Pentair MasterTemp Gas Heater Buying Guide
When you need your pool heated fast — for a weekend swim, a spa session or just to take the edge off on a cool Sydney evening — a gas heater delivers in a way nothing else can. The Pentair MasterTemp is one of the most trusted gas pool heater ranges in Australia, and for good reason.
In this guide we compare the MasterTemp 125, 250, 300 and 400, walk you through how to size a gas heater correctly, and help you decide whether gas heating is right for your pool.
In this guide
Gas Heater vs Heat Pump — Which Should You Choose?
This is the first question to answer before looking at any specific model. Both will heat your pool — but they suit different situations.
| Feature | Gas Heater | Heat Pump |
|---|---|---|
| Heating speed | Fast — heats pool on demand | Slower — better for maintaining temperature |
| Running cost | Higher — burns gas continuously | Lower — very energy efficient |
| Best for | Occasional use, quick heat-up, spas | Regular swimming, year-round heating |
| Works in cold weather | Yes — not affected by air temperature | Less effective below 10°C |
| Upfront cost | Lower | Higher |
| Long-term running cost | Higher | Lower |
Gas heaters are best for: Pool owners who swim occasionally and need the pool heated quickly on demand — or those with a spa that needs to reach high temperatures fast. They're also not affected by ambient air temperature, making them reliable in any weather.
If you swim regularly and want to keep running costs low, a heat pump like the Madimack may be a better fit.
How Does a Gas Pool Heater Work?
A gas pool heater burns natural gas or LPG to heat a copper heat exchanger. Pool water circulates through the exchanger, picks up the heat, and returns to the pool at a higher temperature. It's straightforward, fast and reliable.
The MasterTemp uses pre-mixed combustion technology — gas and air are mixed before ignition, which delivers more efficient and cleaner combustion than traditional designs. This gives it an 82% thermal efficiency rating — excellent for a gas heater.
How to Size a Gas Heater for Your Pool
Gas heaters are rated in BTU (British Thermal Units) per hour. The higher the BTU, the faster the heater heats the pool. Choosing the right size comes down to your pool volume and how quickly you want to heat it.
| Pool Size | Recommended Model | Approx Heat-Up Time |
|---|---|---|
| Spas & pools up to 40,000L | MasterTemp 125 | Longer — best for maintaining temp |
| Medium pools 40,000–70,000L | MasterTemp 250 | Moderate heat-up time |
| Large pools 60,000–80,000L | MasterTemp 300 | Fast heat-up for large pools |
| Very large pools 80,000L+ | MasterTemp 400 | Fastest heat-up in the range |
MasterTemp 125
The entry point to the MasterTemp range — lightweight, compact and surprisingly capable for its size.
MasterTemp 125
125,000 BTU/hr output
82% thermal efficiency
Pre-mixed combustion technology
Hot-surface ignition — no pilot light
Digital LCD display
1.5" plumbing connection
Lightweight — approx 36kg
Spas & smaller poolsBest for: Spas, above-ground pools and inground pools up to 40,000L. A popular choice where installation space is limited or where you mainly need to top up temperature rather than heat from cold.
MasterTemp 250
The mid-range model — a great all-rounder for most residential pools in Sydney.
MasterTemp 250
250,000 BTU/hr output
Low-NOₓ certified
82%+ thermal efficiency
Copper heat exchanger
Hot-surface ignition
Rotating digital LCD controller
UV and corrosion-resistant housing
Medium pools & spasBest for: Most standard residential pools in the 40,000–70,000L range. The 250 gives you genuinely fast heat-up times and low NOₓ emissions — a solid choice for everyday pool heating in Sydney.
MasterTemp 300
The MasterTemp 300 sits between the 250 and 400 — a strong performer for larger pools that don't quite need the full output of the 400.
MasterTemp 300
300,000 BTU/hr output
Low-NOₓ certified
82%+ thermal efficiency
Copper heat exchanger
Hot-surface ignition
Rotating digital LCD controller
UV and corrosion-resistant housing
Large poolsBest for: Larger pools in the 60,000–80,000L range where the 250 may struggle to heat quickly enough but the 400 feels like overkill. The 300 is a popular choice for pool owners who want fast heating without going to the top of the range.
MasterTemp 400
The most powerful model in the range — for large pools or anyone who wants the fastest possible heat-up time.
MasterTemp 400
400,000 BTU/hr output
Low-NOₓ certified
Copper heat exchanger
Hot-surface ignition
Rotating digital LCD controller
Compatible with Pentair automation systems
UV and corrosion-resistant housing
Large poolsBest for: Large pools (70,000L+), pool owners who want the pool ready to swim in as quickly as possible, or those integrating with a Pentair automation system like IntelliCenter or EasyTouch.
Model Comparison — 125 vs 250 vs 300 vs 400
| Feature | MasterTemp 125 | MasterTemp 250 | MasterTemp 300 | MasterTemp 400 |
|---|---|---|---|---|
| Output | 125,000 BTU/hr | 250,000 BTU/hr | 300,000 BTU/hr | 400,000 BTU/hr |
| Efficiency | 82% | 82%+ | 82%+ | 84% |
| Low NOₓ | No | Yes | Yes | Yes |
| Plumbing connection | 1.5" | 2" | 2" | 2" |
| Best pool size | Spas & pools up to 40,000L | Medium pools | Large pools | Very large pools |
| Automation compatible | Basic | Yes | Yes | Yes — full integration |
| Weight | ~36 kg | ~50 kg | ~54 kg | ~57 kg |
Natural Gas vs LPG
The MasterTemp range is available in both natural gas and LPG (propane) configurations. Here's how to decide:
- Natural gas — if you have a gas connection to your home, this is the more cost-effective option. Natural gas is generally cheaper per unit of energy than LPG in Australia
- LPG — if you don't have a natural gas connection, LPG is the alternative. You'll need a tank installed on your property
Installation Requirements
The MasterTemp must be installed by a licensed gas fitter and plumber. Key things to know:
- Gas connection: Adequate gas supply line and pressure is required — your gas fitter will check this
- Venting: The MasterTemp can be installed indoors or outdoors but must be properly vented — follow Pentair's installation manual and local codes
- Plumbing: Installed inline with your filtration system — between the filter and return line
- Clearances: Maintain required clearances from combustible materials, walls and neighbouring properties
- Electrical: Requires a 240V supply for the ignition system and controls
Running Costs
Gas heaters are more expensive to run than heat pumps, but they're used differently — typically for shorter bursts of heating rather than continuous operation. Running costs depend on:
- Your local gas tariff (natural gas is generally cheaper than LPG)
- How often you use the heater and for how long
- Whether you use a pool cover to retain heat between sessions
- Your target pool temperature
Our Verdict
The Pentair MasterTemp is a well-engineered, reliable gas heater that's been a trusted choice for Australian pool owners for years. If you need fast on-demand heating and have a gas connection, it's hard to fault.
- Best for spas and small pools: MasterTemp 125
- Best all-rounder for most Sydney pools: MasterTemp 250
- Best for large pools: MasterTemp 300
- Best for very large pools or maximum speed: MasterTemp 400
- Want lower running costs instead? Consider our Madimack heat pump buying guide
Need help choosing the right gas heater?
Come in to our Gordon store or give us a call — we'll help you choose the right MasterTemp model for your pool size and heating needs. No obligation, just honest advice.
Shop Gas Heaters → Call 02 9499 9646