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The #1 Reason No-Hub Piping Systems Fail: Hydraulic Jump


Excluding fitting restraints poses a credible risk for your projects. Pipe failure can happen for many reasons, including the all-too-common hydraulic jump failure.

Builders often rely on field methods to create a soil pipe system, which can seem like a cost and time-saving tactic at the moment. However, these ad hoc solutions are not reliable enough to be trusted in situations where pipe integrity is vital, such as when a hydraulic jump occurs.

What is a Hydraulic Jump?

Primarily, a hydraulic jump occurs when liquid traveling at high velocity discharges into an area with lower velocity. The collision of these liquids creates a sudden rise in the liquid surface.

In the case of rainwater leader systems carrying water in a high-rise building, for instance, water travels down the circumference of the pipe or outer walls. Often, a hydraulic jump occurs when this fast-moving water must change direction from a downward vertical angle to a horizontal pipe at a system’s base.

At the base of the stack, this column of water with an air slug up the middle collapses as it changes directions and slows dramatically. However, the water coming down behind is traveling much faster. When the collision of these two travel speeds occurs, this is considered a hydraulic jump.

When a great deal of sudden pressure is forced through a pipe system, pipe failure or separation is a real risk. Choked liquid flow is a common but relatively mild result, for example.

However, a hydraulic jump can also be the cause of catastrophic failure, as well, such as when pipes separate. The resulting flooding can bring havoc to a building site or an established rainwater leader system even years later.

How Typical is a Hydraulic Jump?

A hydraulic jump is the overall #1 cause of pipe and fitting joint failure. It’s hard to say how many pipe failures occur due to hydraulic jump, but the issue is significant enough that builders and plumbing industry professionals seek out remedies regularly.

Sometimes, a hydraulic jump creates an issue so severe that the resulting damage makes the news. This was the case when the UPHS Translational Research Center in Philadelphia experienced a pipe separation event that created major havoc and damage. Interestingly, engineers who studied this event concluded that only 82 pounds of thrust on the 12 in. rain leader system installed there was enough to cause pipe separation.

Sufficient testing might have foreshadowed this unfortunate occurrence, but it is essential to consider the limitations of every rain leader system. In the case of the medical facility, the 1200 square foot roof collected so much water during an unexpected, extreme rain event that the hydraulic jump was significant enough to lead to pipe separation.

What You Need to Know to Protect Property from Hydraulic Jump Events

Prevention is by far the most effective way to protect your property and build sites from damage created by hydraulic jump events.

You can help prevent pipe separation occurrences by considering several precautions:

  • Construct rainwater leader systems that account for significantly steep drainage needs to reduce the downward velocity
  • Use quality no-hub fitting restraints at critical joints
  • Employ the services of a qualified engineer who can calculate the ideal thrust at any given point in your system

How Do Engineered Fitting Restraints Mitigate the Risks of a Hydraulic Jump?


Although the International Plumbing Code has specified the use of fitting restraints for cast iron soil pipes greater than four inches since 2009, untested field-devised solutions are still being used.

Field-created methods used to create restraints might seem like an attractive option for project managers and site engineers who are trying to save money and make use of readily-available materials. However, these alternative methods not only create more risk for the project in the near and far future, but they are also actually more costly than investing in quality, engineered restraints such as those offered by HoldRite.

Our #117 Series No-Hub Fitting Restraints have been engineered to reliably restrain pipe and fittings for up to 50 feet of head pressure, which exceeds the 10-feet minimum specified in the Code. HoldRite no-hub fitting restraints give our clients peace-of-mind, knowing they have used industry-trusted components to secure their pipe systems.

You may be surprised to discover that an investment in engineered no-hub fitting restraints versus relying on a makeshift, field-created solutions can help increase your bottom line by reducing labor and material costs.

HoldRite’s #117 Series Offers Several Notable Benefits:

  • Water blow-out protection in rain leader systems
  • Supporting joints from both longitudinal movement separation and diagonal misalignment
  • Quality construction using materials like stainless steel, black iron, and rust-resistant, zinc-galvanized components
  • Hydraulic jump protection at changes of direction along joints
  • Easy installation requiring no special tools

Your installation team will be able to install our no-hub fitting restraints in a fraction of the time makeshift methods are taking you. Each restraint takes only minutes to install, a time saving that quickly adds up across your project.

With HoldRite, you don’t have to supplement with parts or tools from other sources. Each of our kits includes everything your installers will need, including the significant number of straps and clamps.

Not sure which products are right for you? Contact us by phone or email, and we’ll connect you with a knowledgeable client service representative who can guide you through the ordering process or set you up for an always-free estimate.

HoldRite Converts Makeshift Methods into Engineered Solutions

Our three decades of experience in the industry inform the way we approach our manufacturing process, start to finish. We’ve evolved from a single-product family business into an industry-leading international manufacturer because we understand the issues facing the industry. We’ve provided hundreds of millions of products used in projects big and small for projects in every sector.

HoldRite prides itself on creating engineered solutions that add professionalism, improved quality, stronger craftsmanship, and smart innovation. We work diligently to transform your processes so you can keep transforming the world.

View our many HoldRite product catalogs and brochures to find the right plumbing support solutions for you.