Calculation of diameter, capacity and hydraulic parameters of water pipes
The water pipe calculator is designed to calculate the basic hydraulic parameters of pipeline systems. The tool allows you to determine the optimal pipe diameter, throughput, pressure loss and other important characteristics for the design of plumbing systems.
The calculator uses proven hydraulic formulas and calculation methods that take into account all system parameters: pipe diameter, water flow, flow speed, pipe material, surface roughness, fluid viscosity and flow regime. This allows you to obtain accurate results for the design of plumbing systems of any complexity.
Let's look at practical examples of calculating the parameters of water pipes for various use cases:
Water supply for a private house with a flow rate of 50 l/s
Входные данные:
Flow: 0.05 m³/s (50 l/s)
Speed: 2 m/s
Material: PPR
Length: 50 mРасчёт:
D = √(4×0.05/π×2) = √(0.2/6.28) = √0.032 = 0.18 m = 180 mm
Round up to standard: 200 mm
Speed check: V = 4Q/(πD²) = 1.59 m/s (normal)Результат:
Diameter: 200 mm, Speed: 1.59 m/s
Тип:
Private house
The standard diameter for residential buildings is 15-25 mm, but for the highway we use 200 mm
Checking the capacity of a 150 mm pipe
Входные данные:
Diameter: 150 mm (0.15 m)
Speed: 1.5 m/s
Material: Steel
Length: 100 mРасчёт:
Sectional area: A = π×0.15²/4 = 0.0177 m²
Flow: Q = A×V = 0.0177×1.5 = 0.0265 m³/s
Q = 26.5 l/s = 95.4 m³/hРезультат:
Flow: 26.5 l/s (95.4 m³/h)
Тип:
Existing pipe
Enough to supply water to a small building
Calculation of pressure loss in a water supply system of 200 m
Входные данные:
Length: 200 m
Diameter: 100 mm
Flow: 0.02 m³/s (20 l/s)
Material: Plastic (roughness 0.0015 mm)Расчёт:
Speed: V = 4×0.02/(π×0.1²) = 2.55 m/s
Re = 1000×2.55×0.1/0.001 = 255,000
Friction coefficient: λ = 0.016
Losses: ΔP = 0.016×(200/0.1)×(1000×2.55²/2) = 0.104 barРезультат:
Pressure loss: 0.104 bar
Тип:
Long pipeline
Losses within acceptable limits for plastic pipes
Comparison of steel and plastic pipes
Входные данные:
Diameter: 100 mm
Length: 100 m
Flow: 0.01 m³/s
Steel: roughness 0.045 mm
Plastic: roughness 0.0015 mmРасчёт:
Scort: V = 1.27 m/s
Stal: Re = 127,000, λ = 0.025, ΔP = 0.2
Plastic: Re = 127,000, λ = 0.018, ΔP = 0.14Результат:
Steel: 0.2 bar, Plastic: 0.14 bar
Тип:
Comparison of materials
Plastic pipe has 30% lower losses
Plumbing for a 10-story building
Входные данные:
Flow: 0.3 m³/s (300 l/s)
Speed: 2.5 m/s
Material: Steel
Length: 500 m
Number of floors: 10 floorsРасчёт:
D = √(4×0.3/π×2.5) = √(1.2/7.85) = √0.153 = 0.39 m = 390 mm
Running: 400 mm
Checking: V = 4×0.3/(π×0.42) = 2.39 m/sРезультат:
Diameter: 400 mm, Speed: 2.39 m/s
Тип:
Multi-storey building
Large diameter required for high flow
Pipeline for heating system
Входные данные:
Flow: 0.08 m³/s (80 l/s)
Speed: 1.8 m/s
Material: Copper
Length: 150 m
Temperature: 80°CРасчёт:
D = √(4×0.08/π×1.8) = √(0.32/5.65) = √0.057 = 0.24 m = 240 mm
Rounding: 250 mm
At 80°C: 15% less lossРезультат:
Diameter: 250 mm, Speed: 1.63 m/s
Тип:
Heating system
High temperature reduces viscosity and loss
The calculation is based on the laws of hydraulics and includes:
Our water pipe calculator provides many benefits:
The calculator uses proven hydraulic formulas and takes into account all factors: diameter, flow, speed, material, roughness and flow conditions for the most accurate results.
