What pump power do I need for a home water well?

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What pump performance do I need for my home water supply?

This is probably the most common question customers bring when choosing a home water supply system. And it's precisely where the most mistakes are made – people either buy a too weak pump that cannot supply the whole house, or on the contrary, an unnecessarily strong one that always has pressure but unnecessarily increases the investment and consumes more electricity. In this article, we will look at how to correctly calculate the required performance, which parameters are really decisive, and what we recommend to customers in practice when they cannot make up their minds themselves.

An important note right at the beginning: the pump power (given in watts or kilowatts) is not the main parameter you decide on. Much more important is the hydraulic power – that is the combination of flow rate (Q, in l/min or m³/h) and delivery head (H, in meters). The wattage is only a reflection of the electrical demand, not what the pump can actually do.

What do we mean by "performance" of a pump – basic terms

Before we get into the calculations, we need to explain the terminology. In technical practice, we come across two different "performances":

Input power (P1) – how much electrical energy the pump consumes. It is given in watts (W) or kilowatts (kW). For example, 550 W or 0.55 kW.
Hydraulic power (P2) – how much energy the pump actually delivers to the water. It is always lower than P1, because no machine has 100% efficiency. The ratio P2/P1 = efficiency (η).
Flow rate (Q) – the volume of water the pump delivers per unit of time. It is given in liters per minute (l/min) or cubic meters per hour (m³/h). 1 m³/h = 16.67 l/min.
Delivery head / manometric head (H) – the total resistance the pump must overcome. It includes the height difference (static head) and pressure losses in the piping (dynamic losses). It is given in meters of water column (mWs) or in bars (1 bar ≈ 10 m).

From these parameters comes the so-called pump characteristic curve (Q-H curve), which shows how the delivery head changes depending on the flow rate. The more water we pump, the lower the pressure the pump can maintain – this is a physical law that no pump on the market can avoid.

Step 1: Determine the required water flow

The first and most important step is to find out how much water your home actually needs. This is determined by the number of draw-off points and their simultaneous operation. In practice, not all taps are opened at the same time, so the so-called simultaneity of draw-off is used – we calculate only a part of the draw-off points that can be active at the same time.

Approximate consumption of individual draw-off points:

Draw-off point	Flow rate (l/min)	Flow rate (m³/h)
Kitchen tap	8 – 12	0.5 – 0.7
Basin / WC filling	6 – 10	0.4 – 0.6
Shower	8 – 15	0.5 – 0.9
Bath	15 – 20	0.9 – 1.2
Garden tap / hose	12 – 20	0.7 – 1.2
Washing machine / dishwasher	10 – 15	0.6 – 0.9
Flush toilet	6 – 8	0.4 – 0.5

As a working formula, it holds: for a family home with 3 – 5 people, the typical flow rate requirement of the pump is 40 – 60 l/min (2.4 – 3.6 m³/h), and in practice, I recommend taking the upper limit as a basis and adding another 15 – 20 % as a reserve. For a smaller home with 2 – 3 people and no garden equipment, 25 – 40 l/min is sufficient.

Step 2: Calculate the required delivery head

The delivery head is the second key parameter. You must overcome:

Static head (Hs) – the height difference between the water level in the well/bore and the highest draw-off point in the house. For example: the water level is 8 m below ground, the house has one floor, the roof height is 2.5 m → Hs = 8 + 2.5 = 10.5 m.
Pressure losses in the piping (Hp) – depend on the pipe diameter, length, number of elbows and fittings. For standard installations with HD-PE or PPR pipes of diameter 25 – 32 mm and length up to 50 m, calculate with 5 – 15 m.
Minimum required pressure at the outlet (Hmin) – for comfortable use and proper function of the water heater or pressure tank, the minimum is 15 – 20 m (1.5 – 2 bar). For showers with thermostatic mixers and modern fittings, I recommend at least 25 m (2.5 bar).

Total required delivery head: H_total = Hs + Hp + Hmin

Practical example: a well with a water level 6 m below ground level, a house with a ground floor and an attic (height 5 m), 40 m of pipe, 25 mm diameter. Hs = 11 m, Hp ≈ 8 m, Hmin = 20 m → H_total = 39 m. The pump must have a delivery head of at least 40 m at the required flow rate.

