Water Hammer Arrestor Size Chart: Get It Right the First Time!

Decoding the Water Hammer Arrestor Size Chart: A Step-by-Step Guide

Choosing the right water hammer arrestor size is crucial for preventing noisy and damaging water hammer in your plumbing system. Using a water hammer arrestor size chart correctly will ensure you select the appropriate model for your needs. This guide walks you through the process.

Understanding Water Hammer

Before diving into the chart, let’s clarify what water hammer is and why it’s important to prevent it.

• What it is: Water hammer is the loud banging or hammering noise that occurs when a valve or faucet is quickly shut off. The sudden stoppage of water flow creates a pressure surge.
• Why it matters: These pressure surges can damage pipes, fittings, appliances (like washing machines and dishwashers), and even the water heater. Over time, this can lead to costly repairs and potential water damage.

Introduction to the Water Hammer Arrestor Size Chart

The water hammer arrestor size chart is a lookup table that correlates plumbing fixture units (PFUs), pipe size, and arrestor size. It helps you determine the correct arrestor size based on the specific demands of your plumbing system. Different manufacturers might have slightly different charts, so always refer to the chart provided by the manufacturer of the arrestor you plan to use.

Key Components of a Typical Chart

• Fixture Unit (FU): This represents the demand of a particular fixture. For example, a bathroom sink might have a lower FU value than a washing machine.
• Pipe Size (Nominal): This is the inside diameter of the pipe where the arrestor will be installed (e.g., 1/2 inch, 3/4 inch, 1 inch).
• Arrestor Size: This corresponds to the specific model or classification of the water hammer arrestor (e.g., A, B, C, D). These letters typically represent increasing arrestor capacity.

Finding the Right Arrestor Size: A Practical Guide

Follow these steps to accurately determine the correct arrestor size using a water hammer arrestor size chart.

1. Identify Fixture Unit (FU) Values:

   • Consult a plumbing code book (such as the Uniform Plumbing Code or the International Plumbing Code) or the manufacturer’s specifications for each fixture to determine its FU value.

   • Create a table listing each fixture and its corresponding FU value. For instance:

     Fixture	Fixture Unit (FU) Value
     Bathroom Sink	1.0
     Kitchen Sink	2.0
     Toilet	4.0
     Shower	2.0
     Washing Machine	6.0
     Dishwasher	2.0

2. Calculate the Total Fixture Units:

   • Sum the FU values of all fixtures connected to the pipe segment you’re protecting.
   • For example, if the pipe segment serves a bathroom sink (1 FU), a toilet (4 FU), and a shower (2 FU), the total FU value would be 7.

3. Determine the Pipe Size:

   • Measure the inside diameter of the pipe where the arrestor will be installed. This is typically expressed in nominal pipe size (e.g., 1/2 inch, 3/4 inch, 1 inch).

4. Consult the Water Hammer Arrestor Size Chart:

   • Locate the section of the chart that corresponds to the determined pipe size.
   • Find the range of FU values that includes your calculated total FU value.
   • Identify the corresponding arrestor size (e.g., A, B, C) for that FU range and pipe size.

   • Example Chart Snippet (Illustrative Only – Refer to Manufacturer’s Chart):

     Pipe Size	Fixture Units (FU)	Arrestor Size
     1/2 inch	1-5	A
     1/2 inch	6-10	B
     3/4 inch	11-20	C
     3/4 inch	21-30	D

     Important: This table is a simplified example. Always refer to the manufacturer’s specific size chart.

5. Consider Special Cases:

   • Multiple Fixtures Used Simultaneously: If multiple fixtures are frequently used at the same time (e.g., in a commercial setting), consider increasing the arrestor size.
   • Long Pipe Runs: For long pipe runs, especially in commercial buildings or multi-story homes, it might be necessary to install multiple arrestors along the pipe to effectively dampen water hammer. Consult a plumbing professional in such cases.
   • Washing Machines and Dishwashers: These appliances are notorious for causing water hammer. Install arrestors as close to the appliance as possible.

Important Considerations

• Manufacturer’s Chart: Always use the water hammer arrestor size chart provided by the manufacturer of the arrestor you are using. Charts can vary slightly between manufacturers.
• Professional Advice: If you are unsure about any part of the process, or if you have a complex plumbing system, consult a licensed plumber. They can assess your specific needs and recommend the appropriate arrestor size.
• Installation Location: Install the arrestor as close as possible to the fixture or valve causing the water hammer.
• Air Chamber vs. Arrestor: Air chambers are an outdated and often ineffective solution for water hammer. Modern water hammer arrestors are far more reliable and efficient.
• Maintenance: Water hammer arrestors are generally maintenance-free, but it’s a good idea to inspect them periodically for leaks or damage.

By following these steps and using the correct water hammer arrestor size chart, you can effectively protect your plumbing system from the damaging effects of water hammer.

Alright, hopefully, you’ve got a better grasp of that water hammer arrestor size chart stuff! Go get ’em, and remember, a little planning goes a long way toward saving you some plumbing headaches later!