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An engine-driven pump is a pump powered by a combustion engine: it works where there is no mains electricity (building sites, fields, ponds, flooded cellars). To choose well, you need to balance the fuel, the flow rate, the head to overcome and the type of water to be pumped.
Petrol or diesel: which engine to choose?
The choice of fuel mainly depends on how often you use the pump and on the flow rate you need. Here are the general trends, to be confirmed on the product page of each model:
| Criterion | Petrol | Diesel |
|---|---|---|
| Typical use | Occasional use, emergency pumping, small to medium flow rates | Frequent or prolonged use, high flow rates |
| Weight and size | Generally lighter and more compact | Generally heavier and bulkier |
| Purchase price | Generally more affordable | Generally higher |
| Starting | Most often with a recoil starter | Recoil or electric starter depending on the model |
| Fuel | Keeps less well: drain it before long storage | Keep it clean (avoid water and impurities in the tank) |
Some small petrol engines run on an oil and petrol mixture: always check the manual before the first fill-up.
Clear, loaded or heavily loaded water
An engine-driven pump is not designed for every liquid. Start by identifying the water to be pumped:
- Clear water (ponds, tanks, watering, emptying a clean excavation): a clear water engine-driven pump is generally enough.
- Loaded water (mud, sand, leaves, building sites): choose a loaded water engine-driven pump, whose solids-handling capacity is given on the product page.
- Sea water and chemical liquids: a specific model is required, see the engine-driven pumps for sea water and chemical liquids.
Pumping loaded water with a pump designed for clear water wears the impeller and the seal very quickly. Also consider a strainer to hold back large debris, and find accessories in the engine-driven pump accessories category.
Flow rate, head and suction: what to calculate
The flow rate is given in m³/h (1 m³/h is about 16.7 l/min). The total dynamic head (TDH) is the geometric height to overcome, plus the friction losses in the hoses (and the residual pressure you want at the end of the line). The calculation is explained in the page Calculating the total dynamic head. Reminder: 1 bar is about 10 metres of water column (mWC).
On the suction side, a surface pump cannot “pull” water beyond about 10 m in theory. In practice, count on 6 to 8 m at most (friction losses, water temperature, altitude). The lower the water, the lower the real flow rate: place the pump as close as possible to the water level.
Worked example
Emptying a pond with 3 m of suction lift, a discharge point 5 m above the pump and 60 m of hose with friction losses estimated at 4 m: TDH ≈ 3 + 5 + 4 = 12 m, or about 1.2 bar. You then need a pump that delivers the flow you want at 12 m of head on its curve. The mistake to avoid: choosing on the maximum advertised flow rate, which corresponds to a head close to zero.
Priming, maintenance and safety
- Priming: before starting, the pump casing must be filled with water. A foot valve with strainer at the end of the suction hose keeps the water column from draining.
- Suction tightness: an air leak on a coupling or a seal prevents priming. Use a suitable suction kit and couplings in good condition.
- Dry running: never run the pump without water, the mechanical seal overheats and gets damaged.
- Maintenance: engine oil level, air filter, spark plug or fuel filter depending on the engine, and draining the fuel before long storage. Follow the schedule in the manual.
- Safety: never run a combustion engine in an enclosed space (exhaust gases), and refuel with the engine stopped and cooled down.
In short, here is the selection method in 5 steps:
- Identify the water: clear, loaded, heavily loaded, or a specific liquid.
- Measure the heights: suction (6 to 8 m at most in practice) and discharge.
- Calculate the TDH by adding the friction losses linked to the length and diameter of the hoses.
- Choose the flow rate by reading the model’s curve at the calculated head, then the fuel according to how often you will use it.
- Complete the setup: hoses, strainer, valve, and couplings compatible with your hoses and with those of the pump.
Frequently asked questions
Petrol or diesel for occasional use?
For one-off use or emergency pumping, a petrol engine, generally lighter and more affordable, is often enough. Diesel is more suitable for frequent, prolonged or high-flow use. Always check the specifications on the product page.
Why won’t my engine-driven pump prime?
The most common causes are a casing not properly filled with water, an air leak on the suction side, a stuck foot valve or an excessive suction lift. Check these points before suspecting the pump itself.
Which hose diameter should I use?
Generally at least the diameter of the pump’s suction port, or larger if the line is long: a hose that is too narrow or too long increases friction losses and reduces the flow rate. The guide choosing a hose or a pipe explains the method.
Going further
Engine-driven pumpsAll the petrol and diesel models in the shop.Loaded water engine-driven pumpsFor muddy, sandy or building-site water.Suction kitsHoses, strainers and couplings ready to fit.Choosing a hose or a pipeDiameter, working pressure and type of liquid.Choosing a fire-fighting engine-driven pumpFlow rate, pressure and couplings for fire protection.