Step 3: Find a pump with the appropriate performance curve

Now you have two numbers: the required flow rate Q and the required delivery head H. From the Q-H curve of the pump, you must verify that the pump actually achieves your H at your Q – and ideally with a reserve of at least 10–15%. The operating point should be in the central part of the Q-H curve (not at its edges), where the pump is most efficient.

Examples from our range: if you have a well with a water level up to 8 m and need to supply a smaller house (2–3 people, flow rate approx. 30 l/min, H approx. 30–35 m), the excellent choice is the domestic water supply system with submersible pump 3 SQIBO 0,55 / 50l, which is specifically designed for drinking water from shallow wells. For more demanding applications – a deeper well, a larger house, a garden – I recommend considering the water supply system with pump 3 SQIBO 0,75 / 50l, where the higher power (0.75 kW) provides significantly better delivery head and flow rate.

Customer types and their typical performance requirements

After years of experience with the installation of domestic water supply systems, I know that most situations fall into a few categories. Take a look and see which one fits you:

Cottage or weekend house (1–2 people, minimal points of use)

Typically 1 bathroom, kitchen, maybe a garden tap. Water level in the well 3–6 m. Required flow rate: 20–30 l/min. Delivery head: 20–30 m. A pump with a power of 0.37–0.55 kW will be sufficient. A smaller pressure tank (24–50 l) is adequate. An ideal choice is, for example, the water supply system with submersible pump SCR-0,50 / 50l, which is also suitable for garden irrigation.

Family house (3–5 people, standard bathroom + kitchen)

2–3 bathrooms, washing machine, dishwasher, garden tap. Water level 5–15 m (well or shallow borehole). Required flow rate: 40–60 l/min. Delivery head: 35–50 m. Pump power: 0.55–0.75 kW. Pressure tank 50–80 l. I recommend leaving some room and choosing a pump at the upper limit – it is only a difference of a few dozen euros, but the comfort is significantly higher.

Family house with a deeper borehole (water level 20–50 m)

This is a situation where mistakes are made most often. The customer sees a 0.55 kW pump at a more favorable price and does not buy it. However, at a water level of 25 m and a requirement of 40 l/min, you need a delivery head of at least 50–60 m – and here 0.55 kW simply does not suffice. You need to go for 0.75 kW and, for deeper boreholes (40+ m water level), consider 1.1–1.5 kW pumps with multi-stage pumping.

House with a large garden or garden irrigation

Garden irrigation is a huge consumer. A garden hose consumes 12–20 l/min, a sprinkler 8–15 l/min, and a drip irrigation system can be up to 30 l/min on a larger garden. If you plan to supply the garden from the well via a water supply system simultaneously with the house, add an additional 20–40 l/min to the basic calculation. This practically means choosing a more powerful system.

Impact of well or borehole depth on pump selection

Well depth is one of the parameters that customers most often underestimate. It is important to understand that the pump's head does not depend on the total depth of the well/borehole, but on the actual water level during pumping (i.e., the dynamic level, not the static one). The dynamic level is always deeper than the static one – during pumping, the water level drops, and if the pump draws water faster than the well can replenish it, the level drops significantly.

Example: a well is 12 m deep, with a static water level 4 m below ground level. However, during intensive pumping, the level drops to 8 m. If you use the static level (4 m) in your calculation, you will underestimate the pump requirements. Always work with the dynamic level (8 m), or at least allow a reserve of 3 – 5 m above the static level.

For boreholes with a water level deeper than 20 m, I always recommend submersible pumps in a 3" (three-inch) configuration. Surface pumps have a physical suction limit of about 7 – 8 m (the theoretical maximum is 10.3 m). More on this topic can be found in the article Surface vs. submersible water pump: which is better for my water source?

Pressure tank: how it affects pump selection

The pressure tank is an inseparable part of any water pump system. Its volume directly affects how often the pump cycles on and off. A small pressure tank (e.g., 24 l) with a higher consumption profile will cause the pump to switch on very frequently – this shortens the motor's lifespan. A larger tank (50 l or more) extends the intervals between switching.

Most of the water pump systems in our range are equipped with 50-liter pressure tanks, which is the correct minimum for a family home. The pressure tank must be set correctly – the pre-charge air pressure (pre-pressure) should be 0.2 – 0.5 bar lower than the pressure switch setting for pump activation. We cover this in detail in the article Pressure tank in a home water pump system: what it does and how to set it up?

