter-stage lifting of settled or activated sludge (SG 1.1–1.3), the CSW’s variable HP range and wide flow-head envelope cover the full STP duty spectrum from small rural STPs (1–5 MLD) to large urban STPs (50–200 MLD) when multiple units are deployed in parallel.
The CSW Series handles soft fibrous material — natural fabric, paper, food fibre, light cotton rags — that forms part of normal municipal sewage. For applications dominated by synthetic fibrous waste (wet wipes, polypropylene fibres, industrial yarn, heavy textile), the CNC Non-Clog Series with its vortex (non-contact) impeller is the preferred choice. The vortex impeller never contacts fibrous solids, eliminating the wrapping mode of failure that affects any impeller with blade clearances below 100 mm. For mixed duty — fibrous sewage at higher flows and heads beyond the CNC range — the CSW with regular inspection intervals is the practical choice.
The CSW Sewage Series is part of a complete submersible pump portfolio covering clean dewatering, non-clog sewage bypass, and heavy abrasive slurry duties:
2,500+ customers served across 5,000+ completed projects and installations worldwide. ISO 9001:2015 · CE · ZED Gold · NSIC · UL Compliance · EAC — 6 certifications across the full product range.