Water pumps are sold by port size and horsepower, but neither tells you whether a pump will do your job. What matters is the kind of water you are moving, how far and how high it has to go, and how fast. Answer those three questions and the right class of pump is usually obvious.
Quick answer
For clean water, such as draining a pool, filling a tank or moving water from a creek, a 2-inch engine-driven transfer pump or an electric submersible utility pump is the usual choice. For muddy or debris-filled water, choose a semi-trash or trash pump. For sprinklers, firefighting or pushing water a long way uphill, choose a high-pressure pump. Size on the flow and total head you need, not on horsepower.
In this guide
The main types
| Type | Handles | Flow and pressure | Typical use |
|---|---|---|---|
| Transfer (clear water) | Clean or lightly dirty water, no solids | High flow, moderate pressure | Draining, filling tanks, moving water from ponds and creeks |
| Semi-trash | Sandy or muddy water with small solids | High flow, lower pressure | Dewatering, flooded areas with silt |
| Trash | Dirty water with leaves, twigs and gravel | Very high flow, low pressure | Construction dewatering, flood water, ponds |
| Diaphragm (mud pump) | Thick sludge, water with high solids content, can run dry | Low flow, low pressure | Septic, slurry, pits that fill slowly |
| High-pressure | Clean water | Lower flow, high pressure | Irrigation sprinklers, firefighting, long uphill runs |
| Submersible utility (electric) | Clean to lightly dirty water | Moderate flow, low to moderate head | Flooded basements, pools, hot tubs, tanks |
Which class for which job
Transfer pump, 2 inch
Best for: Draining pools and tanks, filling stock tanks, moving water from a creek or pond
- Flow
- Up to roughly 150 to 200 gallons per minute at low head
- Total head
- Typically 90 to 130 feet
- Solids
- Essentially none
- Engine
- Small gasoline engine, about 3 to 5 HP class
What we like
- Highest flow for the price
- Light enough to carry
- Simple to set up and prime
What to consider
- Impeller and seal wear quickly in sandy or muddy water
- Not for solids of any size
Our take: The all-round choice for clean water on a property.
Semi-trash pump, 2 to 3 inch
Best for: Dewatering muddy ditches and flooded areas where small debris is present
- Flow
- Roughly 150 to 300 gallons per minute depending on size
- Solids
- Small, typically up to about 5/8 inch
- Design
- Cast-iron or hardened impeller, wider passages
What we like
- Tolerates silt and sand that would wear out a transfer pump
- Still good flow and pressure
What to consider
- Not for leaves, twigs or gravel
- Heavier than a transfer pump
Our take: The sensible step up when the water is not clean.
Trash pump, 2 to 4 inch
Best for: Construction dewatering, flooded excavations, ponds with vegetation
- Flow
- Roughly 185 to 700 gallons per minute depending on size
- Solids
- Up to about 3/4 inch (2 in), 1 to 1.5 inch (3 in), 2 inch (4 in)
- Design
- Open impeller, clean-out port on the volute
What we like
- Passes solids that would jam anything else
- Moves large volumes quickly
- Clean-out port clears blockages without disassembly
What to consider
- Lower pressure than a clear-water pump of the same size
- Heavy; 3-inch and larger need wheels or two people
Our take: If the water has anything in it, start here.
High-pressure pump
Best for: Running sprinklers, firefighting lines, pushing water uphill or over long distances
- Flow
- Lower, often 50 to 120 gallons per minute
- Total head
- 200 to 300 feet or more
- Outlets
- Often multiple smaller discharge ports
What we like
- Pressure to run several sprinklers or a fire hose
- Lifts water over hills and long runs
What to consider
- Low flow compared with a transfer pump
- Clean water only
Our take: For irrigation and fire protection, nothing else will do.
Submersible utility pump (electric)
Best for: Flooded basements, draining pools and hot tubs, emptying tanks where power is available
- Flow
- Typically 20 to 80 gallons per minute
- Head
- Usually 20 to 30 feet
- Power
- 120 V, usually 1/4 to 1/2 HP
What we like
- No priming; drop it in and plug it in
- Quiet, no exhaust, usable indoors
- Pumps down to a fraction of an inch on some models
What to consider
- Needs electricity, which may be out during a flood
- Limited head and flow
Our take: The right tool whenever there is a power outlet and clean water.
The specifications that matter
Flow
Gallons per minute (GPM) or gallons per hour. Manufacturers quote the maximum at zero head. Real flow falls as the pump works against height and hose friction. A 2-inch pump that moves 150 GPM on paper might deliver 90 GPM through 100 feet of hose and a 20-foot rise. Our explainer on pump head and flow shows how to read a pump curve.
Total head
The total height a pump can push water, counting suction lift plus discharge rise plus friction loss. The maximum head figure is the point where flow drops to zero. Choose a pump whose curve gives you the flow you need at your total head, with a margin.
Suction lift
How far below the pump the water surface can be. Atmospheric pressure limits any surface pump to a theoretical 33 feet at sea level, and about 25 feet is the practical ceiling. Pumps work best with a short suction lift; put the pump close to the water and let the discharge do the long run.
Solids handling
The largest particle the pump can pass without jamming, given in inches. Trash pumps are defined by this figure.
Port size
Larger ports mean higher flow. Never run a pump with a smaller suction hose than its port size; it starves the impeller and causes cavitation.
Hoses and fittings
- Suction hose must be rigid or wire-reinforced so it does not collapse under vacuum. Lay-flat hose is for discharge only.
- Strainer on the suction end, sized for the pump’s solids rating, kept off the bottom of the pond.
- Discharge hose can be lay-flat; longer and narrower hoses cost flow.
- Camlock fittings make connecting and disconnecting quick and leak-free.
Engine-driven or electric?
Engine-driven pumps work anywhere and move far more water, but they must be run outdoors, need fuel and maintenance, and are loud. Electric pumps are quiet, can run indoors and start instantly, but depend on power that may be out in exactly the emergency you bought them for. Many households keep a submersible utility pump for everyday jobs and a small engine-driven pump for floods and outages.
Frequently asked questions
What size water pump do I need to drain a pool?
A 2-inch transfer pump or a submersible utility pump in the 40 to 80 gallons per minute range will empty a typical residential pool in a few hours. Check local rules on where pool water may be discharged.
What is the difference between a trash pump and a regular water pump?
A trash pump has an open impeller and wide internal passages that let solids pass through, plus a clean-out port. A regular transfer pump has tight clearances for better pressure and will jam or wear out quickly on debris. Our comparison of trash and transfer pumps goes into detail.
How far can a pump push water?
It depends on the pump's head rating and the hose. A typical 2-inch transfer pump rated at 100 feet of head can push water up a 40-foot rise through a few hundred feet of hose while still delivering useful flow. High-pressure pumps go much further and higher.
