| Water Service Type | Use galvanized steel only where the applicable plumbing code and project specification permit it. | Threaded steel or malleable-iron fittings; dielectric fittings where dissimilar metals are joined. | Confirm the pipe material is approved for the intended potable or non-potable water application before installation. | Galvanized steel may be unsuitable for some modern potable-water projects because internal corrosion can reduce flow and affect water quality. |
| Pipe Standard | Select pipe manufactured to a recognized specification, such as ASTM A53 for galvanized steel pipe where applicable. | Choose fittings with compatible nominal pipe dimensions and pressure ratings. | Verify markings, nominal size, wall thickness, coating condition, and documentation before cutting or threading. | Do not treat galvanized coating thickness as a substitute for pipe-wall thickness or pressure-rating verification. |
| Nominal Diameter | Size the pipe from the calculated design flow, allowable velocity, available pressure, and system length. | Use reducers, bushings, tees, and elbows with matching nominal pipe size and thread form. | Keep the pipe diameter consistent through long runs where possible to limit friction losses. | Actual inside diameter varies with wall thickness; calculate losses using the applicable internal diameter. |
| Wall Thickness | Choose a wall thickness suitable for operating pressure, temperature, external loads, corrosion allowance, and local code requirements. | Use fittings and valves rated for at least the same system pressure and temperature conditions. | Protect thin or damaged sections from impact, bending, and excessive threading. | Pressure ratings are system-dependent; confirm the rating of every component, not only the pipe. |
| Pipe End Connection | Use factory-threaded or field-threaded ends when a threaded installation is permitted. | Compatible options include threaded elbows, tees, unions, couplings, nipples, valves, and adapters. | Cut square, remove burrs, apply a suitable potable-water thread sealant or tape, and tighten without over-torquing. | Damaged threads or excessive tightening can crack fittings, distort threads, and expose bare steel to corrosion. |
| Thread Compatibility | Use the same approved thread type and nominal size throughout the threaded joint. | Common pipe-threaded systems use tapered pipe threads; adapters may be required when connecting to straight-thread components. | Inspect thread engagement and ensure the joint seals on the intended thread or sealing surface. | Never force different thread standards together. Verify the thread standard and sealing method before assembly. |
| Grooved Connection | Use grooved-end galvanized pipe only with a compatible grooving method and approved coupling system. | Grooved couplings, flexible or rigid housings, gaskets, grooved valves, and grooved fittings. | Cut and groove the pipe to the coupling manufacturer's published dimensions; clean the groove and install the gasket correctly. | Check groove diameter, depth, pipe end condition, gasket compatibility, and bolt torque. |
| Flanged Connection | Use flanges where equipment removal, maintenance access, or larger-diameter connections are required. | Threaded or welded flanges, matching bolts, nuts, washers, and a gasket suitable for the water service. | Align flanges without using bolts to pull misaligned pipe into position; tighten bolts in a diagonal sequence. | Confirm flange dimensions, pressure class, gasket material, bolt grade, and face condition. |
| Transition to Copper or Other Metals | Use a purpose-made transition fitting rather than directly joining incompatible metals. | Dielectric unions, dielectric flanges, insulated nipples, or approved transition adapters where required. | Install the isolation component according to the fitting instructions and prevent metallic bridging through supports or accessories. | Galvanic corrosion can occur when galvanized steel is directly connected to certain dissimilar metals in an electrolyte. |
| Valves and Equipment | Select valves, meters, strainers, backflow devices, and pumps with compatible connection types and water-service ratings. | Threaded, grooved, or flanged valves and equipment connections matching the selected pipe system. | Provide unions, flanges, or other serviceable connections where equipment may need removal. | Install valves in the correct flow direction and provide access for inspection, testing, and maintenance. |
| Corrosion Protection | Use pipe with an intact zinc coating and avoid unnecessary exposure of bare steel. | Use compatible repair material for small damaged areas and corrosion-resistant supports where specified. | After cutting or threading, clean the area and repair damaged coating in accordance with the project specification. | Do not bury or conceal heavily damaged pipe, wet insulation, or joints showing active corrosion. |
| Buried Installation | Use galvanized steel underground only when permitted and when soil, moisture, and corrosion conditions are acceptable. | Use approved transition fittings, protective sleeves, coatings, or cathodic-protection measures where required by the design. | Provide suitable bedding, avoid sharp rocks, protect joints, and maintain required cover and separation from other utilities. | Soil chemistry, stray currents, and persistent moisture can accelerate external corrosion. |
| Indoor Supports | Use supports and hangers sized for the filled pipe and arranged according to the applicable plumbing or mechanical code. | Use compatible metal or isolated supports that do not damage the zinc coating. | Support horizontal and vertical runs, provide alignment, and allow for inspection and valve operation. | Prevent abrasion, point loading, and trapped water between the pipe and support. |
| Thermal Movement | Account for temperature changes in hot-water, process-water, and exposed installations. | Use expansion loops, flexible connectors, guides, anchors, or movement-rated couplings as designed. | Install anchors and guides at the locations shown on the engineering design; do not restrain movement unintentionally. | Rigid threaded joints can be stressed by movement, vibration, or misalignment. |
| Flushing and Cleaning | Flush the completed system with clean water before commissioning. | Use temporary flush points, drain valves, strainers, and sampling points where required. | Remove cutting debris, thread sealant residue, metal particles, and construction contaminants. | Follow local requirements for disinfection and water-quality testing when the system supplies drinking water. |
| Pressure Testing | Test the complete installed system at the pressure and duration required by the governing code or project specification. | Use calibrated test gauges, test pumps, caps, plugs, and isolation valves rated for the test pressure. | Isolate components that cannot withstand the test pressure and inspect every joint for leakage. | Do not use compressed air for testing unless specifically allowed by the applicable safety requirements. |
| Final Selection Rule | Choose the pipe, fitting, connection, and installation method as one compatible system. | Match material, size, pressure rating, connection type, gasket or sealant, and corrosion-protection method. | Confirm the design, installation, inspection, flushing, and testing requirements before concealment. | The final selection must comply with local plumbing codes, water authority requirements, and the engineer's project specifications. |
