TBZ31.5 Drainage Pump Description
When a small pit, sump, or pond starts filling faster than you'd like, you don't need an oversized industrial unit sitting in the water — you need a compact, reliable pump that goes straight in, starts on demand, and keeps moving dirty water without clogging. The Hydroman TBZ31.5 is a 1.5 kW (roughly 2 HP) submersible drainage pump built for exactly that job: dirty water, drainage water, and general sewage-type flow in sumps, pits, ponds, and light-duty drainage systems.
If you've been comparing a 1.5 HP submersible drainage pump against something rated "over 1 HP" and wondering what the practical difference actually is, the TBZ31.5 sits right in that in-between class — enough power to move real volume out of a sump or pond, small enough to handle by hand and drop straight into a pit without a crane or a hoist.
What the TBZ31.5 Is Built to Do
The TBZ31.5 is an electric submersible drainage pump with a submersible centrifugal, non-clog hydraulic design. You lower it directly into the sump, pit, tank, or pond — there's no dry-pit installation, no suction line to prime, and no separate pump house to build. The impeller and volute are shaped with clearances generous enough that water carrying rags, light debris, and moderate suspended solids passes through without packing up around the vanes, which is the failure mode that kills ordinary sump pumps in dirty-water service.
You'll find this pump doing its job in a few recurring situations:
One thing worth being direct about: the TBZ31.5 does not have a bottom agitator. That's a deliberate design choice, not an oversight, and it matters for how you use this pump. Without an agitator, it's built for water-based dirty water, sewage, and effluent — liquids where solids are already suspended, floating, or entrained in the flow. It is not the right choice for settled sludge, sand beds, or slurry that needs to be mechanically stirred up off the pit floor before it will move. If your job involves sand, silt that settles out, or thick sediment sitting on the bottom, you want a pump from Hydroman's agitator-equipped slurry or sand pump range instead. If your water is dirty but not settling — stormwater, sewage, effluent, general drainage and pond water — the TBZ31.5 is squarely in its element.
Hydroman® TBZ31.5 Submersible Drainage Pump Curve
TBZ31.5 at a Glance
| Model | Outlet | Motor power | Rated current (400V) | Rated capacity | Rated head | Max capacity | Max head | Impeller Passage | |||
| (50Hz) | mm | kW | HP | A | m³/h | m³/min | m | m³/h | m³/min | m | mm |
| TBZ31.5 | 80 | 1.5 | 2 | 3.5 | 30 | 0.5 | 8 | 40 | 0.67 | 14.5 | 8.5 |
A quick, honest note on that table: exact flow and head depend on the specific impeller fitted to your order, so the ranges above describe where a 1.5 kW frame typically lands rather than a single fixed curve. Send us your required flow, head, and liquid characteristics and we'll confirm the exact performance curve, discharge diameter, maximum solids passage, voltage, and weight for your unit before you order — that's a more useful number than a generic spec sheet anyway.
How a Submersible Drainage Pump Like This Actually Works
You lower the TBZ31.5 into the sump, pit, or pond so the pump body is fully submerged. When the motor starts, the impeller spins and generates centrifugal force at the eye of the impeller. Liquid is drawn in through the suction inlet at the base of the pump, the impeller adds velocity to it, and the volute casing converts that velocity into pressure as the flow moves outward and up toward the discharge. From there it's pushed through your discharge pipe or hose to wherever you're routing the water — a drain, a holding tank, a ditch, or simply away from the area you're clearing.
The mechanical seal between the motor housing and the wet end is what keeps the pumped liquid out of the motor compartment while the unit runs fully submerged, and it's one of the components worth checking periodically, since seal wear is the most common root cause of a submersible pump failing early in dirty-water service.
Where It Gets Used
Sump and pit drainage. As a sump submersible drainage pump, the TBZ31.5 handles residential, light commercial, and small industrial pits that need automatic or manual dewatering.
Pond and small reservoir transfer. As a pond pump, it can draw down or transfer water from ponds and small reservoirs where the liquid stays within its rated solids range.
Construction and landscaping. Shallow excavations, trenches, and small foundation pits fill with rainwater and groundwater, and this class of electric submersible drainage pump clears them without a permanent installation.
Light sewage and effluent duty. As a submersible sewage drainage pump for smaller volumes, it's suited to effluent transfer and general dirty-water handling where the liquid contains typical wastewater solids rather than dense grit.
Flood response and emergency dewatering. For a flooded basement or a low spot that fills after heavy rain, this is a pump you can carry in, drop in, and switch on with no priming step.
Choosing Between a 1.5 HP Sump Pump and a 1.5 kW Drainage Pump
It helps to think in terms of duty, not just the model name. A 1.5 kW class pump like the TBZ31.5 is right-sized for a household or light commercial sump, a small pond, or a modest pit where you're moving a manageable volume a short vertical distance — this is the "over 1 HP" bracket rather than the smallest fractional-horsepower sump pumps, so it has real reserve capacity for a busier pit or a slightly deeper lift. If your job is a large construction dewatering site, a plant sump feeding a treatment system, or a lift station running continuously across multiple shifts, you'd want to step up into Hydroman's larger-frame drainage pumps instead — ask us and we'll point you to the right size.
A few numbers to work with when you're sizing:
The Hydraulic Institute, the ANSI-accredited standards body for the pump industry in North America, publishes ANSI/HI 11.6, the acceptance-test standard written specifically for rotodynamic submersible pumps. It lays out uniform procedures for performance testing, hydrostatic pressure testing, required suction head verification, submersible motor integrity checks, and vibration testing of submersible solids-handling pumps, giving purchasers, specifying engineers, and manufacturers a shared, independent basis for confirming that a pump performs the way its datasheet claims. It is a useful independent reference point if you want to understand what verified performance should mean when you are evaluating any submersible drainage pump for sale, not just Hydroman's.