Correct calculation of the diameter helps to choose the optimal pipe and avoid waste of materials, which significantly reduces the cost of the project.
Knowing in advance the required diameter and pressure loss, you will be able to correctly design the system, avoiding installation errors.
A simple interface and quick calculations allow you to get all the necessary data in a few seconds without complex calculations and formulas.
To correctly select and calculate water pipes, it is important to take into account many factors that affect the operation of the system.
The pipe diameter is selected based on the required water flow, permissible flow rate and pressure loss. For residential buildings, pipes with a diameter of 15-25 mm are usually used, for industrial facilities - up to 200 mm or more. Use the formula D = √(4Q/πV), where Q is flow (m³/s), V is speed (m/s).
The throughput capacity depends on the pipe diameter, material, internal surface roughness, fluid viscosity, temperature and flow regime (laminar or turbulent). The larger the diameter and the lower the roughness, the higher the throughput.
Pressure loss is calculated using the Darcy-Weisbach formula: ΔP = λ × (L/D) × (ρV²/2), where λ is the friction coefficient, L is the pipe length, D is the diameter, ρ is the density, V is the speed. Local resistances (fittings, fittings) are also taken into account, which increase losses by 20-30%.
Laminar mode (Re < 2300) is characterized by smooth fluid flow with low energy losses. Turbulent mode (Re > 4000) occurs at high speeds and is characterized by vortex motion with increased pressure losses, but a more stable flow.
The choice of material depends on the operating conditions. Plastic pipes (PVC, PPR) are suitable for cold water and have low pressure losses. Metal-plastic - for hot water, copper pipes - for heating systems, steel - for high pressures and industrial systems.
The flow rate is calculated using the formula: Q = A × V = πD²V/4, where A is the cross-sectional area, V is the flow velocity, D is the pipe diameter. For example, for a pipe with a diameter of 100 mm at a speed of 2 m/s: Q = π×0.1²×2/4 = 0.0157 m³/s = 15.7 l/s.
The optimal flow speed for water supply is 1.5-2.5 m/s. A speed of less than 1 m/s can lead to stagnation and sedimentation; a speed of more than 3 m/s increases pressure loss and noise in the system.
The roughness of the inner surface of the pipe directly affects the coefficient of friction and pressure loss. Plastic pipes have a roughness of 0.0015-0.007 mm, steel - 0.03-0.05 mm, cast iron - 0.1-0.3 mm. The higher the roughness, the greater the pressure loss.
The Reynolds number is calculated by the formula: Re = ρVD/μ, where ρ is the density of the liquid (1000 kg/m³ for water), V is the flow velocity (m/s), D is the pipe diameter (m), μ is the dynamic viscosity (0.001 Pa s for water). Re < 2300 - laminar mode, Re > 4000 - turbulent.
The permissible pressure loss in the water supply system should not exceed 0.2-0.3 bar per 100 m of length for normal operation of the system. For systems with a pump, losses may be higher, but should not exceed 0.5 bar per 100 m.
For a multi-storey building, the diameter is selected based on the total consumption of all apartments. Typically, pipes with a diameter of 50-100 mm are used for the riser, and 100-200 mm for the main line. The calculation is carried out taking into account peak flow and flow speed of 2-2.5 m/s.
Yes, water temperature affects the viscosity and density of the liquid. Hot water (80-90°C) has a lower viscosity (0.0003 Pa s) and lower pressure loss by 15-20% compared to cold water (20°C). For heating systems this is important to consider.
The friction coefficient depends on the flow regime. For laminar flow: λ = 64/Re. For turbulent flow, the Blasius formula is used: λ = 0.316/Re^0.25 or the Colebrook-White formula to take into account roughness: 1/√λ = -2log(ε/(3.7D) + 2.51/(Re√λ)).
Local resistances include fittings (bends, tees), valves, taps, gate valves, filters. Each element increases pressure loss by 5-15% of the dynamic pressure. For accurate calculations, local resistance coefficients ξ are used.
For a heating system, the diameter is selected based on the thermal load and temperature difference. Typically, pipes with a diameter of 20-40 mm are used for a private house, and 50-150 mm for a multi-story house. It is important to take into account the lower viscosity of hot water.
The required pump pressure is calculated as the sum of the geometric lift height, pressure loss in the pipeline and local resistance, plus a margin of 10-15%. H = Hgeom + ΔP/ρg + Nlocal + Nreserve. For a residential building, a head of 30-50 m is usually required.
