The choice must take into consideration the craftsmanship of the installation, convenience, and coordination among the trades.
by David Dexter, FNSPE, FASPE, CPD, CPI, LEED BD+C, PE
When I first got into the plumbing trade it was very common to lay out and install piping sleeves before the walls or floors were poured. A skilled tradesperson needed to be accurate and place the sleeves in the precise location to ensure that they were located as the system layout dictated, were within the wall space, and would not interfere with the work of the other trades.
However, over the years, many contractors and skilled trades personnel have forgotten how to accomplish this effort, or maybe they decided that sleeves were not necessary and utilized other means to penetrate the wall or floor structure. But is this an improvement in the quality and value of the facility or just a means to reduce cost without improvement? Has the skill of the tradesperson been reduced in such a way that locating sleeves is problematic?
Sleeves vs. Core Drilling
A sleeve, according to the ASPE Plumbineering Dictionary, is a hollow, cylindrical tube that surrounds a pipe for penetration. Or, as the term is most commonly used in construction, a sleeve provides a means of access through a material for a pipe, conduit, wiring, etc. The plumbing designer needs to coordinate with the structural engineer, electrical, mechanical, and plumbing subs, as well as the site work subs, to ensure that sleeves are placed in the proper location for the installation of whatever will be inserted into them after the concrete or assembly is placed.
A sleeve is normally larger than the item being inserted through it. For example, a 2-inch pipe would probably have a 3-inch sleeve. You also must consider the OD (outside diameter) of the material passing through the sleeve; a 2-inch water pipe with 1-inch insulation would need a sleeve with a minimum ID (inside diameter) of 4 inches. On larger projects, where multiple sleeves might be involved, a sleeve schedule could be provided. A sleeve schedule would specify the size required to accommodate a certain size pipe as well as the acceptable material for the sleeve. In instances where a fire-rated penetration is required, the sleeve must be appropriately sized to accommodate the carrier pipe, any insulation or exterior coating of that pipe, and the fire stop material.
Sleeves typically are provided with a water stop ring or support rods to “lock” the sleeve into the concrete floor or wall. Water stop rings are used where the penetration is subject to water incursion between one side of the assembly and the other. In cases where water incursion is not a concern, support stubs or some other means of locking the sleeve in the assembly must be provided.
Sleeves in general allow for a clean termination near the assembly in which they are installed. They provide a “square” and even surface for the escutcheon or trim plate to be affixed. In the case of floor sleeves, they serve a similar function in addition to providing a water stop and support for a vertical carrier pipe; hence, it is important that the floor sleeve be held securely in place and that a water collar is in place to minimize water passage between floors.
As noted earlier, over the years (I will not state how many) skilled trade professionals, contractors, and even consulting engineering professionals have moved away from sleeves. Today, many chose to core drill through the structure to provide for passage of the carrier pipe. Depending on the reason for the penetration and what is passing through that opening, the size of the core will need to accommodate and address several concerns: the size of the carrier pipe, the thickness of the pipe insulation (if insulated), the thickness of any seal used to close the annular space, sealing against water penetration, fire-rating as necessary, etc. Additionally, core drilling can cut through rebar or other structural components, so close coordination with other trades must be considered.
Whichever method is used, however, they both provide the same path for pipe routing.
If the penetration is through an assembly that must be watertight, then the penetration must be sized to accommodate a means to seal the annular space around the carrier pipe. Generally, this will be accomplished using a Link-Seal or similar product. The seal must have sufficient strength to seal the opening while not damaging the carrier pipe, and it must be flexible enough to hold the carrier pipe in place while it tries to move through expansion or contraction.
Sleeves or penetrations are problematic in assemblies that are fire-rated. Such penetrations must be protected by approved and rated assemblies to maintain the rated value of the assembly being penetrated. Regardless of how the penetration is made, sleeve or core drilled, the penetration must be protected by an approved means. Depending on the visibility of the penetration, one must select the means of protection as appropriate for the visibility of the finished assembly.
According to CSI, there are three components to any penetration:
- Barrier: A structural barrier of some type through which a hole is cut to allow a penetrant (such as a pipe or tube) to pass through. Some common examples in the processing environment are walls, ceilings, floors, electrical panels and enclosures, mechanical control panels, and jacketed tanks or vessels.
- Penetrant: The object that runs uninterrupted through the hole in the barrier, from one side to the other. This includes process piping and tubing, electrical conduit, tube-in-tube floor transitions, electrical wire and cable, hydraulic hoses, refrigeration pipe and tubing, structural supports, and plastic drains or vents.
- Sealing device: The element that blocks the open area around the penetrant to seal off one side of the barrier from the other. Examples include temporary seals like putties, sealants, or caulks as well as older, more traditional solutions like metal wall plates and escutcheons or newer technologies such as flexible boots or modular mechanical systems.
The demands of each application vary widely, so sealing solutions vary depending on a number of factors: sealing new piping; sealing around existing piping; sealing around wire, cable, tubing, or hose; fire, pressure, or NEMA rating requirements; openings in walls, ceilings, or floors; openings in thin sheet metal or plastic; seals exposed to cleaning solutions or harsh environments; seals located outdoors where they are exposed to sunlight and temperature extremes; and tube-in-tube floor or wall transitions, just to name a few.
Putties, Sealants, and Caulks
In process piping environments, these options are more of a temporary quick-fix than they are an actual sealing device. Their ability to conform to any shape to fill a void makes them a tempting choice to seal penetration gaps. However, putties, sealants, and caulks merely cover; they do not provide a legitimate seal around the piping surface. Their inability to remain pliable over time, their inability to withstand movement and vibration, and the mess associated with their application also make them a poor choice as a lasting solution in sanitary processing areas.
