Delving into drains

Installing retrofit roof drains can help you increase sales and add value to your jobs

  • A mechanical seal provides a watertight connection to the existing drain leader.
                The seal expands as it is tightened in place and exceeds the ANSI/SPRI RD-1 standard
                of holding a 10-foot column of water without leaking for 24 hours.Photo courtesy of OMG Roofing Products, Agawam, Mass.
  • In place of a traditional clamping ring, a TPO target sheet is hot-air welded to
                a TPO coated flange as one of the final steps to a retrofit roof drain installation.Photo courtesy of OMG Roofing Products, Agawam, Mass.
  • Wire brushing an old cast-iron strainer is one of the many steps of the reworking
                    process.Photo courtesy of OMG Roofing Products, Agawam, Mass.
  • This image shows the typical components of a retrofit roof drain, which include
                a strainer, clamping ring, flange studs, drain flange, drain stem and mechanical
                seal.Photo courtesy of OMG Roofing Products, Agawam, Mass.
  • Depending on the application, a scupper-style retrofit roof drain is just one of
                the options available to commercial roofing contractors.Photo courtesy of OMG Roofing Products, Agawam, Mass.

After nearly 25 years on the market, retrofit or insert roof drains remain one of the roofing industry's best-kept secrets. In fact, a recent study conducted by OMG Roofing Products, Agawam, Mass., revealed among commercial roofing contractors, less than 20 percent of respondents said they use retrofit drains on reroofing projects "most" or "all of the time."

This is not surprising: Many consider drains as part of a building's plumbing system and, therefore, not part of the roof system package. However, the reality is roof drains offer an opportunity for you to increase sales and profits while providing value-added services to building owners.

The three options

When it comes to rooftop drains, you typically have three options: you can subcontract the work to a plumbing contractor, rework existing drains or install insert drains. As with everything in the commercial roofing industry, no one strategy is better than the others; they all are appropriate at one time or another depending on several factors.

Subcontracting the drain work to a commercial plumbing contractor can be time-consuming and expensive. Frequently, and particularly when there are many drains on a roof, a plumbing contractor will charge a flat rate for the drain work, which can be as much as $1,500 per drain, and can take up to two hours per drain for installation.

But beyond the costs, scheduling can be problematic. All too often, your time frame and a plumbing contractor's time frame will not be in sync. In addition, there may be increased liability, and plumbing contractors must also gain access to buildings' interiors. The end result is a slower, more expensive, more disruptive process that you'll have to accommodate.

However, there are times when hiring a plumbing contractor is necessary. Such cases include when a specifier insists on installing new drains; extremely complicated change-outs where some or all of the piping also needs to be replaced; or when the union requires a plumbing contractor to do the work.

By far, the most common approach is to rework the existing drain. To complete such a project, you will need a wide assortment of tools, such as a pick ax, hammer, wire brush, chisel, penetrating oil, cleaning solvent, drill, drill bits, replacement hardware (bolts and nuts), gloves, rags and spray paint. Although some rework can be finished in the shop, much of it must be completed on the roof.

Depending on the drain condition, for estimating purposes the average for time and labor is two hours per drain. The first step in the rework process involves removing the strainer dome and clamping ring. More often than not, the strainer dome and clamping ring will be heavily rusted and brittle, and breaking either piece means a trip to the plumbing supply store to purchase replacement parts or a "universal" part if the particular model is obsolete. Either way, you are adding labor and material cost to the project.

Assuming the strainer dome and clamping ring can be removed in one piece, the bolts most likely will need to be cut out and bolt holes re-tapped. Typically, the strainer dome and clamping ring will have to be thoroughly scraped, cleaned, primed and painted for later use.

Once the strainer dome and clamp ring are finished, you can work on the drain bowl. Because drain bowls are seldom removed, this process is almost always performed on the roof. After scraping and cleaning the bowl as best you can, it's always a good idea to carefully inspect it for cracks. Drain bowl cracks are not only a source of roof leaks but also can be difficult to find—an entirely other cost issue. To finish the project, you will likely have to tap new flange studs, prime and repaint the bowl, and reassemble the drain with new hardware.

Although reworking drains can be time-consuming and expensive, there are times when it makes sense to take this approach, such as when a drain is relatively new and not caked with rust and old asphalt. You are not likely to see drains in good condition on roof systems that are 10 years old or older unless they already have been replaced.

Insert or retrofit roof drains are the third option. Retrofit roof drains are designed to slip over existing drain bowls and into drain pipes or leaders, connecting a foot or so below the level of the roof. Such drains typically provide a wide flange to which the roof membrane is secured using virtually any type of roof covering.

Retrofit roof drain designs have come a long way since the 1980s when they were mostly shop-made products. Current retrofit roof drains are precision-engineered for maximum performance and factory-fabricated in quality controlled environments. Drains typically consist of a flange, with or without a depressed sump area, and a stem. The stem is either welded to the flange or the entire body is spun aluminum without any seams. Most retrofit drains also feature a heavy-duty aluminum clamping ring under which the roof covering material is secured, as well as a heavy-duty strainer dome that will not rust.