An interesting setup for those who need reliable regulation without a pressure switch is the water pump with submersible pump IBO 3 SDM24 / 50l – RTS. The control unit RTS (electronic pressure regulation) replaces the traditional pressure switch and ensures smoother regulation, dry-run protection, and more comfortable operation.

Selection based on specific borehole parameters: 3" diameter

Submersible pumps for wells and boreholes have standardized diameters. The most common for home water pump systems is the 3-inch (3") diameter – the outer diameter of the pump is approximately 88 mm (some versions 76 mm). The borehole must have an internal diameter at least 20 – 25 mm larger than the pump to allow water to flow as a cooling medium between the pump and the borehole wall. You will find out more about the required diameter of your borehole or well in the article What diameter of borehole or well do I need for a 3" submersible pump?

An example of a well-chosen setup for a deep borehole is the home water pump with submersible pump 3Ti-20 / 50l – RTS, designed for wells and boreholes, with RTS electronics and flow and head values suitable for medium-depth boreholes and larger family homes. Thanks to the 3" size, it fits even into narrower boreholes.

Most common mistakes when selecting pump power

Over the years of practice, we have repeatedly seen the same mistakes. Avoid them:

Selecting based on power consumption, not on Q-H parameters. A customer compares 0.55 kW vs. 0.75 kW and buys the cheaper one without checking the actual head at the required flow rate. Two pumps with the same power consumption can have completely different hydraulic characteristics.
Ignoring the dynamic water level. The static level is 3 m, but the dynamic level drops to 9 m during pumping – that is an additional 6 meters the pump must overcome.
Underestimating the length and diameter of the piping. Long, narrow piping causes high pressure losses. 50 m of 20 mm diameter piping at a flow rate of 50 l/min can result in pressure losses of 20 – 25 m.
Not accounting for the garden. A customer calculates for the house but forgets the garden. When watering the garden in summer, there is no pressure in the shower.
Purchasing without knowing the well's yield. Even the most powerful pump will not help if the well cannot replenish the water. The yield of the water source must be at least equal to the pump's maximum flow rate – preferably higher.
Selecting without a power reserve. A pump operating at 100% capacity continuously wears out faster. The ideal operating point is at 70 – 80% of maximum flow.

Practical calculation step by step

Let's summarize this into a simple procedure that anyone can follow without special technical knowledge:

Determine the depth of the water level during pumping (dynamic level). If you don't know it, use the static level + 4 m reserve.
Measure the height of the highest point of water draw above ground level.
Calculate: Hs = depth of water level + height of the highest draw point.
Estimate the length of the piping and add pressure losses: for standard installations, 8 – 15 m.
Add minimum operating pressure: 20 – 25 m (2 – 2.5 bar).
H_total = Hs + losses in piping + minimum pressure.
Determine the required flow rate based on the number of draw points and the number of people.
Find a pump that achieves at least your H_total + 10% reserve at your Q.

Example: a house with 4 people, 2 bathrooms, a garden tap. Dynamic water level 10 m, house height 4 m, Hs = 14 m. Pipe losses (length 35 m, diameter 25 mm): 8 m. Minimum pressure: 22 m. H_total = 14 + 8 + 22 = 44 m. Required flow: 50 l/min (3 m³/h). The pump must achieve a value of H ≥ 44 m at Q = 50 l/min, ideally 48 – 50 m. This corresponds to a pump with a power of 0.75 kW in a three-inch (3") version.

Energy efficiency and operating costs

A more powerful pump consumes more electricity. With a 0.55 kW pump and an average operation of 2 hours per day, this amounts to 0.55 × 2 × 365 ≈ 400 kWh/year. At a price of 0.20 €/kWh, this is approximately 80 € per year. With a 0.75 kW pump, it is 0.75 × 2 × 365 = 547 kWh ≈ 109 € per year – the difference is only 29 € per year, but in return you get significantly higher hydraulic performance.

Also important is the number of starts per hour. Every motor start is a load on the windings and the capacitor. Pumps with an electronic regulator (RTS) start more smoothly and less frequently, which extends their lifespan. If the pump switches more than 20 times per hour, this is a sign that the pressure tank is too small or improperly set. More on this in the article Pressure tank in a home water system: what it is for and how to set it up?