Yes, but it is important to choose the right type of plastic. Polypropylene pipes (PPR) with reinforcement are suitable for hot water up to 95°C. Polyethylene (PE) and PVC pipes are not suitable for hot water - they deform at temperatures above 60°C.
For a private house, the diameter is calculated based on the number of water points and peak flow. Typically, pipes with a diameter of 15-25 mm are used for branches and 25-32 mm for the main. At a flow rate of 0.05 m³/s (50 l/s) and a speed of 2 m/s, a diameter of about 180 mm is required for the line.
Basic formulas: continuity equation Q = A×V, Darcy-Weisbach formula for pressure loss, Reynolds number Re = ρVD/μ, Hazen-Williams formula for quick calculations: V = 0.849C×R^0.63×S^0.54, where C is the roughness coefficient.
It is recommended to choose a diameter with a margin of 10-15% of the calculated value. This compensates for losses in fittings, possible blockages, future increases in load and ensures stable operation of the system under non-standard operating conditions.
Internal diameter (Din) is the diameter of the pipe flow section, used for hydraulic calculations. Outer diameter (Dout) - the external size of the pipe, takes into account the wall thickness. For calculations, the internal diameter is always used: Din = Dout - 2×S, where S is the wall thickness.
In a system with parallel branches, the pressure loss in each branch is the same, but the flow is distributed proportionally to the resistance. For successive sections, losses are summed up. Use the equivalent length principle or cost balancing method.
Standard diameters of water pipes: 15, 20, 25, 32, 40, 50, 63, 75, 90, 110, 125, 140, 160, 200, 250, 315, 400 mm. For steel pipes: 15, 20, 25, 32, 40, 50, 65, 80, 100, 125, 150, 200 mm. The diameter is selected depending on the flow rate and flow rate.
Pressure loss is proportional to the length of the pipeline according to the Darcy-Weisbach formula. For every 100 m of length under standard conditions, 0.1-0.3 bar of loss is added. Therefore, it is important to minimize the length of the pipeline and use straight sections without bends.
The flow rate is calculated as the sum of the flow rates of all water withdrawal points, taking into account the simultaneity factor. For residential buildings, the simultaneity coefficient is 0.6-0.8. Consumption of one point: faucet - 0.2 l/s, toilet - 0.1 l/s, shower - 0.15 l/s, washing machine - 0.3 l/s.
Steel pipes have pressure losses 30-50% higher than plastic pipes due to greater roughness (0.045 mm versus 0.0015 mm). Under the same conditions, a plastic pipe with a diameter of 100 mm has a loss of 0.14 bar, a steel pipe - 0.2 bar per 100 m of length.
For a well, the diameter is selected based on the well's flow rate and the required flow rate. Typically, pipes with a diameter of 25-50 mm are used for private wells and 100-200 mm for industrial ones. It is important to take into account the losses in the suction pipe and the required pump pressure.
The hydraulic slope is calculated as the ratio of pressure loss to the length of the pipeline: i = ΔH/L = (λ×V²)/(2g×D), where ΔH - pressure loss (m), L - length (m), λ - friction coefficient, V - speed (m/s), g - gravitational acceleration (9.81 m/s²), D - diameter (m).
The choice of diameter is influenced by: required water flow, permissible flow speed (1.5-2.5 m/s), permissible pressure loss (0.2-0.3 bar per 100 m), pipe material, pipeline length, number of water points, peak flow, presence of a pump and its characteristics.
The correctness of the calculation is checked: the flow speed must be in the range of 1.5-2.5 m/s, the pressure loss must not exceed 0.2-0.3 bar per 100 m, the Reynolds number must correspond to the flow regime, the diameter must be from the standard range, the flow rate must correspond to the required one.
For a fire extinguishing system, the diameter is calculated based on the required water flow to extinguish the fire (usually 5-10 l/s per point) and the number of points simultaneously. Use pipes with a diameter of 65-150 mm for the main line and 50-80 mm for branches. It is important to ensure sufficient pressure.
The basic formula for calculating the diameter: D = √(4Q/πV), where Q is the flow rate (m³/s), V is the speed (m/s). To check, use the flow formula: Q = πD²V/4. For pressure loss: ΔP = λ×(L/D)×(ρV²/2). Diameter is rounded to the nearest standard value.