How to choose a pump for dirty water: flow rate and head

For dirty water, the choice starts from four figures: how much water you need to move (flow rate), how high you need to send it (head), how large the biggest solid reaching the pump is (solids passage) and whether you have mains power. In the collection, flow rates range from about 2,000 l/h up to 5,000 l/min (300 m³/h) and heads from 6 to 38 m. If you work in a trench or a tank, start with a submersible pump for dirty water; if you have no power or need to cover large volumes, consider an engine-driven pump.

The types

• Submersible electric pump: it is lowered to the lowest point and works immersed. For solids-laden water there are the Wortex DXG 1000/1200 (solids passage 35 mm) and the Wortex PROFI-T (30 mm, vortex impeller). For smaller jobs, the Makita PF0610 and PF1110 and the Annovi Reverberi ARUP 1100XD have a solids passage of 35 mm.
• Pedrollo electric pumps: series such as BC4, VX4 and MC4 for medium and high flow rates. The Pedrollo BC4 reaches 1,200 l/min, the Pedrollo VX4 900 l/min and the Pedrollo MC4 2,900 l/min.
• Battery pump: Milwaukee dark-water pumps, such as the M18 Hydropass (5,670 l/h, maximum height 5.1 m), are for places without a socket and for quick jobs.
• Engine-driven pump: with a petrol engine, for sites without power and for large flow rates. There are the Genmac Semitrash and Genmac Trash, the Pramac MP36-2 and MP56-3 and the Wortex LW 80-IS Trash. The Breaker PA 2" has a separate pump and power unit, with a 6 m hose: 950 l/min and a maximum head of 20 m.
• Hydraulic or pneumatic pump: the Breaker PI W2 and Breaker PI W3 are submersible and run on pressurised oil, from a hydraulic power unit or a machine such as an excavator. The PP1 runs on compressed air and uses 2,820 l/min at 6 bar. They are useful where a hydraulic system or a compressor is already on site.
• Emergency kit: such as the Pedrollo Plug & Drain emergency drainage kit, for sudden flooding.

How to choose according to the job

Situation	What to get	Why
Flooded construction trench	Submersible pump for solids-laden water, solids passage from 30-35 mm upwards	Handles water with mud and sand; the exact millimetres are on the data sheet.
Site without power	Petrol engine-driven pump	It does not depend on the grid and moves large volumes; for mud and slurry there is the Trash.
Flooded cellar or room	Medium-flow submersible pump with float switch, or an emergency kit	It empties from the lowest point: check the minimum suction level.
Manholes and tanks	Submersible pump with handle	Lowered on a rope and easy to recover.
Quick job away from base	Battery pump	No cable to run out.
Site with an excavator or a compressor	Breaker hydraulic or pneumatic pump	Uses the pressurised oil or compressed air you already have.

Solids passage: how many millimetres you need

Solids passage is the diameter of the largest solid body the pump lets through. It is the figure that decides whether the pump clogs. These are the values given on the data sheets in the collection.

Pump	Solids passage	Other data-sheet figures
Makita PF0610 / PF1110	35 mm	180 and 250 l/min, maximum immersion 5 m
Annovi Reverberi ARUP 1100XD	35 mm	16,500 l/h, head 10.5 m, maximum immersion 7 m
Wortex DXG 1000/1200	35 mm	maximum immersion 5 m, liquid up to 35 °C, continuous duty
Wortex PROFI-T	30 mm	recessed vortex impeller, maximum immersion 20 m, liquid up to 35 °C
Pedrollo BC4	50 mm	up to 1,200 l/min, head up to 6 m
Pedrollo VX4	50 mm (VX4-10/50), 65 mm (VX4-10/65)	up to 900 l/min, head up to 7 m
Pedrollo MC4	55 mm	up to 2,900 l/min, head up to 16 m
Genmac Semitrash	not in mm: solids allowed up to 30%	3" connection, 1,100 l/min
Genmac Trash	not in mm: solids allowed up to 50%	3" or 4" connection, 1,100 to 1,600 l/min
Wortex LW 80-IS Trash	not stated	750 l/min, maximum head 30 m, maximum suction height 7 m, 39 kg
Pramac MP56-3	not stated	930 l/min, total head 26 m, maximum suction height 8 m

For fine mud and sand, models with 30-35 mm are enough. If leaves, small stones or larger fragments end up in the trench or sump, move to models of 50 mm and above. Do not pick a pump whose solids passage is barely equal to the biggest piece you expect to find: leave some margin.

For engine-driven pumps the figure in millimetres is often missing. Genmac gives the solids allowed as a percentage: up to 30% for the Semitrash (flooding, livestock drainage, sandy or slightly muddy water) and up to 50% for the Trash (building sites, emergency road repairs, mud and slurry). A percentage is not a diameter: if you have to pump water with large debris, ask the AMES technicians for the maximum diameter that passes.

Vortex impeller or open impeller: what changes

Solids passage also depends on the impeller, the part that sets the water in motion. These are the two families you will meet most often.

• Vortex impeller (recessed): it sits set back in the pump body and sets the water rotating, without the solids passing through the vanes. It copes better with fibres, leaves and debris, but it usually delivers less for the same power. The Wortex PROFI-T is described on its data sheet with a recessed Vortex impeller (solids passage 30 mm); the Breaker hydraulic pumps PI W2 (840 l/min) and PI W3 (1,920 l/min) have a vortex impeller and are indicated for dirty water with solids.
• Open, semi-open or channel impeller: the vanes are exposed and the water passes through them together with the solids. It usually moves more water for the same power and copes well with mud and sand, but a long or fibrous body can get caught between the vanes.