Special situations: irrigation, fire safety, agricultural buildings

Garden irrigation: if you plan to install an automatic garden irrigation system with multiple zones, add the entire irrigation flow to the household consumption – in practice, this can be an additional 20 – 50 l/min. For such applications, it is worth considering a separate pump for the garden or a more powerful unit from the start.

Agricultural buildings and stables: water for livestock, car washing, and technical water – these are consumers with high consumption. For such applications, it is appropriate to calculate the hourly consumption and dimension the pump accordingly. Do not forget that food-grade (drinking water) pumps must be certified for contact with drinking water if the water is also consumed by people. This topic is covered in the article Drinking water from a well via a water system: what must the system and pump meet?

Fire protection: some house projects require a source of fire water. The requirements for flow are completely different here (tens of liters per minute at high pressure), and a standard home water system is not sufficient for this purpose. A special solution is required for fire protection.

Frequently asked questions (FAQ)

Can I use a pump with higher power than needed? Will it damage anything?

A pump that is too powerful in itself will not harm the house, but it has several disadvantages: higher electricity consumption, higher pressure in the system (which can damage fittings and appliances if a pressure-reducing valve is not installed), and the pump operates outside its optimal operating point, which reduces its lifespan. The ideal is a power at which the operating point lies in the middle third of the Q-H curve.

How can I determine the actual power of my old pump if I don't have the documentation?

The easiest way is to measure the flow – fill a container with a known volume (e.g., a 10-liter bucket) and measure the filling time. Flow in l/min = volume / time × 60. You can determine the pressure using a pressure gauge on the discharge pipe. From these two values and the Q-H curve of a typical similar pump, you can estimate your situation. Alternatively, we can help you identify it based on a photo of the label.

Why is my water pump not creating enough pressure, even though it has sufficient power?

The most common cause is an improperly set pressure tank (low pre-charge air pressure) or a clogged inlet filter/screen on the pump. Another cause may be a worn impeller, which needs to be replaced. Rarely, the cause is air in the system. The article Home water pump not pumping or losing pressure: causes and solutions systematically covers these causes.

Is there a difference between a pump for drinking water and one for irrigation?

Yes, it is essential. Pumps for drinking water must be made from materials approved for contact with drinking water (stainless steel, food-grade plastic, without dangerous copper alloys). Pumps marked only as "for irrigation" or "for utility water" may not meet these conditions. If you want drinking water, always choose a pump with a certificate for drinking water – for example, the 3 SQIBO 0.55 / 50l water pump for drinking water is specifically designed for this purpose.

How much does it cost to operate a home water pump annually?

For a typical family home with a 0.55 – 0.75 kW pump and operation of 1.5 – 2.5 hours per day, we estimate an annual electricity consumption of 300 – 550 kWh, which at an average price of 0.20 €/kWh amounts to 60 – 110 € per year. You should also add occasional maintenance (replacing the membrane in the pressure tank every 3 – 5 years, approximately 30 – 60 €, or replacing the contacts of the pressure switch).

Can I connect two pumps in parallel to double the flow?

Technically yes, but in practice it is not that simple. Connecting two identical pumps in parallel increases the flow (not the head) under the condition of a proper hydraulic design (check valves on each discharge, balanced networks). This is not recommended for DIY installers – it is much simpler and more reliable to choose a single more powerful pump from the start.

Conclusion: pump power is the result, not the starting point

Selecting the power of a home water pump is not a matter of intuition or a simple estimate of "I'll take a stronger one, that should be enough". It is the result of specific calculations based on your situation: the depth of the water source, the height difference, the length of the piping, and the actual consumption requirements of the household. If you know these numbers, selecting a pump becomes a trivial step – you just find a model whose Q-H characteristic meets your requirements with a reasonable reserve.

If you are unsure about the calculations or do not have all the input information (for example, you do not know the exact depth of the water level during pumping), it is better to choose a pump with slightly higher power and a larger pressure tank – the price difference is small, but the comfort and reliability of the system are significantly higher. And if you are planning an installation, don't forget to read the article Installation of a home water pump with a submersible pump step by step, where you will find the entire process from starting the pump in the borehole to the first start-up.

Do you have a question about this topic?

Not sure how to decide or dealing with a specific situation in your household? Write to us – we are happy to help.