The Pentair MasterTemp HD ASME Pool Heater 461021 delivers 400,000 BTU of powerful, reliable heating with built-in ASME certification for high-performance applications. Designed to meet rigorous commercial and residential standards, this natural gas heater blends robust construction, efficient heat transfer, and advanced control features to extend your swimming season with consistent warmth.

Featuring a high‑efficiency heat exchanger, electronic ignition, and intuitive digital controls, the MasterTemp HD ASME model provides fast warm‑up times, optimized fuel use, and dependable operation even under demanding conditions. Its ASME‑rated design ensures enhanced safety and durability, making it ideal for larger pools, heavy use, or installations requiring certified compliance.

Pentair MasterTemp HD ASME Pool Heater 461021 Compatibility

• Designed for natural gas pool heating systems.

• Fits 2” plumbing connections common in both residential and commercial pools.

• Compatible with Pentair automation systems including IntelliCenter®, EasyTouch®, and IntelliTouch®.

• Ideal as a replacement for older ASME‑rated or high‑capacity pool heaters.

• Works with standard pool circulation and variable‑speed pump systems.

Key Features

• Supplied under part number 461021 for exact-match ordering.
• BTU rating: 400K BTU.
• Sized by BTU output — match the rating and fuel type to your existing unit.
• Ships from our US warehouse with tracking on dispatch.

Specifications

• Brand: Pentair
• Manufacturer part number: 461021
• Category: Pool Heaters
• Condition: New
• BTU rating: 400K BTU
• UPC / GTIN: 788379858278
• Shipping weight: 149 lb

Frequently Asked Questions

What part number is this pool heater?

This item is supplied under part number 461021. Match that number against your equipment's parts diagram before ordering.

Does the BTU rating have to match my old heater?

The BTU rating should match or exceed your previous heater. Undersizing means the pool never reaches temperature on cold days; oversizing costs more up front but heats faster and cycles less.

Can this run on propane instead of natural gas?

No. Gas pool heaters are built for one fuel and require a manufacturer conversion kit to change. Check the data plate on your existing unit and order the matching fuel type.

What size heater do I need for my pool?

A common rule is 1 BTU per gallon as a minimum, increased for windy sites, uncovered pools, or cold climates. A 20,000 gallon pool typically starts at 250,000 BTU.

Do I need a professional to install a pool heater?

Gas heaters involve gas line sizing, venting and electrical connections, and most jurisdictions require a licensed installer plus a permit. Improper installation voids the manufacturer warranty.

How do I confirm this part fits my equipment?

Check the part number stamped on the component you are replacing, or find it on the parts schematic in your owner's manual. If the number differs or is unreadable, send us your equipment model and serial number and we will verify fitment before you order.

How quickly does this ship?

In-stock items ship from our US warehouse on business days. You will receive tracking by email once the order leaves the warehouse.

Can I return it if I ordered the wrong part?

Unopened, uninstalled items can be returned within 30 days. Equipment that has been installed or plumbed cannot be returned, so confirm fitment before installation.

Is this covered by a warranty?

Manufacturer warranty terms vary by brand and product. Warranty claims generally require proof of purchase and, on installed equipment, evidence of professional installation.