Drain choices

Insert drains are available in different sizes, shapes and styles for every application and preference. Currently, there are plastic, copper and aluminum drains on the market as well as those with and without a mechanical seal and those with coated or primed flanges for attaching thermoplastic, polymer-modified bitumen and even spray polyurethane foam roof coverings. In addition, there are retrofit scupper drains, gutter drains, new connection drains and even tamper-proof drains. Some firms also will customize drains for specific rooftop applications. The bottom line is there's a retrofit drain solution for every application.

Many drains will weather better than uncoated cast iron, and most are available with traditional clamping rings or membrane-specific coatings or materials for a better watertight connection at the roof level. Regardless of its material, the most important aspect of a retrofit drain is its ability to quickly remove water from the roof and to remain watertight even if the drain line backs up and floods the roof.

The critical issue is to use a retrofit drain with a mechanical seal that securely connects to the inside drain leader. During the 1980s, many insert drains did not include a mechanical seal and were installed using rags, cotton mop strands, mastics or other materials to fill the gap between the outside of the drain stem and inside of the building's existing leader. Without a proper mechanical seal, severe rainstorms can back up drain leaders, exposing a building and roof system to potential flood and water damage.

The first mechanical seal was introduced to the market during the mid-1980s. This seal—still in use—features a plastic collar designed to fit into the end of the drain stem. As the seal is tightened in place, a rubber gasket is compressed, securely conforming to the inside of the existing drain leader and providing a watertight seal.


National plumbing codes have long been established for general roof drains; however, currently, there are no code provisions addressing retrofit drains. Historically, when it came to reroofing applications just about anything could and was used to "sleeve" the roof drain, which frequently led to problems.

That concept was the driving force in the early 2000s for SPRI to establish and publish the first standard for retrofit roof drains, SPRI RD-1, which was subsequently approved as a national standard by the American National Standards Institute (ANSI) in 2004. The ANSI/SPRI RD-1, "Performance Standard for Retrofit Roof Drains," test protocol is designed to test a retrofit drain's ability to provide a leak-free connection to existing piping and also includes methods for calculating sufficient drainage capacities.

To meet the standard, a backflow seal "shall withstand a continuous test pressure under the equivalent of 10 foot head of water or 4.33 lbf/in2 (30 kPa) above the elevation of the backflow seal without any visible leakage after 24 hours" (tested in accordance with RF-1 laboratory test method). The rags, cotton mop strands, mastics or other materials used to make the seal will not handle this level of pressure and could result in a water leak in the building. The standard was reaffirmed in December 2009; a copy of the standard is available on SPRI's website,


When compared with other installation options, retrofit roof drains offer a less expensive installed cost. The total time to properly install an insert drain can vary, but on average it takes 15 to 30 minutes. Based on a relatively low cost versus a new drain and rapid installation time, an insert drain's total installation cost is highly competitive.

More important, insert drain installation is completed entirely on the roof by one laborer. Because there's nothing to plumb from the deck's underside, it is not necessary to disrupt building occupants during the installation process.

By contrast, a plumbing contractor installing a new drain needs access to space under the roof deck to work on the drain's underside. In many cases, this disrupts building occupants by having to move ceiling tiles, computers, furniture and people, as well as having to cover floors, walls and equipment to protect them from potential water damage.

Moreover, you will have better control over the entire project schedule without having to rely on a subcontractor for the plumbing work.

When compared with reworking drains, installing retrofit drains also is easier for you to estimate at the outset. After installing a few retrofit drains, you will have a good handle on the actual time it takes to install these units, as well as the costs of the drains and any additional work such as building a sump or installing crickets. Armed with this information, you will be able to estimate the project more accurately than guessing the actual amount of time it will take to clean, paint and repair an existing drain.

Finally, be aware of local codes that pertain to rooftop plumbing to ensure you remain in compliance. Insert drains differ from new drains in that they always are installed into an existing drain, which means roof drainage capacities always should be verified to ensure sufficient drainage. More important, you want to make sure the capacities of the existing drains were sufficient in the first place. If not, appropriate measures, such as installing additional drains, may be required.

Free and clear

Although having sufficient roof drainage is critically important, it's all moot if the drains are not kept free of pine needles, leaves and other debris that can choke the drain's performance. It's no secret ponding water not only can weaken a roof system's integrity but also may encourage vegetation and micro-organism growth on the roof.

A regular roof system inspection and maintenance program will help extend roof system life and may help avoid catastrophic roof system failure. Preventative maintenance programs offer you a way to sell value-added services and keep minor issues from becoming major undertakings. Equally important, roofing contractors understand roof systems, their limits, and how and where to look for potential problems. Building owners and facility managers who are not roofing professionals can inadvertently damage a roof while conducting an inspection.

The drain opportunity

All too often during reroofing projects, drains are a missed opportunity for roofing contractors. Not only can they be a source of additional sales, profits and improved productivity but they also add an attractive aesthetic component, something most building owners will appreciate.

Moreover, drain installation is only the beginning. Drain maintenance also may be an opportunity to provide ongoing value-added services to building owners.

Dan Genovese is a product manager for OMG Roofing Products, Agawam, Mass.


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