On the data sheet look for the impeller entry: the type is not always given, the material often is (AISI 304 stainless steel on the DXG 1000/1200, cast iron on PROFI-T, BC4, VX4 and MC4). The impeller type does not replace the figure in millimetres: always read that too.

The features to check

Flow rate. On the data sheets it is given in l/min, l/h or m³/h (400 l/min equal 24 m³/h). In the collection it goes from about 2,000 l/h up to 5,000 l/min.

Head. It is the maximum height the pump can reach, from 6 m to 38 m in the data. The higher it is, the lower the flow at that height: check the data sheet for real use.

Motor. Electric with 2 or 4 poles, petrol for engine-driven pumps, or pressurised oil or compressed air for the Breaker pumps.

Materials. Pump body in cast iron, technopolymer or AISI 304/316 stainless steel; impeller in stainless steel, cast iron, Noryl or technopolymer. Stainless steel is the choice for the most aggressive water; ask the technicians if you do not know what liquid you have.

Protection and temperature. The Wortex DXG and PROFI-T and the Pedrollo pumps are rated IP68; the ARUP 1100XD is IPX8. The maximum liquid temperature is 35 °C for the Wortex DXG and PROFI-T and for the ARUP, and 40 °C for the Pedrollo BC4, VX4 and MC4.

Weight. From the 3.8 kg of the Kärcher SP 9500 Dirt to the 39 kg of the Wortex LW 80-IS Trash engine-driven pump: if you move it by hand often, weight matters.

How much water the pump needs around it

Three figures appear on the data sheets that are easy to confuse.

• Minimum suction level: the water height below which the pump no longer draws. It is the figure to check if you want to leave the floor dry: 65 mm for the DXG 1000/1200, 100 mm for the PROFI-T, 50 mm for the Makita PF0610 and PF1110, 45 mm of residual level for the ARUP 1100XD. The Breaker PP1 pneumatic pump gives a minimum water depth of 22 mm.
• Minimum immersion for continuous duty: given for the Pedrollo pumps, 500 mm for BC4 and VX4 and 550 mm for MC4. With less water, continuous duty is not guaranteed.
• Maximum immersion: the depth to which you can lower the pump. 5 m for the DXG 1000/1200 and the Makita pumps, 7 m for the ARUP 1100XD, 20 m for the PROFI-T, up to 10 m for the Pedrollo BC4, VX4 and MC4 with a power cable of suitable length.

When you need a float switch

A float switch is needed when the pump has to start and stop by itself with the water level: a collection sump, a cellar where water keeps rising, a tank that fills up. If instead you are emptying a trench and watch the pump while it works, the switch on the pump is enough.

The data sheets say how the control is built. The Kärcher SP 9.500 Dirt has an adjustable float and switches from automatic to manual operation; the Kärcher SP 22.000 Dirt Level Sensor has a level sensor that sets the suction level. On the Wortex pumps the float only appears in the instructions for use: check that it moves freely.

Set the float so that the pump stops before the level drops below the minimum suction level, and keep it clear of walls and cables: if it gets stuck, the pump does not stop and runs dry. The data sheets of engine-driven, hydraulic and pneumatic pumps do not list a float: here you watch the level yourself.

For submersible pumps for solids-laden water there is a dedicated collection, Submersible Pumps for Solids-Laden Water. If the water is clear or only slightly cloudy and you mainly need to empty, read the guide to submersible drainage pumps, which also covers float-switch control.

Common mistakes

• Hanging the pump by its cable. It is lowered on a rope tied to the handle, never by the power cable.
• Resting it on soft mud. It must sit on a solid bottom, otherwise it draws in debris.
• Choosing only on flow and head. With solids-laden water the solids passage comes first: on the data sheets that give it, it ranges from 30 to 65 mm.
• Running the pump dry. It is damaged in a short time: always check that it is drawing water and that the float moves freely.
• Forgetting to prime the engine-driven pump. The pump body is filled with water before starting.
• Not rinsing it after the job. A short run in clean water stops mud and sand from hardening inside; after use in dirty water, also check the impeller.
• Mixing up minimum suction level and minimum immersion. They are two different values: the first says how far down the pump empties, the second how much water is needed for continuous duty.

Frequently asked questions

Submersible or engine-driven pump: which one?

The submersible is handy in trenches, sumps and tanks. The engine-driven pump is for when there is no power or large volumes are needed.

What does head mean?

It is the height to which the pump can push the water. If you have to take it higher than the stated value, it will not come out.

Can it handle water with sand?

It depends on the pump. Check that it is indicated for solids-laden or dark water and look at the solids passage on the data sheet; the Genmac Semitrash, for example, is indicated for sandy or slightly muddy water. If in doubt, ask the AMES technicians.

How many millimetres of solids passage do I need?

It depends on what reaches the pump: for fine mud and sand, 30-35 mm is enough; with leaves, small stones or larger debris you need 50 mm or more. On the data sheets that give it, the values range from 30 to 65 mm.

What does “solids allowed up to 50%” mean?

It is a percentage, not a diameter: it says how much of it can be solid, not how large a piece can be. For the maximum diameter, ask the AMES technicians.

What does IP68 mean?

It is the protection rating given for the submersible pumps in the collection: it means the pump is built to work immersed. The ARUP 1100XD states IPX8.

All the pumps are in the Pumps and engine-driven pumps for dirty or waste water collection: to choose the model or request a quote, contact the AMES technicians.