Dirty Water Motor Pumps

Dirty water (semi-slurry) motor pump — what it is and when to choose one

A dirty water (semi-slurry) motor pump is a petrol-driven centrifugal pump with semi-open impeller, designed to deliver water containing solids up to 8-9 mm diameter — sand, small stones, leaves, mud, silt. Between clean water pump (up to 5 mm) and sludge pump (up to 27 mm) — covers typical construction and municipal work needs. Choose it when the pumped medium is not clear (groundwater, flood water, pond water, foundation pit water), but also not thick sludge. Flow 500-900 l/min (30-54 m³/h), maximum head 26-29 m.

Models table — dirty water motor pumps Koshin

Cheapest: STV50X (Koshin K180, from ~1,780 PLN net) — for typical home and plot work. Highest flow: STV80X and STH80X (900 l/min, 3") — for dewatering large excavations and basements. Highest head: STH50X (29 m, Honda GX120) — when you need to pump to a higher floor.

STV (Koshin K180) vs STH (Honda GX) — which engine to choose

STV series have Koshin K180 engine (Japanese, dedicated to this brand) — 20-30% cheaper, equally durable (3,000-5,000 engine hours with regular service). STH series have Honda GX engine (GX120 in STH50X, GX160 in STH80X) — more expensive but with better service parts availability in Poland and better resale value on secondary market. Hydraulic performance of both series is comparable (small plus for STH50X with 29 m head vs STV50X 26 m). Choice: STV for personal use, STH for rental companies or planned intensive use.

Frequently asked questions — dirty water motor pumps

Which motor pump for dewatering a construction excavation?

For typical foundation excavation (depth 1.5-3 m, groundwater with sand and mud) choose Koshin STV50X (2") or STH50X (Honda GX120, 2") — flow 580-600 l/min, handling solids up to 8 mm. Excavation 4×3×1 m = 12 m³ → STV50X empties in ~22 minutes. For deeper excavations (>3 m) or larger volumes (flooded pit 50+ m³) — 3" model STV80X/STH80X (900 l/min, pumps 27 m³ in half an hour). For very muddy terrain with large particles (>9 mm) — choose sludge pump KTH50X.

Will a semi-slurry motor pump drain a flooded basement?

Yes — this is one of the main uses. Basement 50 m² flooded with water to 30 cm depth = 15 m³ (15,000 l) of water. STV80X or STH80X (3", 900 l/min) will empty it in ~17 minutes (at zero head) or ~25-30 minutes in real conditions (4 m head + 7 m suction hose). Necessary equipment: suction hose with strainer basket (390 PLN net for 3"/75 mm × 8 m), discharge hose to drain water outside (320 PLN net for 3"/20 m). Pump will suck water from depth up to 8 m, but for effective work leave 1-1.5 m buffer.

How does a dirty water motor pump differ from a submersible pump?

A dirty water motor pump is a surface-mounted centrifugal pump with gasoline engine — stands outside the excavation/basement and draws water through suction hose. Advantages: independence from power (works in field and during power failure), mobility (29-31 kg). A submersible pump (electric) is immersed directly in water — requires power connection and waterproof installation. Choice depends on conditions: motor pump for field work without power, submersible for permanent work in basement with socket. Norwit offers both: motor pumps in this category and electric submersible pumps in /en/c/electric-pumps.

Can I pump water with fine sand and small stones?

Yes — dirty water motor pumps (STV50X, STV80X, STH50X, STH80X) have semi-open impeller designed for this type of medium. They pump water with sand, small stones up to 8-9 mm, mud and silt. Particles larger than 9 mm (gravel over 1 cm, twigs, fine pavement stones) will catch in the impeller and the pump will clog — then use sludge pump handling up to 27 mm. Fine fibers (e.g. fabrics, long leaves) may also catch on the impeller — use strainer basket with dense mesh at hose inlet.

What is the price of a dirty water motor pump?

Semi-slurry motor pump prices depend on engine and diameter: Koshin STV50X (Koshin K180 engine, 2") — from 1,780 PLN net, STV80X (3") — 1,900 PLN net. Honda STH50X (Honda GX120 engine, 2") — 2,800 PLN net, STH80X (Honda GX160, 3") — 3,364 PLN net. Difference between Koshin and Honda is ~1,000 PLN, mainly for premium engine with better parts availability. Additional costs: suction hoses (286-660 PLN) and discharge hoses (215-610 PLN) — usually 800-1,200 PLN for a complete 7-15 m set.

Will a semi-slurry motor pump handle long-term operation (5-10 hours daily)?

Yes — Honda GX and Koshin K180 engines are designed for continuous operation. Practical limitations: 1) fuel tank (2-3.6 l) → refueling every 1.5-3 hours of operation; 2) service kit (filter, oil, spark plug) → replacement every 100 engine hours (every 10-20 days of 5-10 h daily use); 3) engine temperature → for 10+ hour operation ensure pump stands in shade, not in sun. Before a day of intensive work check oil level (pan 0.3-0.6 l) — engine without oil destroys itself in 30 minutes. Full description of Honda and Koshin engine service in generator accessories (same service kits fit).

How long does it take to start a dirty water motor pump?

First start of new motor pump (beginning of season): 2-5 attempts of pulling starter cord after priming pump with water and opening fuel valve. Koshin K180 and Honda GX120/GX160 engines have easy-start system — minimal force to pull. Fully warmed-up pump (after switching off for 5-15 minutes) starts at first pull. After longer storage (>1 month) drain old fuel and pour fresh 95 gasoline — old gasoline oxidizes and creates carburetor deposits making startup difficult. All motor pumps have manual start (cord) — electric starter version not available in this category.