You will need to calculate the flow rate to help you choose the correct size valve for your application. Check out the DTV FLOW CALCULATOR for assistance.

Insert roof drains are the third option. Insert roof drains are designed to slip over existing drain bowls and into drainpipes or leaders, connecting 10- to 12-inches 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.

Types ofroof drains

But beyond the cost, scheduling can be problematic. All too often, the roofing schedule and the plumber’s schedule are not in sync. In addition, there may be an increased liability, and plumbing contractors must also gain access to buildings’ interiors. The end result can be a slower, more expensive, and more disruptive process that you’ll have to accommodate.

Insert 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.

Moreover, drain installation is only the beginning. Drain maintenance also may be an opportunity to provide ongoing value-added services to building owners. Learn more about OMG’s retrofit roof drain options.

Roof drainsfor flat roofs

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 can also add an attractive aesthetic component, something most building owners will appreciate.

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 or retrofit roof drains. As with everything in the commercial roofing industry, no single option is ‘always’ better than the others; they all are appropriate at one time or another depending on several factors.

The DTV tempering valve is installed into the drain line such that the hot effluent passes over the thermal actuator of the DTV, which controls the cold water inlet port. If the hot effluent is above the specified set-point of the valve, the DTV opens to allow cold water injection. As the hot effluent cools, the DTV automatically modulates to reduce the cold-water inlet flow. At 10°F below the full open temperature, the cold-water inlet is fully closed to conserve water.

By far, the most common approach for many roofing contractors is to rework the existing drains. To complete such a project, you will need a wide assortment of tools, such as a pickax, 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.

This is not surprising: Many consider drains to be part of the building’s plumbing system, and therefore, not part of the roof system package. However, the reality is that roof drains offer an opportunity for contractors to increase sales and profits while providing value-added services to building owners. With that, there are a few retrofit roof drain options to help you achieve that reality.

Most insert 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. Options also exist for TPO- or PVC-coated flanges so that the membrane can be directly heat-welded to the flange thereby eliminating the need for a clamping ring.

ZurnRoof Drains

For DTV installations, most local plumbing codes will require the installation of a check valve or backflow preventer to isolate the drain line from the potable water. A water hammer arrestor must be installed between the DTV and the check valve/backflow preventer if a check valve or backflow preventer is used. Failure to do so may cause permanent damage to the DTV and void the warranty. ThermOmegaTech offers an optional water hammer arrestor and backflow preventers to make life easier. Contact us or your local representative for more information on these products.

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. Drains that are 10 years old or older are not likely to be in great condition.

4"roof drains

Based on the above steps, it’s easy to see why contractors should estimate at least two hours of time and labor per drain, depending on the age and condition of the drains being replaced.

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 as 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. This process, especially tapping new studs, requires a learned skill that is rare to find today.

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.

Commercialroof drains

Drain water from commercial equipment exceeding 140°F (60°C) can be costly – leading to failed inspections, fines, business interruptions, or injury and damage to personnel and equipment.

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.

The DTV is used in applications where a high-temperature discharge flow from commercial equipment must be tempered with cold water before entering a public drain or sewer system. Applications include humidifier discharge to sewer or drain, commercial dishwashers or ware washers, boiler blowdown drain lines, and autoclave discharge.

Roof drainswith Overflow

ThermOmegaTech’s Drain Tempering Valve (DTV) tempers excessively hot drain water to comply with international plumbing code temperature regulations. Thermostatic and completely self-operating, the DTV is plug-and-play, giving you one less thing to worry about.

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 costs to the project.

Since the DTV is open only when the effluent exceeds the specified set-point temperature, it conserves water by automatically turning off cold water when not needed. Available in ½”, ¾”, and 1” sizes in brass or stainless steel, the DTV provides a convenient, economical, and easy-to-use method of tempering hot effluent flows.

In addition, many of the most popular retrofit roof drains today have built-in vortex breakers that improve water flow and help to get water, and excessive weight, off the roof as quickly as possible. In addition, some meet the UPC and IPC code and provide performance data for various water ‘head’ levels.

However, there are times when hiring a plumbing contractor is necessary. Such cases include when a specifier insists on installing new construction vs. retrofit roof 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.