With the notable exceptions of earthquakes and landslides, we tend to think of the earth beneath us as stable and immobile.
Plumbing contractors know better. The ground settles and shifts in response to traffic overhead, moisture content in the soil, freeze and thaw cycles and more. That can cause problems with underground pipes, which are subject to pressure from the moving earth.
This is where swing joints are necessary. A swing joint is a pipe joint designed with a series of two to five 90-degree elbows and nipples so that the parts joined are movable and can be rotated relative to the other. That provides some “give” in the connection and can prevent leaks and breaks caused by shifting soil.
Pressing swing joints
The subject of swing joints came up in a recent Viega TechTalk LIVE stream with trainers/master plumbers Bo DeAngelo and Troy Locke. They dealt with a misperception that specific approval is needed for swing joints. Not true. The only requirement is that the joint be made of approved material and that the joining method also be approved. Pressing, like threading, is an approved joining method.
However, that doesn’t mean all joining methods are equal. Pressing is superior to threading for swing joints because it allows for shifting without loosening. The inner components on a Viega MegaPress fitting never rotate; any rotation caused by shifting ground or other external force occurs within the outer casing of the fitting around the inner components.
With threaded pipe, rotation will cause one joint to tighten while simultaneously loosening the joint at the other end of the pipe, potentially causing a leak. MegaPress fittings retain their strength because the pressing force and gripping force remain constant and movement does not create a loosening effect on the joint.
That’s the same reason MegaPress is better for swing joints to compensate for expansion on long runs underground.
The TechTalk LIVE stream concluded with Bo demonstrating the strength of MegaPress fittings and a reminder that Viega ProPress Copper, ProPress Stainless and MegaPress fittings meet the requirements for Special Seismic Certification by seismic testing according to the California Building Code Section 1705.12 and the International Building Code Section 1705.12 for nonstructural components.
TechTalk LIVE is the last Wednesday of every month at 6 p.m. Central Standard Time. Catch the next episode live on March 31.