Sizing a water pump
In any activity that involves water usage against the gradient, it is ideally to be knowledgeable on water pump sizing. Water pump sizing is the determination of flow rate and the pressure of the pump and its ability to impart pressure against the designated gradient at the required flow rate and pressure. Moreover, on the matters of irrigation and water domestic water usability, it is recommended to initially identify the water source and the designated area to be used.
Water pump sizing is very critical tool for designing plumbing works and irrigation works since it dictates the ability of the pump hence the price. As the rule of thumb, the higher the flow rate, the hydraulic lift (height at which water is to be lifted) and the horse power (power capacity of the pump) the higher the pricing of the pump.
Factors to consider while sizing the pump
- The hydraulic lift
- Suction lift
- Water flow rate and pressure
- Pressure drops
Hydraulic lift is the designated height at which water is to be pump to. For excellent water pump sizing, it is advisable to consider the suction head i.e. the distance between the water surface and the suction port of the pump, delivery head (distance between the discharge port of the pump and the first water emission point.
These water emission points can be water taps, sprinkler heads or water flooding points. For instance, in irrigation purposes, water hydraulic lift can be the summation of suction head and the delivery head (citation)
Suction lift/suction head
This lift is very important since it helps to exert a vacuum in the pipe hence sucking up the water to the pump. Nonetheless, Suction head is normally used to determine the lifting pressure of water pump. The normal water pump suction normally ranges from four meters to six meters. (Citation)
Water flow rate and pressure
Flow rate of water is the amount of water that a water pump can deliver within a unit of time and pressure. Majorly, pump water flow rates are measured in terms of liters per minute (l/min) , liter per second(l/s) or cubic meter per seconds(m3/s) or cubic meter per hour(m3/h).
Water pump flow rates are very essential mostly when designing water usage for either domestic or commercial usage. For irrigation purposes like over head irrigation, the water pump installer must take into consideration the flow rates of irrigation equipment, and the approximated losses in order to accurately design the water pump. When water pumps are not correctly sized, poor water deliveries and lower pressures can be experienced
Water pressure is a measure of the force that pushes water through the mains and into your pipes. It is measured in ‘bars’ – one bar is the force needed to raise water to a height of 10 meters.
Water flow rate depends on the size of your pipe. If several taps or appliances are connected to the same pipe, there will be a lower flow rate and there may not be enough water coming through the pipe for all of the
Water pumps experiences losses of pressure due to leakages along the mains, pump fittings like valves, elbows, tees and the adaptors in the process the pressure drops erupts thus the term pressure drops.
Things to consider when buying water pumps.
Things to consider while buying a pump may include a series of considerations which may need a professional to demystify some facts below are some of the things to check out for
1: Flow rate
Mostly flow rate is measured using the relationship of time and quantity (liters per minute.) Pumps used for sites or farms should have the ability to deliver enough water over a short time so as to take short irrigation hours. The recommended flow rate of over required is above 2500 liters per minute. However, this remains a key factor among things to consider while buying a water pump for irrigation
2: The size of the inlet:
The inlet is the point at which water is drawn from the source into the pumping chamber of the water pump mostly referred to as suction pipe. This is also an important factor to consider while buying a water pump for irrigation. Most pumps have an inlet of 1-6 inches. In some cases, it may be more than 6 inches. The bigger the inlet size, the higher the amount of water the pump will be able to pump out and therefore faster it will take to deliver water into the irrigation system or for domestic purposes
3: Maximum head and pressure:
This refers to the longest distance in terms of vertical height that the pump will be able to pump. The vertical height is brought about by the general inclination of a specific farm ground also referred to as gradient. This also comes in as an important factor to consider while buying a water pump for irrigation or for domestic purposes. The maximum head to choose should be more than the height one intends to pump water. The maximum head and pressure also take care of the work that may be needed along the pumping line, for example, the opening of none return valves that may be mounted along with the system or creating impact in case of sprinkler irrigation
4: The quality of the water pump:
It is important to buy a recognized brand or get a recommendation for a new brand from a qualified irrigation expert. It also requires personal surveys and research. The materials used on the engine and motor may also tell the quality of the pump However it is important to get an irrigation expert while looking for a thing to consider while buying a water pump for irrigation. Some brands have been tested and have been proven over time by a different user. Customer’s testimonies may be a source of information while choosing a quality irrigation pump.
5: The type of water to be pumped:
Water type to be pumped is also a factor to be considered. Things to consider while buying a water pump for irrigation may be affected by the quality of water. Things to consider may include salinity, sand particles, and other foreign matters that may affect the purity of water. The water pump is different from chemical and trash pumps.
The do’s when using and sizing water pump
- Install a foot valve or check valve on the suction line.
- The internal diameter of the pipe must be at least equal to the diameter of the pump port.
- To avoid motor overheating of the water pump, the recommended starting limit should be at least 20 starting/hour without exceeding.
- The water temperature range must be between 0 ºC and 40 ºC.
- Install the pump as close as possible to the liquid source.
- Do not start the pump until it has been completely filled with water
- Fix the pump securely to its base helps absorbing vibrations caused by its operation. Thus the pump must be installed in horizontal position.
Questions to ask when sizing the water the water pump
- What is the Height difference between the pump and the highest point of use?
- Is there any pressure already available? Positive suction?
- Is the water source below the pump? Does the pump have to draw up the water “suction”?
- How far does the pump have to pump water too?
- What size, type and length of Pipe is being used from the Pump to the final destination (Pipe Friction Loss)
- What is the required pressure at the Tap/shower, Sprinkler? if known
- What is the water source?
- What power supply is available?