November 23, 2016

Did you know Duff is the best place to buy commercial roof drains?


It’s true. PVC, ABS and cast iron. No-hub, iron pipe thread, solvent weld. Clamp kit, collars, domes.  Jay R. Smith, Watts, Ancon (now Watts Drainage).

No matter what kind of commercial roof drain you’re looking for, we have the repair parts. Roof drains provide effective internal drainage of water from the roof surface, and are a practical year-round solution to removing water from the surface of roofs in any weather or season.

But the options for repair parts are nearly endless. The first step to finding the right parts is to determine the class of roof drain you’re looking at. “Commercial” roof drains, on the one hand, are often available in a selection of materials including polypropylene, cast iron or cast aluminum strainers, and have large capacities, designed for rooftops as well as ground-level planting areas. “Light commercial” roof drains, on the other hand, are usually characterized by their connection type, either cast iron no-hub or schedule 40 solvent weld.

What replacement parts are available?


The commercial roof drain featured at right, for instance, has an enamel-coated cast iron body, a gravel guard and a dome strainer. It also includes a low-profile dome strainer that twist-locks into the gravel guard. A model like this is available in sizes 3″, 4″, 6″ and 8″ no-hub connections, or as a double sump receiver for 15″ cast iron roof drain. It’s helpful to know not only the connection size and type, but the flange diameter, the overall height (from the very bottom of the entire unit to the top of the slatted cover), and the height of the body (from the very bottom of the unit to the part where the cover actually rests). For measuring tips, keep reading below.

Available repair part kits for this model are the undermount hardware kit; underdeck clamp kit (which includes 4 pieces thread rod, nuts, washers and two clamping bars); sump receiver; adjustable extension assembly kit; 2″ high, external water dam; and a 2″ high, internal water dam.

Moreover, various accessories are available for this particular roof drain, including an adjustable extension kit; cast iron replacement dome; 2″ external water dam; and 24″ x 24″ sump receiver.

02010402010201040205Meanwhile, “light commercial”  roof drains might look like one of the two pictured here. The green one is cast iron with a no-hub connection, and the next one has a PVC hubbed (solvent weld) base that can come with a strainer of varying materials, notably polyethylene (for UV resistance) or cast aluminum.

How and what do I measure?

The first item to measure is the clamp ring–which clamps the drain body and the roofing material securely together. The gravel stop/guard on the ring then prevents roof surface aggregates from being washed into the drain while allowing total drainage through “V” notch weirs. The second item is the drain dome (also sometimes referred to as the basket or strainer).

Measuring the clamp rings

To measure for the clamp rings (sometimes referred to as clamping rings),  it’s ideal to have two measurements. First, read the tape measure from the outside of the rim on one side to the outside of the rim on the opposite side. Most clamp rings have either 3, 4 or 5 bolt holes. This is why it’s helpful to also measure from bolt hole to bolt hole–which measurement should be from the center of one bolt hole to the center of the next bolt hole.

Measuring the clamp ring

Measuring the clamp ring

Measuring the dome

There are two critical measurements for finding the correct replacement dome. First you’ll need to turn it upside down and measure from the outside of the catch edge to the outside of the opposite edge’s catch edge. (See the “B” measurement below, in yellow.) Second, you’ll need to measure the height, which should be taken from the base of the dome to its highest point. (See the “B” measurement below, in red.)

Marathon 12? Poly Dome

Measuring the dome

You name the brand, we have it

The roof drain business has a handful of dominant players that manufacture the units and their replacement parts. We work with these companies on a daily basis. Plus, we have the knowledge and experience to help you determine what parts you need–and can get them to you fast.


Watts Drainage (which aquired the ANCON brand of roof drains); Josam; Wade; Jay R. Smith; MiFab: These are some of the most common companies. Make sure you contact Duff for all your roof drain replacement parts. We’re your one-stop-shop for commercial (and light commercial) roof drains and parts.


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