Aqua-Hot 400D / 450D Heating System Parts and Service

If you're maintaining or repairing your Aqua-Hot 400D or 450D hydronic heating system, finding the right parts and performing regular service is essential for long-term performance.
This guide covers key replacement parts, maintenance kits, and where to buy genuine components online.

🔧 Replacement Parts & Annual Service Kits

Routine annual service helps keep your Aqua-Hot system efficient, quiet, and reliable. Aqua-Hot’s 400D and 450D service kits typically include:

• Fuel Filter (FLE-120-100)

• Diesel Nozzle (WPX-886-41A)

• Electrode Adjustment Tool (WPX-310-646)

• Burner Gasket (HDE-700-205)

• Portable Refractometer (MSX-907-162)

• General Fuel Filter Kit

These kits are designed specifically for your Aqua-Hot model and are available from authorized dealers and online retailers.

For genuine replacement parts, browse Aqua-Hot Parts and Accessories at Hydronic Heating Warehouse — your trusted source for Aqua-Hot nozzles, filters, gaskets, sensors, and electrical components.

🛠️ Maintenance & Service Resources

For detailed service information and official documentation, visit the Aqua-Hot Library.
It includes downloadable service manuals, use & care guides, and technical bulletins for all major models — including the 400D, 450D, 600D, and 675D.

You’ll find:

• Maintenance procedures and annual service instructions

• Wiring and plumbing diagrams

• Parts lists with OEM numbers

• Troubleshooting and repair information

Additional resources:

• HeatMyRV Maintenance Guides: Step-by-step walkthroughs for performing annual service on Aqua-Hot 400D, 450D, and related models.

• ManualsLib: An alternate source for downloadable Aqua-Hot service manuals.

• Tiffin Motorhomes Knowledge Base: Instructions for Aqua-Hot 450DE wiring, installation, and service.

🔄 Factory Remanufactured Units

If your Aqua-Hot unit requires major repair or replacement, the manufacturer offers factory remanufactured systems that include:

• New burn chamber for low emissions

• New boiler tank and cabinet with serialized ID

• Factory inspection, testing, and certification

• 1-year limited warranty

To confirm eligibility, contact Hydronic Sales at 866-895-4556.

🛒 Where to Buy Aqua-Hot Parts & Kits Online

⚙️ Pro Tips for Aqua-Hot Maintenance

1. Service Annually: Replace the fuel filter and nozzle once a year or every 500 hours.

2. Use Correct Antifreeze: Match the color (green or pink) and verify mixture with a refractometer.

3. Inspect Electrodes: Proper electrode gap ensures clean combustion and ignition.

4. Check for Leaks: Look for coolant seepage or diesel odor — early detection prevents costly repairs.

5. Keep Records: Track service dates and part numbers for future reference.

✅ Final Thoughts

A properly maintained Aqua-Hot 400D or 450D provides years of reliable heating and hot water.
Whether you’re performing annual maintenance, troubleshooting a burner issue, or sourcing new parts, using genuine components is key.

For OEM parts, manuals, and service resources, visit:

• Hydronic Heating Warehouse – Aqua-Hot Parts

• Aqua-Hot Library – Official Manuals & Documentation