Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

Static Pressure in a HVAC System

A minimum static pressure is required in a HVAC system to keep the water in the highest levels of the system.

Sponsored Links

The static pressure in most HVAC systems is a result of the height of the building plus a cushion at the top of the building. In general the cushion is around 5 - 10 psi (lb/in2) or 10 - 20 ft (3 - 6 m) water column.

Static Pressure as Head (ft, m)

The static pressure can be expressed as head:

hs = hb + hc                                                     (1)


hs = static head (ft, m)

hb = elevation at the top of the building (ft, m)

hc = cushion required at the top of the building (ft, m)

Static Pressure as Pressure - (psi)

ps = hb + hc / (144 / γ)                                                 (2)


ps = static pressure (psig)

γ = specific weight of water at the operating temperature (lb/ft3)

Example - Static Pressure in a Water Heating System

The static head of a 190 ft tall building and cushion head 10 ft can be expressed as calculated as:

hs = (200 ft) + (20 ft)

    = 220 ft

With water operating temperature 60oF and specific weight 62.4 lb/ft3 - the static pressure can be expressed as:

ps = (200 ft) + (20 ft) / (144 / (62.4 lb/ft3) )

    = 95.3 psig

Sponsored Links

Related Topics

Related Documents

Sponsored Links

Engineering ToolBox - SketchUp Extension - Online 3D modeling!

3D Engineering ToolBox Extension to SketchUp - add parametric components to your SketchUp model

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro .Add the Engineering ToolBox extension to your SketchUp from the SketchUp Pro Sketchup Extension Warehouse!

About the Engineering ToolBox!


We don't collect information from our users. Only emails and answers are saved in our archive. Cookies are only used in the browser to improve user experience.

Some of our calculators and applications let you save application data to your local computer. These applications will - due to browser restrictions - send data between your browser and our server. We don't save this data.

Google use cookies for serving our ads and handling visitor statistics. Please read Google Privacy & Terms for more information about how you can control adserving and the information collected.

AddThis use cookies for handling links to social media. Please read AddThis Privacy for more information.


This page can be cited as

  • Engineering ToolBox, (2004). Static Pressure in a HVAC System. [online] Available at: [Accessed Day Mo. Year].

Modify access date.

. .


3D Engineering ToolBox - draw and model technical applications! 2D Engineering ToolBox - create and share online diagram drawing templates! Engineering ToolBox Apps - mobile online and offline engineering applications!

Scientific Online Calculator

Scientific Calculator

3 10

Sponsored Links