For many years the traditional solution for covering piping penetrations in walls, floors, and ceilings has been to use stainless steel escutcheon plates, also known as wall plates. They temporarily cover the gap in the opening and provide a decorative trim to the penetration. It is a common and inexpensive solution for covering gaps, but it has proven to be ineffective for most processing facilities. Most escutcheon plates are installed by applying caulk or sealant to the back of the plate and pressing it against the barrier. They typically remain in position for a brief period until, over time, the caulk or sealant inevitably dries out and loses its adhesive qualities. Combined with the movement and vibration of process piping, the plate soon separates from the wall, exposes the gap it was meant to cover, and begins to slide down the piping.
Although escutcheon plates are relatively inexpensive and may be a short-term solution to covering piping penetrations, they do not provide a hygienic, permanent seal between the piping and the wall or ceiling. Their design can’t compensate for piping misalignment, pipe slope, movement, or vibration.
An effective alternative to escutcheon plates is a type of sealing device that incorporates an elastomeric boot to seal around the piping. The flexible boot can be trimmed to size in the field to maintain an air-tight seal around the piping. Unlike a rigid metal escutcheon plate, a flexible design maintains a secure seal around the piping despite pipe slope, misalignment, or movement. The elastomeric boot also dampens piping vibration and absorbs noise.
Installation of flexible boot seals is much easier than escutcheon plates due to a self-sealing base that fastens securely to walls, floors, and ceilings using a pre-drilled stainless steel mounting ring with screws. With this design there is no need for caulks or sealants, and with a mounted base, the boot will not separate from the wall, floor, or ceiling.
Modular Mechanical Seals
This seal design incorporates a series of elastomeric segments or links that are bolted together to form a ring around the penetrant. The ring slides into the opening and, when tightened, expands to fill the gap. Modular mechanical seals are often used to provide a rigid, watertight seal around pipe penetrations in concrete foundations and structural openings where a hygienic seal is not required.
Each mechanical seal must be assembled using elastomeric links, pressure plates, and bolts. Some designs can offer fire-rated or pressure-rated options, but their non-hygienic design precludes them from use in food, dairy, beverage, and pharmaceutical environments without being covered by an external seal designed for sanitary settings.
Once installed, the rigid design holds the piping securely and doesn’t allow movement. This feature is an advantage in some utility, drain, or sewer applications, but it would create stresses in most process piping installations due to thermal expansion and contraction. If not allowed to flex slightly, piping is subject to material fatigue and potential failure in joints and connections.
Pros and Cons of Penetration Methods
As a manner of good workmanship, I have a preference for pre-placed sleeves vs. the overuse of core-drilled penetrations. Each method has its pros and cons, but pre-placement requires more forethought and coordination.
Sleeves allow appropriate coordination with the elements of the building system—walls and structural components of the slabs and walls. They may extend above the floor slab to provide a “water dam” within rooms that are subject to flooding, thus minimizing water leakage to the floor below. As they are embedded within the slab and structural system, they can support the carrier pipe that passes through the sleeve with the aid of a riser clamp. This type of installation is cleaner than coring holes after the fact. It also will allow insulation to pass through with the carrier pipe.
Their layout requires more upfront planning and coordination with the other trades to ensure that everyone is measuring from a common point. This is especially true where a floor slab sleeve must fall within a wall assembly.
Cored Penetration Pros
This method allows for penetrations to be made after the concrete wall or floor has been poured. Penetration locations must be coordinated with the various building elements in-place; however, this may require additional efforts to locate and coordinate with structural elements embedded in the concrete. Less pre-planning and layout are required.
Cored Penetration Pros
Care must be taken to avoid structural elements when coring through structural components such as floor slabs, pan system slabs, and any reinforced concrete component. The penetration should be sized to accommodate a means of sealing the interstitial space between the core wall and the carrier pipe to prevent water or debris from transferring from one side of the penetration to the other. Pipe insulation cannot be continuous through the sleeve if the interstitial space is to be sealed. This approach may add complexity to providing an appropriate firestop assembly.
While either method, pre-placed sleeves or core-drilled penetrations, will accomplish the same end result, in my judgment pre-placed sleeves provide a better installation. The pre-placement shows better workmanship and a higher level of skill than core drilling after the fact. It also works better in areas where watertightness is desirable.
Sleeves should be addressed within the project specifications and detailed within the construction drawings. The level of detail should be such that the contractor would understand that the pre-placed method is preferred. The use of core-drilled penetrations should only be used as a last resort to accommodate design changes in the later stages of the construction process or to address a limited number of penetrations that the contractor missed. Good workmanship and appropriate quality control should ensure that cast in-place, pre-placed sleeves are sufficient for all penetrations.
About the Author
David D. Dexter, FNSPE, FASPE, CPD, CPI, LEED BD+C, PE, is a Registered Professional Engineer, Certified Plumbing Inspector, and Certified Plans Examiner with more than 40 years of experience in the installation and design of plumbing systems. He specializes in plumbing, fire protection, and HVAC design as well as forensics related to mechanical system failures. Dave serves as Chair of ASPE’s Main Design Standards Committee, Chair of the Bylaws Committee, Co-Chair of the College of Fellows Selection Committee, and Co-Chair of the Professional Engineer Working Group. He also was the 2008–2009 President of the Engineering Foundation of Ohio, 2010–2011 President of the Ohio Society of Professional Engineers, and 2012–2014 Central Region Director for the National Society of Professional Engineers.
The opinions expressed in this article are those of the author and not the American Society of Plumbing Engineers.