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Pentair MasterTemp 400 Natural Gas Heater vs Pentair MasterTemp 125K BTU Pool Heater

These are the same MasterTemp family at very different sizes. The 460736 is a 400,000 BTU natural gas unit built for large pools and fast spa heat; the 461061 is a 125,000 BTU propane unit for pools up to about 15,000 gallons and spas. Owners and reviewers of the MasterTemp line praise quick heat-up, quiet induced-draft operation and straightforward installation, and both use copper heat exchangers and digital controls. Buy the 400K for a big pool on natural gas; buy the 125K for a small pool or spa on propane.

  • Choose the Pentair MasterTemp 400 if you have natural gas service and a large pool or spa that needs fast heat-up.
  • Choose the Pentair MasterTemp 125 if you have a propane supply and a pool up to about 15,000 gallons or a spa.

Prices

  • Pentair MasterTemp 400 Natural Gas Heater: $3,639.00 at PoolSupply 4U (checked today)
  • Pentair MasterTemp 125K BTU Pool Heater: $1,736.12 at Pool Supply Harbor (checked today)
  • Difference: the Pentair MasterTemp 125K BTU Pool Heater is $1,902.88 cheaper than the Pentair MasterTemp 400 Natural Gas Heater today
Pentair
Pentair Mastertemp 400K BTU Heater Natural Gas 460736

Pentair MasterTemp 400 Natural Gas Heater

Pentair Mastertemp 400K BTU Heater Natural Gas 460736

4.8(27 ratings)
$3,639.00at PoolSupply 4UChecked 19 h ago
See all prices and details
Visit PoolSupply 4U
Pros
  • 400,000 BTU heats large pools and spas quickly
  • Low-NOx combustion and 82–84% efficiency
  • Hot-surface ignition with no standing pilot
  • Digital controls with built-in diagnostics
  • Reversible water connections ease installation
Cons
  • Natural gas only, so no propane option
  • Needs 2-inch plumbing and hardwired power
  • Oversized for small pools and spas
Pentair
Pentair MasterTemp Pool Heater 461061

Pentair MasterTemp 125K BTU Pool Heater

Pentair MasterTemp Pool Heater 461061

$1,736.12at Pool Supply HarborChecked 19 h ago
See all prices and details
Visit Pool Supply Harbor
Pros
  • Runs on propane for homes without gas service
  • Factory-supplied power cord simplifies install
  • Quiet operation and smooth digital control
  • UV- and corrosion-resistant housing
  • Works with IntelliCenter, EasyTouch and IntelliTouch
Cons
  • 125,000 BTU is slow for large pools
  • Propane tanks need refilling and space
  • 1-1/2 inch plumbing limits flow versus 2-inch

What separates them

Pentair MasterTemp 400 Natural Gas HeaterPentair MasterTemp 125K BTU Pool Heater
FuelNatural gas onlyPropane (LP)
Heat output400,000 BTU125,000 BTU
Pool sizeLarge residential pools and spasUp to about 15,000 gallons, spas, aboveground pools
Plumbing connection2-inch Schedule 40 PVC1-1/2 inch
Flow rateNot specified in listing20 to 70 gal/min
ElectricalHardwired 120V or 240V120V with factory-supplied power cord
IgnitionHot-surface electronic, no standing pilotElectronic ignition
EnclosureCompact cabinet, indoor/outdoorUV- and corrosion-resistant, outdoor

Price history

$3,639.00$2,129.00
Nov 7Nov 10
  • Pentair MasterTemp 400 Natural Gas Heater: lowest $3,639.00 on Nov 10 at Pool Supply Depot.
  • Pentair MasterTemp 125K BTU Pool Heater: lowest $2,129.00 on Nov 7 at Amazon; $2,129.00 on Nov 10.

Prices at every store

Pentair MasterTemp 400 Natural Gas Heater

  • PoolSupply 4UNew

    In stockReturn policy

    $3,639.00Checked 19 h ago
    Visit PoolSupply 4U
  • Aqua Pool SupplyNew

    In stockReturn policy

    $3,649.94Checked 19 h ago
    Visit Aqua Pool Supply
  • Swimming Pool Supply USANew

    In stockReturn policy

    $3,698.00Checked 19 h ago
    Visit Swimming Pool Supply USA
  • Pool Supply DepotNew

    In stock

    $3,639.00+ $350.00 shippingChecked 19 h ago
    Visit Pool Supply Depot

Also available at

  • PoolCleaningParts.comCheck price at PoolCleaningParts.com
  • Pool Supply DepotCheck price at Pool Supply Depot
All 12 stores and price history →

Pentair MasterTemp 125K BTU Pool Heater

  • Pool Supply HarborNew

    In stockReturn policy

    $1,736.12Checked 19 h ago
    Visit Pool Supply Harbor
  • PoolSupply 4UNew

    In stockReturn policy

    $1,758.99Checked 19 h ago
    Visit PoolSupply 4U
  • AppaeTech Pool SupplyNew

    In stockReturn policy

    $1,758.99Checked 19 h ago
    Visit AppaeTech Pool Supply
  • AmazonNew

    Availability unknown

    As an Amazon Associate, Deal.ai earns from qualifying purchases.

