Estimated Design Flow Rate: litres/min
Recommended Minimum Pipe Size: mm
* Results are indicative and assume normal domestic usage diversity.
The Domestic Water Supply Sizing Calculator helps you determine the correct pipe size for residential water supply systems. Proper pipe sizing ensures adequate water pressure, balanced flow at multiple outlets, and reliable performance across the entire property.
Whether you’re designing a new home, upgrading pipework, or solving low-pressure issues, this calculator provides fast, practical guidance based on accepted plumbing principles.
Domestic water supply sizing is the process of selecting pipe diameters that can deliver sufficient water flow to taps, showers, appliances, and fixtures without excessive pressure loss or noise.
Correct sizing depends on:
Number of outlets and appliances
Simultaneous water demand
Pipe length and layout
Water pressure
Acceptable flow velocity
Undersized pipes cause poor pressure, while oversized pipes increase cost and stagnation risk.
A Domestic Water Supply Sizing Calculator estimates the appropriate pipe diameter by analysing demand, flow rates, and system conditions. It helps balance performance, safety, and efficiency while following industry best-practice guidelines.
This tool simplifies complex sizing calculations into clear, easy-to-understand results.
Using the calculator is quick and straightforward:
Select the number and type of water outlets
Enter pipe length and layout details
Input available water pressure
Choose pipe material
Calculate to see the recommended pipe size
The calculator applies standard flow-rate and velocity limits used in domestic plumbing design.
The Domestic Water Supply Sizing Calculator is ideal for:
Homeowners planning plumbing upgrades
Plumbers & installers
Builders & renovation contractors
Mechanical & building-services engineers
Developers & self-builders
Correct pipe sizing helps to:
Maintain consistent water pressure
Allow multiple outlets to run simultaneously
Reduce noise and pipe wear
Prevent excessive pressure loss
Improve system efficiency and lifespan
Proper sizing is essential for modern homes with multiple bathrooms and appliances.
Based on realistic domestic demand assumptions.
Designed for multi-bathroom properties and appliances.
Ensures showers, taps, and appliances work reliably.
Suitable for professionals and non-technical users.
No registration required.
Your results may include:
Recommended pipe diameter
Estimated flow rate
Flow velocity check
Pressure loss guidance
These insights help you confidently select the correct pipe size for each section of your system.
Number of fixtures and appliances
Simultaneous usage patterns
Pipe material and internal diameter
Length of pipe runs
Incoming mains pressure
Each property has unique demand requirements.
Whole-house cold water supply
Hot water distribution
Multi-bathroom properties
Kitchen and utility connections
Renovation and extension projects
Avoid undersizing main supply pipes
Limit excessive pipe velocities
Keep pipe runs as short and direct as possible
Use appropriate pipe materials
Allow for future expansion where possible
Good design prevents performance problems later.
The calculator provides reliable estimates using standard plumbing design assumptions. For complex systems, professional design is recommended.
Yes. It is well suited for modern homes with multiple bathrooms and appliances.
Yes. It supports both cold and hot water supply sizing.
Yes. Undersized pipework is a common cause of poor pressure.
Yes. You can adjust inputs to reflect existing pipe layouts and demand.
No. It is a guidance tool and should be used alongside professional judgement.
Results are guidance only and not a substitute for full system design.
Local plumbing regulations may vary.
Always confirm final pipe sizes with applicable codes and standards.
Use the Domestic Water Supply Sizing Calculator to ensure reliable water flow, balanced pressure, and efficient plumbing performance throughout your home.