Pumps for plumbing

Pumps for plumbing

By Eamonn Ryan

Matching a pump, and its efficiency, to a specific need is important given that municipalities across Africa grapple with ways of dealing with growing wastewater requirements, it has become increasingly evident that a one-size-fits-all approach does not work in differing conditions, such as sand contents, water quality and existing infrastructure. These play a major role in the specification of future pumping infrastructure requirements. 

There is a clear need for training, KSB Pumps and Valves recently hosted a two-day workshop led by global expert, Ben Harrison, the regional application manager: MEAI KSB Global Corporate Water Department from Germany Halle (Saale), aimed at sharing country specific information and devising ways of working with authorities to provide wastewater solutions.

“Conditions vary from Kenya to DRC, Zambia, South Africa and elsewhere in Africa and we are inviting authorities to work with us to find specific solutions that will work for them.” The aim, he says, is “to bring international standards to local solutions and provide the kind of wastewater solutions that are affordable, durable and appropriate for the kind of maintenance and support that is available in that particular area.

“That means that customers are assured of receiving world-class service wherever they may be, albeit in Johannesburg, Kinshasa, Nairobi or anywhere in Africa. As a customer they can expect the same outcome, the same service and support that they would receive anywhere else in the world. It is also advantageous that sewage pumps are part of the South African production portfolio for quick access to the regional market,” says Harrison.

Why efficiency matters

As a plumber, if you install an inappropriate plumbing pump, the results could be both devastating and costly. Whether you are dealing with flooding issues in the basement, or perhaps you need an industrial pump, there is a right tool for the job.

Pump Saldahna 50

Ian Dickie’s pump on site at Saldanha Bay. Image credit: Ian Dickie

Specifically, septic pumps, sewage pumps and sewage ejector pumps are designed to remove sewage – with solids up to a certain size - from a building where plumbing fixtures and drains are lower than the building sewer line and/or septic tank. Septic pumps must move solids, either by being able to pass large solid objects through the pump without clogging, or by grinding the solids into fine debris. A sewage grinder pump is designed to macerate solid waste so that it can be pumped through a sewer line — perhaps a smaller diameter ‘force main’ sewer line to a public sewer or septic tank.

Sewage grinder/ejector pumps are available in various horsepower models, typically from .5 to 1hp for residential applications, and are sold to operate at various voltages, including 110–120V, 220–240V, 440–480V, and even 600V models using either single-phase (most common) or three-phase motors.

People use terms loosely, specifically the terms sewage pump and septic pump are viewed as synonyms. Indeed, both classes of pumps handle black water or sewage — only the destination differs. A sewage pump, strictly speaking, is pumping black water (toilet waste) to a public sewer line; a septic pump, on the other hand, is pumping black water to a private septic tank and drain-field system.

Therefore, it is important to ask for or to read the manufacturer’s description of what a particular pump model is intended to handle. In addition, even among sewage pumps and grinder pumps that are intended to either pass solids or grind solids up and pump them, the vulnerability of different pump models to damage, clogging, or motor burn-up from debris that people may flush down drains and toilets varies.

Sump pumps are designed to remove unwanted water, such as surface or ground water that leaks into a building. Sump pumps only have to pump water, never solids. A sump pump is normally installed in a pit at the low end of a basement or crawl space floor.

According to Sapsda, the various sectors that a pump system would consist of, are as follows:

  • Pumps
  • Electrical Motors and DrivesSealing Systems
  • Bearings
  • Couplings and Mechanical Drives
  • Control Valves
  • Electrical Cables
  • Switchgear and Control Panels

Be sure to select the proper septic – or sump pump – type.

How to choose an effluent pump

Septic effluent pumps are used to move clarified septic effluent from a pumping chamber to a drain field. They do not have to move solids, but are built to standards of durability more demanding than a typical sump pump used to remove ground water from a building.

