Water column (WC) and pounds per square inch (PSI) are both ways to measure pressure. You’ll often see WC used for lower pressure systems, especially when dealing with gas pressure in your home. PSI is more common for higher-pressure situations.
This article will explain how to convert from a measurement in inches of water column to PSI, and vice versa.
Understanding Water Column (WC)
Water column (WC) is a unit of pressure. It’s based on how much pressure it takes to raise a column of water to a certain height, usually measured in inches.
The term comes from the old U-tube manometers that technicians used to measure pressure. They’d literally measure the height of a column of water to determine the pressure.
You’ll often see WC used to measure natural gas and propane pressure in homes and some businesses.
The conversion formulas: WC to PSI and PSI to WC
Here are the formulas you’ll use to convert between inches of water column and pounds per square inch.
WC to PSI conversion
To convert from inches of water column to pounds per square inch, use this formula:
PSI = WC ÷ 27.708
In other words, you’ll divide the value you have in inches of water column by 27.708, and that will give you the equivalent pressure in PSI.
Here’s an example: Let’s convert 10 inches WC to PSI. You’ll perform the following calculation:
10 WC / 27.708 = 0.3609 PSI
PSI to WC conversion
To convert from pounds per square inch to inches of water column, use this formula:
WC = PSI x 27.708
In this case, you’ll multiply the PSI value by 27.708, which will give you the equivalent pressure in inches of water column.
Here’s an example: Let’s convert 5 PSI to WC. The calculation would look like this:
5 PSI 27.708 = 138.54 inches WC
The conversion factor
The key to these conversions is the number 27.708. If you see slightly different numbers in use (like 27.7076), that’s generally because someone has rounded off the number at a different decimal place.
Practical Applications and Considerations
Inches of water column (WC) and pounds per square inch (PSI) are used in different situations. You’ll often see WC measurements on residential gas appliances. PSI is more common in commercial and industrial settings where higher pressures are needed.
No matter where you’re measuring pressure, accuracy is essential. Correct measurements keep equipment running efficiently and safely.
While the formulas we’ve discussed are very precise, conversion charts can also be helpful. These charts offer quick references. Use a chart to double-check your calculations from the formula.
Finally, be sure you’re using the correct units! Make sure your starting measurement is really in inches of water column and not some other pressure unit.
In Conclusion
Water column (WC) and pounds per square inch (PSI) are two different ways to measure pressure. If you know the WC, you can calculate the PSI, and vice versa.
Understanding how to convert between these two units is essential for anyone who works with pressure systems, from plumbers to HVAC technicians, to engineers.