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How to choose a submersible pump for a well?
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The right submersible pump for proper needs
The selection criteria differ depending on the characteristics of water pumping needs (depth, type of liquides, use of the pumped water). In fact, each type of pump has its own construction characteristics depending on whether we look for pumping in a drill hole, well or groundwater table, water pumping used for a collector, emptying a cellar or even pumping in a cistern or water tank.
The purpose of this article is to provide assistance to specific choice of feed pumps submerged in a well in order to create drinking water system or for a domestic installation.
Should you choose a feed pump submerged in a well or a surface pump?
Apart from exception, beyond 8 meters deep, the surface pumps are no longer suitable in terms of power. It is better to choose a compact submersible
In terms of denominations, we generally distinguish the bore-hole pumps which purpose is to collect water improper for consumption but certified for domestic use (toilet, watering, washing machine), well pumps capable of feeding the dwelling with drinking or non potable wate
Should you choose a submerged pump or a surface pump for well pumping? The submersible pump located by definition under the waterline, is silent (noise absorbed by the water) and does not need any technical room (for weather protection) outside the well. It avoids the costs associated with technical room that has to be watertight to prevent the surface pumps from damage on the long term.
Apart from exceptions, beyond 8 meters of depth, the surface pumps are no longer suitable in terms of power. It is best to choose a compact submersible pump that won’t have any difficulties
pump which will have no difficulty to repress at important gauge height for high flow/pressure performances. At this depth the submersible pump is protected from freezing, in contrast to the surface pump which has to be drained and insulated in winter.
The pump body (and so the electric motor) are immersed in the water. The pump is cooled naturally, avoiding all risks of overheating. This close proximity to water allows the pump to be in charge permanently. The risk of a pump decommissioning due to a leak (faulty valve, …) of the back-flow system are thus avoided. When the objective is to connect to a domestic system, the infrastructure needed (bladder reservoir, etc.) is comparable in both cases.
That’s why, for well water collection purposes, we recommend choosing a submersible pump.
Important parameters for choosing a pump submerged in a well
Follow our methodology below, so you can easily determine the submersible pump appropriate for your situation:
- Typology of the water to be sucked. What is the size of solids in water? Does the required pump have to repress clear water (< 4-5 mm) or dirty water (< 10 mm)? This characteristic is essential for not clogging the pump body and damage it prematurely. The clear waters are mostly runoff waters and rainwaters. The dirty waters are in the case of a well sandy waters.
Picture source: POMPES JETLY
- What is the minimum flow required (Q in m³/h)? It empirically matches the daily consumption divided by 3.
- For a house it is necessary to count with 200 litres per person for a domestic use. House of 5 people = 1000 litres/day. That is an instantaneous flow of 3 m³/h for the pump. Average domestic water supply in function of the household: 2 to 4 m³/h
- For automatic watering count 8 litres per m2 per day. A garden (grass, garden) of 500 m² will need 4000 litres (4 m3), a pump flow of approx. 1.5 m³/hour. Sprinkler systems: 1.5 m³/h per sprinkler.
- What is the total head (TH in meters of water column) of the installation?
- The manometric head for a submerged pump = elevation difference (1) + pressure drop (2) + useful pressure (3)
- (1) the maximum back-flow height (in meters) = elevation difference = distance between the pump at the bottom of the well and the highest draw off point
- (2) the pressure drop (in meter) related to frictions in the pipes (bends, junctions, etc.):
- it is necessary to know the flow rate, the diameter and the total length of the back-flow pipe. Then the loss is determined by the chart attached.
- Example: Flow 2 m³/h, pipe diameter 1″ (26×34), pipe length 100 m. Pressure loss (m) = 9 cm/m x 100 m = 9 m
- it is necessary to know the flow rate, the diameter and the total length of the back-flow pipe. Then the loss is determined by the chart attached.
- (3) the highest useful pressure at the outflow of the draw off point:
- Outside tap – usually 2.5 bars = 25 m, shower 3 bars = 30 m, sprinkler 3 bars per sprinkler = 30 m.
- Example (domestic use): HMT = 7 meters (well depth) + 3 meters (floor tap) + 5 meters of pressure loss (pump 3m³/h) + 25 meters (operating pressure) = 40 m. The diagram below shows that the pump Idramatic provides more than 3 m³ flow rate for a manometric delivery head of 40 m. It is therefore appropriate to the need.
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- The pressure decrease the greater the well depth is, it is appropriate to choose the right power of the pump in function of the well depth and the characteristics of the installation. Each pump is described by a power chart (power, pressure, flow) to which reference should be made to ensure it meets the need.
- What is the diameter of discharge and distribution pipes? The diameter should be choose in correlation with the pump flow. If the nominal flow is too important for the pipelines, you need to increase their diameter or reduce the pump power. See the chart.
- Additional equipment? Will the pump be associated to a booster for providing sufficient pressure for the use (domestic, watering, etc.)? Some submersible pumps provide sufficient pressure independently, obviating any booster.
Best submersible pump choosing guide for shallow wells: our selection
Selection of submersible pumps: performance, quality, durability, innovative features
| Dimensions | Maximum Immersion Depth | Maximum Flow/Pressure | Significant Competitive Advantages | |
|---|---|---|---|---|
| Pump GUINARD model IDRAMATIC 1200 | 800 M² garden + 4 people | 12 meters, clear water | 1200W, 1CV, – 5.5 m³/h for TH max= 65 meters | Efficient, multi-cell (stainless steel pump casing and turbine AISI 304), self-priming, lack of water security function, integrated check valve, automatic anti-lock security every 100 hours, tankless pressure booster, plug & pump, guarantee 3 years. |
| Bore-hole pump 3″ GRUNDFOS SQ 2-70/30M | 200 M² garden + 4 people | 17 meters, clear water | TH max: 88 meters, Max flow: 3,4 m³/h | Integrated protection against dry running, soft start, integrated check valve, under-voltage and over-voltage protection, overheating protection, high efficiency of hydraulics and engine, excellent wear resistance |
Submersible pumps require annual maintenance.
Further information
- The water from wells is usually not drinkable because the filtering of sedimentary rocks is not sufficient to stop the pollution (contaminated rainwater, pesticides, bacterias, nitrates, etc.).
- The pump must not be placed at the bottom of the well (not to suck the sand and dirt), nor placed too close to the well walls. To avoid this, the pump should be suspended using a rope (usually supplied).
- The presence and use of a domestic well (even for watering) must be declared at the town hall. Connection to the home network (toilet, washing machine, etc.) requires a permit and establishment of a parallel evacuation network separated from sewage and rainwater network (in order not to contaminate the urban network of drinking water with polluted water). Since 2009, the law requires the owners to install a meter to record the pumped volumes and to pay a fee.
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