Pump manufacturers may claim that the same pump model can serve as a sump pump, effluent pump, and dewatering pump. However, that is not universally the case: while some sump pumps work fine as effluent pumps, others, such as low-cost sump pumps using a vertical float and rod switch and intended for indoor dewatering in basements, may not be suitable for septic effluent pumping.

"It can also be immensely frustrating working on a jobsite after recent rains. The accumulation of wastewater can be caused by rain, flooding, burst or leaking pipes, or simply just groundwater seeping through.”

Be sure to select the proper septic- or sump-pump type. The distinction among sewage pumps or septic pump types is important when installing or repairing a septic system that uses pumps, since choosing the wrong pump can mean a short operating life for the pump, an unreliable septic system, and unnecessary expenses. If you’re replacing an old effluent pump, you can typically use the same horsepower that you had before. That said, you should also pay close attention to the litres per hour rating as they can vary by horsepower. If your pump wasn’t keeping up, you may need to upgrade to a higher horsepower so it can keep up.

If you were able to get several years of service out of your old pump, chances are that it’s the right horsepower to choose. If your previous pump stopped working after a couple of months, you may want to consider a different horsepower. It’s possible that your old pump may have been too weak or too strong for your application.

Types of pumps

  • Velocity pumps: Rotodynamic pumps (or dynamic pumps) are a type of velocity pump in which kinetic energy is added to the fluid by increasing the flow velocity. This increase in energy is converted to a gain in potential energy (pressure) when the velocity is reduced prior to or as the flow exits the pump into the discharge pipe.
  • Positive displacement pumps: The positive displacement principle applies in these pumps:
    • Rotary lobe pump
    • Progressive cavity pump
    • Rotary gear pump
    • Piston pump
    • Diaphragm pump
    • Screw pump
    • Gear pump
    • Hydraulic pump.
  • Impulse pumps: A device for forcing running water to a higher level by using the kinetic energy of flow; the flow of water in the supply pipeline is periodically stopped so that a small portion of water is lifted by the velocity head of a larger portion. Also known as a hydraulic pump.
  • Gravity pumps: A pump deals more with differences in pressure than with gravity itself. At ground level, the pressure is said to be atmospheric pressure (about 10^5 pascals). A pump sucks some air from a pipe, with a piston reducing the pressure inside the pipe (less than the standard atmosphere).
  • Buoyancy pumps: The basic principle of buoyant energy (buoyant hydraulic energy storage system) is based on the well-established technology behind pumped hydro-energy storage plants. The major difference is the arrangement and location of reservoirs at such plants.

Saldahna 2 50

One of the leading pump hire companies in Southern Africa, Ian Dickie, says it prides itself on its ability to adapt, respond and provide tailored solutions to customer pumping requirements, quickly, safely and efficiently. Ian Dickie’s specialist Pump Hire Division offers a full range of both Low and High Head pumps to clients requiring a fast and efficient pump solution anywhere in Southern Africa.

Its range of general purpose and specialist prime assisted centrifugal pumps are available in a variety of forms, with diesel, petrol or hydraulic drive options, ensuring the most effective pump solution for every requirement, in terms of:

  • Comprehensive pump service, from technical advice to full installation
  • Demonstrations of equipment to show the capabilities of its pumps
  • Carrying out site surveys to advise customers on best pumping solutions
  • Offering technical advice
  • Training client staff on how to use and maintain its pumps if required
  • Offering a comprehensive range of accessories and fittings

Water contamination

Alicia Mentz, marketing manager of Agrinet, says: “Wastewater is a common everyday problem that can end up resulting in thousands of rands of water damage especially when the water comes into contact with a material, thereby resulting in destructive processes such as rotting of wood, growth, rusting of steel, de-laminating of materials such as plywood, and many others. It can also be immensely frustrating working on a jobsite after recent rains. The accumulation of wastewater can be caused by rain, flooding,

burst or leaking pipes, or simply just groundwater seeping through.”

There are three basic categories of wastewater, based on the level of contamination.

