Pressure and flow figures can look like straightforward product-comparison numbers, but they measure different aspects of performance. A working-pressure rating tells you what a particular model is designed to withstand during service. Flow describes the volume of water moving through the hydrant, and the amount available in the field also depends on the surrounding water system and operating conditions. 

If you are comparing hydrants for sale, reading one number in isolation can give you an incomplete picture of the product. We carry Kennedy Valve products and provide Guardian submittal information for project review. In today’s post, we look at what these specifications mean and why they need to be checked against the project requirements. 

What does hydrant pressure rating mean?

A pressure rating tells you how much water the system can deliver through the hydrant. It does not tell you how many gallons per minute the water system will deliver through that unit.

Start with working pressure

Working pressure refers to the pressure the equipment is designed to handle during normal service. The selected rating should be appropriate for the system’s expected operating pressure.

Working pressure vs. test pressure

Test pressure is different. Manufacturers use higher test pressures to verify the assembly’s integrity under specified test conditions. That number should not be treated as the normal operating pressure for the installed system.

Kennedy currently rates its K81A and K81D Guardian models for 250 psi working pressure under AWWA requirements and tests them hydrostatically at pressures up to 500 psi. The K81D is also UL listed and FM approved, so those approvals should also be checked against the project specifications.

Why the model still matters

Knowing which model suits which application helps narrow down the specifications that need to be compared. Pressure ratings need to be reviewed alongside the model’s approvals and configuration.

Flow tells you something different

Flow measures the volume of water moving through the equipment over a period of time, typically expressed in gallons per minute (GPM). A model with a high working-pressure rating does not automatically deliver a particular flow rate. Available flow depends on the water supply, system conditions, outlet configuration, and pressure losses as water moves through the assembly.

Friction loss & outlet configuration

Water loses some pressure as it moves through internal passages and exits through an outlet. Kennedy publishes friction-loss information for the 5¼-inch K81 line across different nozzle sizes and flow conditions. Those published curves show how pressure and flow change under different operating conditions. Outlet selection can change the performance characteristics being reviewed.

Long-term service considerations

Future service matters too, so understanding routine maintenance for Kennedy equipment can help when comparing options for long-term use. The original specification and future service requirements both deserve attention before a product is selected.

System pressure is not the product rating

The pressure available in the water main is a characteristic of the distribution system. The rated working pressure is a specification of the hydrant itself.

Static & residual pressure

Field testing can involve static pressure when water is not flowing and residual pressure while water is being discharged. Those measurements describe conditions within the distribution system. They should not be confused with the hydrant manufacturer’s maximum working-pressure rating.

Match the product to the system

A project therefore needs more than a product with a sufficient working-pressure rating. Connection size, outlet arrangement, system requirements, approvals, and expected operating conditions all need to align.

The water utility fire hydrant specifications can also define details such as valve opening, inlet style, nozzle configuration, and required performance characteristics.

Specifications need to be reviewed as a set

Pressure is important, but it should not be reviewed separately from the rest of the submittal.

Other details to confirm

A purchasing decision can also depend on:

• Required AWWA, UL, or FM status
• Main valve opening size
• Connection and outlet configuration
• Bury or trench depth
• Operating direction and local requirements
• Compatibility with existing infrastructure

Pressure is only one selection factor. The reasons contractors choose Kennedy models also depend on dimensions, approvals, connection options, and other project requirements.

Who offers dependable hydrants for sale near me?

Blair Supply carries Kennedy Valve products for water-main and fire-protection projects, including the Guardian line in our current product offering. We also provide access to product submittal information so you can review the required model and configuration before ordering.

For projects near Highland Park or elsewhere around Rochester, send us the project specifications, required approvals, dimensions, connections, and outlet details. Our team can use that information to help match the project requirements to the appropriate product and prepare your quote. Contact us today to discuss your material requirements!