5 Myths about No-hub Fitting Restraints
There are several misconceptions about no-hub fitting restraints that can affect engineers, contractors, and installers from making confident, well-informed decisions for their projects. Not having the facts could lead to system failures that can cause floods and property damage. To help clear the air, we address a few common myths you may have heard in the field and outline the facts.
Myth: Building codes don’t require no-hub fitting restraints.
Fact: IPC has required restraints for certain cast iron soil pipes for over 10 years.
Back in 2009, IPC stated in Section 308.7.1 that a cast iron soil pipe greater than 4 inches shall be restrained at all changes of pipe diameter greater than two pipe sizes and at all changes of direction with braces, blocks, rodding, or other suitable methods as specified by the coupling manufacturer.
Additionally, it’s always a good idea to check your local codes and stay up to date on the latest regulations and requirements since there’s always something new being added or considered.
Still, plumbing codes are typically viewed as minimum standards. Use other resources, such as model plumbing codes and the U.S. Weather Bureau to better project the potential rainfall in your area so your system is built to handle those specific conditions.
Myth: The specified pipe hangers and supports will do the trick.
Fact: Standard pipe hangers and riser clamps don’t protect fitting joints from separation when experiencing high flow conditions.
Piping systems alone aren’t built to withstand the various conditions they’ll experience throughout the life of the building. Pipe materials and support systems will function properly during normal operation but may not when the system experiences abnormal stress.
Plus, hangers are designed to handle static weight loads, not dynamic longitudinal loads. Pipes can also experience diagonal forces, which, without the proper restraints, can result in fitting misalignment, joint separation and coupling damage or failure.
Read More: The Problem with Field-Devised No-Hub Fitting Restraints
Myth: I did a hydrostatic test, so I don’t have to worry about the piping.
Fact: Hydrostatic tests don’t precisely mimic high-thrust conditions.
Hydrostatic tests are meant to test for leakage, not necessarily performance against thrust conditions. Thrust forces encountered during heavy rain fall conditions can be more severe than the typical test.
During a water test, the piping is usually filled slowly with a hose, so the pipe and fitting joints don't experience sudden thrust pressures. Heavy rainfall, by contrast, imposes intermittent and fierce pressure and thrust forces upon the pipe system.
If siphonic roof drain systems are installed, the pipes will also be subjected to a more “full flow” condition than with common style gravity roof drains. This can cause thrust forces imposed at changes of direction to be even more forceful than piping that experiences lower flow capacities, posing serious failure potentials for no-hub piping system joints.
Myth: Restraints take too much time to install.
Fact: Engineered restraints install in minutes.
Not all restraints take excessive time to install. That’s usually only the case with a field-devised system. Measuring, cutting and bending all the parts to cobble together a restraint that may or may not hold up is not only structurally risky, but it can also take anywhere from 30 minutes to an hour or more each time you need to make one.
In contrast, the HoldRite engineered no-hub fitting restraints, the #117 Series, install in three minutes and don't require field bending, measuring, cutting or modifications. Each kit comes with all the installation components, too, and you don’t need any special tools to install it. You don’t have to worry about the restraint’s reliability either: It’s designed to meet plumbing codes, pipe manufacturers’ installation instructions and the guidelines provided within the Cast Iron Soil Pipe Institute installation handbook.
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Myth: Restraints cost too much.
Fact: Contractors actually save money with engineered restraints.
Contractors can save 30-50% in total installed costs with engineered restraints. Plus, avoiding an upfront cost could end up costing you far more in the future if the pipe separates from the fitting. Joint failures can flood buildings, damage equipment and cause significant job delays, leading to lawsuits and property damage. This is much more costly than installing a reliable restraint system from the start.