  • Category 1 Water - Refers to a source of water that does not pose substantial threat to humans and classified as "clean water". Examples are broken water supply lines, tub or sink overflows or appliance malfunctions that involves water supply lines.
  • Category 2 Water - Refers to a source of water that contains a significant degree of chemical, biological or physical contaminants and causes discomfort or sickness when consumed or even exposed to. Known as ‘grey water’. This type carries microorganisms and nutrients of micro-organisms. Examples are toilet bowls with urine (no faeces), sump pump failures, seepage due to hydrostatic failure and water discharge from dishwashers or washing machines.
  • Category 3 Water - Known as ‘black water’ and is grossly unsanitary. This water contains unsanitary agents, harmful bacteria and fungi, causing severe discomfort or sickness. Type 3 category is contaminated water sources that affect the indoor environment. This category includes water sources from sewage, seawater, rising water from rivers or streams, ground surface water or standing water. Category 2 Water or Grey Water that is not promptly removed from the structure and or has remained stagnant may be re classified as Category 3 Water. Toilet back flows that originates from beyond the toilet trap is considered black water contamination regardless of visible content or colour.

“The removal of wastewater is often challenging; in most cases the water needs to be pumped out. Depending on the circumstances, there are two types of pumps that are used for this application, namely; fuel driven pumps and electrical submersible drainage pumps. Both these pump types are generally low pressure, high volume pumps for the purpose of draining water quickly and each having their own advantages and disadvantages,” says Mentz.

Fuel driven pumps

As the name implies, these pumps are driven by either a petrol- or diesel-fuelled engine that in turn rotates the pump shaft, turning the impellor and pumping water. These units are installed above the water line and draw the water with the use of a suction pipe or hose, it is important that the size of the suction pipe is no smaller than 50mm. These pumps are mostly used for Category 1 to Category 2 wastewater but upon request, pumps that pump Category 3 wastewater are available.

Advantages of fuel driven pumps

  • No power or power cables required
  • Easily removeable and stored
  • Economically viable
  • Cost-effective maintenance when using reputable brands like Honda or Powermaster
  • Durable and robust
  • Due to pipe diameter, usually 50-100mm, the pump can draw water from very narrow sumps.
  • Up to 6 hours of continuous pumping based on a 5 litre fuel tank.
  • Depending on the specific type of fuel pump (trash, slurry or clean water), can pump suspended solids of up to 32mm

Disadvantages of fuel driven pumps

  • Cannot be used indoors, carbon monoxide exhaust fumes can be harmful
  • Suction depth (the difference between the pump inlet and water level) is limited to between 1 and 3.5m
  • Fuel contamination is a possibility
  • A petrol pump needs to be serviced; a pump that works in dusty area will need to be serviced more regularly than a pump that works in a ‘clean air’ environment.
  • Fuel driven pumps could be a fire hazard
  • Pump unit must be primed before use

It is worth noting that there are two types of fuel driven pumps, petrol and diesel. Diesel driven pumps are considerably more expensive, in some cases double the cost, because they: have a lot fewer spare parts than that of petrol, therefore spare parts are more readily available; are a lot more robust and reliable; have lower fuel consumption; are safer to operate due to diesel having a lower flash point, and is therefore less flammable.

Electrical submersible drainage pumps

Drainage pumps are a sealed pump unit that is installed under water, with the use of an electrical motor that rotates the shaft and in turn the impellor, water is drawn in through the bottom of the pump and then pumped through a delivery hose, no smaller than 50mm, out of the desired area. These pumps usually come complete with a float switch connected so that unit that will automatically switch off the pump if the water level gets too low.

Advantages of a drainage pump:

  • Easy installation: no suction hoses required, only a delivery hose
  • Pumping heads up to 12m
  • Can be used in all-weather conditions
  • Pumping solids up to 50mm, depending in pump type, therefore up to Category 3 wastewater can be pumped.
  • No priming needed

Disadvantages of a drainage pump:

  • Limited pressure
  • Power supply needed
  • Bulkier, so space limitations apply
  • Drainage pumps that have a float switch are not to be used in continuous duty applications.

 


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