    $2,129.00Free shippingChecked 19 h ago
    Visit Amazon
All 11 stores and price history →

Specs compared

SpecPentair MasterTemp 400 Natural Gas HeaterPentair MasterTemp 125K BTU Pool Heater
Voltagehardwired 120V or 240V120V
Energy Efficiency82%–84%82% energy efficiency
Heater TypeNatural Gas—
BTU Rating400,000 BTU—
Dimensions27×36×35 in.—
Maximum Altitude10,000 ft—
Gas TypeNatural Gas—
LocationIndoor/Outdoor—
Elevation0-9000'—
IgnitionElectronic—
Heating Type—Gas
Pool Size—Up to 15,000 gallons, Smaller bodies of water
Show all 31 specsShow fewer specs
SpecPentair MasterTemp 400 Natural Gas HeaterPentair MasterTemp 125K BTU Pool Heater
Pool Type—Inground pools, Aboveground pools, Spas
BTU Output—125,000 BTU
Heating Capacity—125,000 BTU
Heat Exchanger Type—Copper
Flow Rate—Min: 20 gal/min, Max: 70 gal/min
Power Source—Propane Gas, Natural Gas
Amperage—5A
Control Type—Digital
Depth—60 cm
Height

What reviewers say

Pentair MasterTemp 400 Natural Gas Heater

  • 4.8 / 527 ratings

Owners rate it highly and describe quick spa heat-up and a fairly straightforward install. Most feedback centers on reliability and ease of setup rather than long-term durability.

What people mention
  • Heat-up speedPraisedOwners say it brings a spa or large pool up to temperature quickly.
  • InstallationPraisedBuyers describe the install as relatively easy for a gas heater of this size.
  • EfficiencyMixedThe 82–84% rating is fine for a standard atmospheric heater but trails condensing models.
  • BuildPraisedOwners report the cabinet and copper exchanger holding up well in outdoor installations.

Pentair MasterTemp 125K BTU Pool Heater

Owners of the MasterTemp line generally report fast heat-up and simple digital control. Complaints tend to center on heat exchanger corrosion when water chemistry slips and on the cost of repairs.

What people mention
  • Heat-up speedPraisedOwners say it brings a small pool or spa up to temperature quickly.
  • BuildMixedThe cabinet holds up outdoors, but the copper exchanger is the weak point over time.
  • Water chemistryCriticisedLow pH or high chlorine is blamed for corroded exchangers and early failures.
  • NoisePraisedIt runs quietly compared with older heaters.

Questions and answers

Which is better for a large pool?
The 400K. At 400,000 BTU it heats a large pool far faster than the 125,000 BTU unit, which is rated for pools up to about 15,000 gallons.
Can I use the 400K on propane?
No. The 460736 is natural gas only. If you have propane, the 461061 is the one in this pair built for it.
Which lasts longer?
Both use copper heat exchangers and similar cabinets, so life depends more on water chemistry and correct installation than on the model. Keep pH and chemistry in range and both should give many years of service.
Is the 125K enough for a spa?
Yes. It is sized for spas and small pools and heats them quickly. For a pool much over 15,000 gallons, step up to the 400K.
Do both work with Pentair automation?
The 461061 is listed as compatible with IntelliCenter, EasyTouch and IntelliTouch. The 400K uses standard digital controls; check your automation setup before pairing.
Is one worth stepping up to?
Step up to the 400K if you have natural gas and a large pool, since the extra output cuts heat-up time sharply. Stay with the 125K if you are on propane or heating a spa.

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Buying guides that pick them

  • Best pool heaters
—
60 cm
Width—80 cm
Durability Features—UV-resistant enclosure, Corrosion-resistant enc…
Electrical Requirements—120/240 V
Installation Type—Outdoor, Indoor
Plumbing Connection Size—1-1/2 in.
Location Requirements—Outdoor
Venting Requirements—Low NOx emissions
Noise Level—Quiet Operation, Minimal noise
Safety Features—Low NOx emissions