Pentair Sta-Rite Max-E-Thermostat 400K BTU Heater SR400NA – Natural Gas Pool & Spa Heating
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The Pentair Sta-Rite Max-E-Therm SR400NA Natural Gas Pool & Spa Heater delivers powerful 400,000 BTU heating performance in a compact, energy-efficient design. Built for fast heat-up times and reliable operation, Max-E-Therm heaters are trusted for both residential and light commercial pool and spa installations.
Featuring a high-efficiency copper heat exchanger, advanced digital controls, and a corrosion-resistant composite cabinet, the SR400NA provides consistent temperature control while operating quietly and efficiently. Its space-saving footprint and straightforward installation make it an excellent choice for equipment pads with limited room—without sacrificing heating power.
Frequently asked questions
How do I size a pool heater?
Heater sizing follows pool surface area, the temperature rise you want and how exposed the pool is to wind. A larger BTU rating heats faster and cycles less; an undersized heater runs continuously and still struggles on cold nights. Gas heaters also need a gas line and meter capacity that can supply their rated input.
What is the part number for this heater component?
Sta-Rite lists this heater component under part number SR400NA. Quote SR400NA when you cross-reference against your equipment manual, an existing part, or a parts diagram, so you are comparing the same revision.
What routine maintenance does a pool heater need?
Keep water chemistry balanced, because low pH and high calcium hardness are the two most common causes of premature heat exchanger failure. Beyond that: keep the cabinet clear of debris, check for rodent nests before each season, and have the burner and gas train inspected periodically.
How do I confirm this fits my equipment?
Match the part number stamped on the component you are replacing, or look it up in the parts list for your Sta-Rite equipment. If your model or serial number is not named on this page, send it to us before you order and we will confirm the fit.
Is this the complete heater or a replacement part?
Check the title and the specification section above. Heater listings and heater component listings share the same part-number format, so confirm whether you are buying a full appliance or a single serviceable component before ordering.
Is there a warranty on this heater component?
It carries the standard Sta-Rite manufacturer warranty. The terms are set by Sta-Rite, and on some equipment the coverage only applies when a licensed professional performs the installation. Keep the receipt and packaging until you have confirmed correct operation.