US Assembling an Oversized Radiator

Assembling Your Cast Iron Radiator

(For Hydronic Heating Systems)

Our cast iron radiators can be built to virtually any length you need. For radiators longer than 4 feet (1.2 meters), you have two delivery options:

  • Pay a surcharge for an oversized pallet, or

  • Receive your radiator in multiple sections for simple on-site assembly.

These instructions apply only to radiators installed on closed-loop hydronic heating systems (water-based heating). Steam radiators require different assembly and installation steps—please contact us for separate instructions if you’re working with steam.

Assembly tool, joining threads and gaskets.Each hydronic radiator will arrive in clearly labeled sections (A, B, C, etc.) in the correct assembly order. With your shipment, you’ll also receive:

  • A radiator assembly tool

  • Joining threads

  • Gaskets

Step 1: Prepare the Area

Select a flat, level surface with plenty of working space. Protect your flooring by laying down a sheet or covering. Place two wooden battens (or lengths of timber) on the floor to support the radiator sections—this prevents scratches and makes alignment easier.

Note: All radiators are pressure-tested with air and water before shipping, so some internal moisture may still be present and could drip during assembly.

Step 2: Check Alignment and Thread Direction

Lay out the radiator sections in order. Insert a joining thread into one side of the joint—just a quarter turn to start. Do not force it. One side is left-hand threaded, the other right-hand. The thread should engage smoothly.

For radiators with more than two sections, be especially careful with middle blocks (for example, section B in an A–B–C setup). There is only one correct orientation because of the threading pattern. Test lightly before committing.

Step 3: Fit the Gasket

Slide a clean, dry gasket onto the center of the joining thread. Do not use grease, oil, or sealing compounds.

If a gasket is missing or damaged, call us right away at 212-814-6888 and we’ll send a replacement.

 

 

Step 4: Install the Lower Thread

 

 

Repeat the process with the lower joining thread, inserting it gently until it holds in place.

 

 

 

 

Step 5: Align the Sections

 

Bring the two radiator sections together so they sit flush. Ensure both joining threads are properly aligned with their recesses, and double-check that your gaskets remain centered.

 

Step 6: Use the Assembly Tool

Insert the assembly tool through the section to reach the joining thread. Turn it clockwise until it engages.

Tighten gradually—first give the top thread a partial turn, then switch to the bottom thread, alternating until both are firmly hand-tight. This prevents cross-threading, jamming, or breakage.

Step 7: Final Tightening with a Wrench

Once both threads are secure, attach an adjustable wrench to the assembly tool and give each thread an additional quarter turn.

⚠️ Do not overtighten—this can damage the gaskets or threads.

If you’re using EPDM gaskets, a slight bulge at the joint indicates the seal is correct.

 

Important Reminder

These assembly steps are for hydronic radiators only. If your heating system uses steam, please request our steam radiator assembly and installation instructions before proceeding.

Need Help?

If you have any questions during assembly, call our team at 212-814-6888. We’ll be happy to walk you through the process.