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Item No. | Part name | Material | Item No. | Part name | Material | |
| 01 | Hose coupling | Cast iron | 28 | Rotor | Shaft: AISI420SS | ||
| 02 | Handle | Rubber & steel | 31a | Bearing | Ball bearing | ||
| 05 | Upper cover | Cast iron | 31b | Bearing | Ball bearing | ||
| 11 | Motor body | Cast iron | 33 | Motor protector | — | ||
| 13 | Pump body | Cast iron | 34 | Mechanical seal | Sic-Sic/Carbon-Sic (≤2.2kW) Sic-Sic/Sic-Sic (≥3.7kW) |
||
| 14 | Impeller | High chrome alloy | 35 | Oil seal | — | ||
| 16 | Inlet plate | Ductile iron | 47 | Cable | — | ||
| 25 | Strainer | Steel | |||||
| 27 | Stator | — |
 |
|
| Model (50/60Hz) | TBZ31.5 |
| d (mm) | 80 |
| A (mm) | 235 |
| A1 (mm) | 173 |
| B (mm) | 535 |
| D (mm) | 216 |
| H (mm) | 505 |
| W1 (mm) | 120 |
| N.W (Kg) | 36 |
| G.W (Kg) | 40 |
| Packing dimension(mm) | 610x265x265 |
Getting a submersible drainage sump pump running correctly the first time comes down to a short list of things done in order: inspect the unit on arrival, confirm the model matches your duty point rather than assuming it does, set the pump on stable, level footing in the pit or pond bed, connect the discharge hose or pipe securely, check the power cable routing and your electrical protection (ideally a ground-fault/RCD device given it's a wet application), and confirm the pump is adequately submerged before you switch it on. Once it's running, watch flow, current draw, and noise for the first few minutes — if anything looks off, stop it rather than letting a small problem run for hours.
A few habits that extend service life: keep the intake clear of large debris that could still exceed the pump's rated solids passage, don't run it dry or outside the head-and-flow window it was selected for, and avoid sharp bends or crushing loads on the power cable during handling.
Routine inspection covers the casing, impeller, suction inlet, discharge connection, power cable, mechanical seal, and fasteners — most of this can be done visually during a scheduled pull for cleaning. If the pump won't start, check the power supply first, then the electrical protection trip, the cable, and finally the motor. Low flow or head is most often a blocked intake, a restricted or undersized discharge line, or impeller wear rather than a motor problem. If the motor is overheating, check submergence depth first — running with insufficient liquid coverage is the most common cause in the field, followed by electrical faults or a blocked hydraulic passage.
Before putting the pump into long-term storage, clean it thoroughly, inspect the wear components, and protect exposed metal surfaces per the storage guidance in your manual.
You're not just buying a casting and a motor — you're buying pump selection support from a manufacturer that will ask about your flow, head, and liquid characteristics before recommending a unit, rather than pointing you at whatever's in stock. Hydroman builds the TBZ31.5 for genuine dirty-water and drainage duty rather than treating it as a clean-water pump with a different label, backs it with OEM and customized configurations where your project needs something outside the standard catalog, and provides ongoing spare parts and technical support after the sale — which matters more than the purchase price once the pump has been in service for a year or two. If you're weighing submersible drainage pump price against a cheaper alternative, ask what's actually backing it up when a seal wears out down the line.
What is a submersible drainage pump? It's an electrically driven pump designed to run fully submerged inside a sump, pit, pond, or excavation, drawing in water through a bottom inlet and discharging it through a connected pipe or hose — no external suction line or priming needed.
What is the Hydroman TBZ31.5 used for? Drainage of dirty water, sewage, and effluent in sumps, pits, ponds, and small construction or drainage jobs — anywhere you need to move water that isn't clean but also isn't heavy settled sludge or sand.
Does the TBZ31.5 have a bottom agitator? No. It's built for dirty water, sewage, and effluent where solids are already suspended or floating in the liquid. For applications involving settled sludge, sand, or slurry that needs to be stirred up off the pit floor, ask about Hydroman's agitator-equipped slurry and sand pump ranges instead.
Is the TBZ31.5 an electric submersible drainage pump? Yes — it's driven by a 1.5 kW electric motor rated for submerged operation.
What's the difference between a drainage pump and a sewage pump? In practice the terms overlap a lot. Drainage pumps are generally sized around water removal and dirty-water flow, while sewage pumps are configured with impeller clearances and solids passage suited to wastewater specifically. The right choice comes down to your liquid's actual solids content and size, not the label on the pump.
How do I pick the best submersible drainage pump for my site? Start from required flow and head, then check liquid characteristics and maximum solids size, match the discharge pipe or hose size, and confirm your power supply. Send those numbers to a pump engineer rather than sizing off a catalog photo.
Can this pump be used as a sump pump? Yes — it's well suited to household, light commercial, and small industrial sump pits, as well as pond and small reservoir drainage.
Where can I get a price for the TBZ31.5? Send Hydroman your required flow, head, liquid characteristics, power supply, and quantity, and you'll get a project-specific quote rather than a generic list price.
Request a Quote for the Hydroman TBZ31.5
Need a compact, dependable submersible drainage pump for a sump, pit, or pond? The Hydroman TBZ31.5 is a 1.5 kW electric pump built for dirty water, sewage, and effluent drainage where reliability and easy handling matter more than anything else on the spec sheet.
Send us the details below and we'll come back with the right configuration and a submersible drainage pump price for your project, not a generic list price:
Required flow · Required head · Liquid type (dirty water, sewage, effluent, general drainage) · Solids content and maximum particle size · Voltage and frequency · Quantity · Application · Destination country
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