How to Specify Plastic Downspout Nozzles for Commercial Projects: A Contractor & Engineer’s Guide

When a roof-drain leader runs down inside the wall and exits through the facade, something has to finish that opening and throw the water clear of the building. That part is the downspout nozzle; on site you'll hear it called a cow tongue or a lamb's tongue. It sits in Division 22 with the storm drainage piping, and it gets less attention in the spec than it deserves, because it is one of the few drainage components the owner looks at every day.

This guide covers how to specify a plastic nozzle on commercial and multi-family work, using our LokPlate™ plastic downspout nozzle as the basis of design. Every dimension below comes from our published data sheet, Installation & Connection Guide and CSI section.

Start with the leader pipe

The nozzle is sized to the pipe. Hydraulic sizing of the leader belongs in Section 22 14 00, and once that pipe size is set the nozzle follows it. LokPlate comes in seven nominal sizes (2″, 3″, 4″, 6″, 8″, 10″ and 12″) and fits Schedule 40/80 PVC and ABS pipe.

Pipe projection is the detail to get right before the nozzle goes on. The leader has to extend past the finished wall far enough to seat fully in the nozzle's inlet hub, and the recommended projection equals the hub depth:

• 2″ through 6″ nozzles: 1.57″
• 8″ nozzle: 1.97″
• 10″ and 12″ nozzles: 2.50″

Put that dimension on the drawings. A leader cut flush with the finished wall leaves the nozzle nothing to bond to.

Choose the connection for the pipe material

Our Installation & Connection Guide documents four configurations. Name the one that fits the project and delete the others from the spec.

• PVC or ABS pipe is the default. The nozzle solvent-bonds directly to the pipe, with ABS-to-PVC transition cement on PVC and ABS cement on ABS.
• For straight no-hub cast iron, use the Direct-to-Cast-Iron Adapter Kit: a size-matched elastomer adapter plus 3M™ Marine Adhesive Sealant 5200 (or equivalent). The kit covers 3″ through 12″ and is for straight pipe only, never elbows or fittings. Contact us to order it.
• No-hub cast-iron elbows and fittings, no-hub pipe that doesn't project far enough for the kit, and 2″ cast iron use a shielded cast-iron-to-plastic transition coupling onto a Schedule 40 PVC or ABS stub. Select the coupling for the actual pipe materials and outside diameters; the stub then bonds into the nozzle.
• Where the leader ends in male NPT threads, a PVC Schedule 40 spigot × FIPT adapter goes on the threads and its spigot bonds into the nozzle with ABS-to-PVC transition cement.

Material and finish

The nozzle and escutcheon plate are both injection-molded from ASA, a UV-resistant polymer selected for exterior exposure. Color is molded through the part rather than painted on, so there is no coating to chip, peel or touch up, and nothing to rust or corrode. The five standard colors are Black, Oil Rubbed Bronze, Tuscan Bronze, Matte Brass and White. Custom color requests go to our sales team.

For submittals we can provide the resin manufacturer's typical property data for the ASA: impact strength, heat deflection temperature, Vicat softening temperature, density, water absorption and flammability test results.

The wall detail

Metal nozzles are typically fastened to the wall with mounting hardware. LokPlate's patent-pending escutcheon plate locks onto a track molded into the nozzle body instead. No screws, anchors, caulk or glue touch the wall, so the facade is never drilled. The track gives the plate a continuous range of locking positions, which lets it sit flush when the stub runs a little long, short or slightly crooked.

Write one point into the spec explicitly: the plate is a finish piece, not a seal. Seal the wall penetration separately as the contract documents require, and don't use sealant or adhesive to attach the plate to the wall.

Why plastic on a commercial building

Bronze and brass nozzles are stolen for their scrap value. Each theft means a replacement part, a service call and an open pipe in the wall until someone notices. Plastic has no scrap value, which removes the reason to steal it.

Metal also asks for upkeep over the life of the building. Painted finishes fade and flake, and corroding metal leaves streaks down the facade. A molded-color nozzle has no finish to maintain. Clean it with mild detergent and water, and keep solvents off it.

Bird screens

Where birds or rodents are a concern, add the matching LokPlate bird screen. It is size-matched to the nozzle, installs without hardware or solvent, and comes out when the line needs cleaning. On new work it drops into the nozzle before the nozzle is mounted to the pipe. On an installed nozzle it bends and slips in through the front, and the nozzle stays on the wall. Bird screens are sold separately.

The spec section and submittals

Our CSI section 22 14 23, Plastic Downspout Nozzles and Escutcheon Assemblies, is written to drop into a project manual. It names LokPlate as the basis of design with substitutions under Division 01, lists related Sections 22 14 00, 22 14 13 and 07 60 00, and carries specifier notes for trimming the bird screen and connection paragraphs you don't need. It calls for a qualified plumbing or roofing contractor experienced in storm-drainage penetrations. Submittals include:

• The LokPlate product data sheet
• Installation instructions for the connection configuration you selected
• The resin manufacturer's data for the ASA
• The manufacturer's warranty
• Shop drawings of the pipe termination and wall penetration, where the project requires them

The section also calls for one mock-up installation, approved before the rest go in. On a building with dozens of nozzles, that is the cheapest place to catch a projection or sealing problem.

Warranty

LokPlate nozzles and escutcheon plates purchased on or after September 1, 2026 carry our Limited Lifetime Warranty. It covers defects in materials and workmanship for as long as the product stays installed in its original location, and the factory color against excessive fading for 30 years from purchase. Coverage transfers to later owners and needs no registration. It does not cover bird screens, adapter kits or other accessories.

Downloads and support

The data sheet, Installation & Connection Guide, CSI section (an editable Word file) and a Revit family are on our product specifications page. For project-specific questions, a custom color or a cast-iron adapter kit, call (602) 562-4061 or email sales@econocraftmaterials.com.