# Why is Static Pressure Important?

Static pressure is the maximum pressure that you can expect in the system. It is caused by water being 'static,' i.e. there is no flow rate.

What is static pressure?

The maximum pressure that you can expect in the system.

What causes static pressure?

It is caused by water being ‘static,’ i.e. there is no flow rate.

When is a water system static?

A water system operates anywhere between the following flow rates:

• Peak – such as 8am when everyone is showering before work
• Static – such as in the middle of the night when no one is using water

Therefore, the system is’ static’ when no one is using the water.

How does the flow rate affect the pressure?

When the flow rate decreases, the pressure increases.

When the flow rate decreases all the way down to 0 L/s (static), the pressure increases to its highest possible point.

Why does static pressure matter?

Every component in a water system has a maximum inlet pressure.

If the pressure in the system exceeds the maximum inlet pressure, the following occurs:

1. The warranty of the component(s) will be void
2. The component (pipe/valve/taps) will not function properly
3. The system design will be non-compliant

What static pressure should I design?

The typical maximum inlet pressure for components is:

• TMV – 500kPa
• RPZ – 1600kPa
• Fixtures – 500kPa
• 50mm Copper Pipe – 1710kPa
• 50mm Steel Pipe – 6800kPa

Prior to undertaking your design, to ensure your design meets the correct maximum pressure, you should always check:

1. The technical data sheet of the products that you are using
2. The requirements in your local standards

How to calculate static pressure?

The information you require for your calculations is:

1. The maximum pressure at the water connection
2. The height difference between your water connection and the component

Note that flow rates, velocities, pipe sizes, etc. do not have any effect on the static pressure.

Example

In this example, we will be calculating the static pressure at the highest and lowest fixtures in the building.

1. Water Connection

The water connection properties are:

Height: -1m

Static Pressure: 420kPa

2. Fixture Heights

Highest Fixture: 13m

Lowest Fixture: -11m

3. Height Difference

For every 1m change in height, the pressure changes by approximately 9.81kPa (due to Earth’s gravity).

As water goes up the building, the pressure decreases 9.81kPa per metre.

As water goes down the building, the pressure increases 9.81kPa per metre.

4. Highest Fixture Pressure Calculation

Height Difference = Highest Fixture Height (13m) – Water Connection Height (-1m)

Height Difference = 13m – -1m

Height Difference = 14m

Pressure at Highest Fixture = Pressure at Water Connection (420kPa) – Height Difference (9.81kPa * 14m)

Pressure at Highest Fixture = 420kPa – 137.34kPa

Pressure at Highest Fixture = 282.66kPa

5. Lowest Fixture Pressure Calculation

Height Difference = Lowest Fixture Height (-11m) – Water Connection Height (-1m)

Height Difference = -11m – -1m

Height Difference = 10m

Pressure at Lowest Fixture = Pressure at Water Connection (420kPa) + Height Difference (9.81kPa * 10m)

Pressure at  Lowest   Fixture = 420kPa + 98.1kPa

Pressure at Lowest Fixture = 518.1kPa

6. Conclusion

Fixtures generally have a maximum inlet pressure of 500kPa.

The static pressure at the lowest fixture is 518.1kPa which exceeds the maximum inlet pressure.

Therefore, a pressure reduction valve will be added to the design to ensure the pressure does not exceed 500kPa.

h2x automates the pressure calculations based on the inputs from the water connection and the heights assigned to your fixtures/nodes.

H2X will also provide warnings where the pressure exceeds the component(s) maximum inlet pressure.

The video below explains the design and calculation process using H2X:

H2X was built by engineers to help engineers work faster, better and more effectively.

If you would like to try H2X today, sign up for a 14-day free trial now.

## What's in the Pipeline?

Get technical resources delivered to your inbox weekly!

##### CASE STUDIES
###### Award-Winning Heating Design

"Using h2x was pivotal, allowing for precise heat loss calculations, pipe sizing and flow rates for each room.

This level of detail ensured that the heating load accurately matched each space's requirements, minimising energy waste and maximising comfort.

The strategic placement of heat pumps and careful sizing of pipework were crucial in maintaining minimal pressure drops over an 18-metre distance."

##### CASE STUDIES
###### Greengate, UK

"I would estimate over the length of this project, I have spent 50% less time designing than I would on our previous software.

The ability to output the design straight into Revit assisted clash detection and coordination."

##### CASE STUDIES
###### Salon Republic, USA

"The quality of the designs saw significant improvement with the adoption of h2x."

"The software offers precision through detailed result outputs and advanced options for efficient pipe sizing, allowing heating engineers to optimise based on parameters like maximum velocity and pressure drop."

Testimonials

What Installers Say

What Consultants Say

A game changer for the humble plumber. Incredible.

Director at Queenstown Plumbing

Brilliant, simple and easy to use. Game changer.

James Major

Director at Hubb

Big time game changer to the industry!

Viv Jude

Director at UHC

Incredible software! Super user-friendly and allows you to save so much time.

Devni Gamage

Engineer at DMA

h2x is great software, our company use it nearly every day. It is easy to use with direct conversion from h2x to Revit.

Callum Craig

Engineer at WDE

h2x is fantastic software. It is very easy to use and the ability to output to Revit is a fantastic time saver.

Joe Kirrane

Engineer at MEP