Pentair ETi 400 High-Efficiency Gas Pool Heater
A high-use pool or pool-and-spa where the fuel bill is the deciding factor, and an owner willing to pay premium money up front and manage a condensing heater's condensate.
Gas heater
SKU ETi 400
- BTU input
- 400,000 BTU/hr
- Fuel / power
- Natural gas
- Thermal efficiency
- 96% thermal efficiency (tested per ANSI Z21.56:19/CSA 4.7:19 2019, section 5.10)
- Heat exchanger
- Titanium
- Warranty
- Parts: 3 years · Labor: 3 years
- Controls & automation
- Digital display with Pool On / Spa On / Heater Off, Service System and Service Heater indicator lights, a five-error code history and readouts for both stack flue sensors; 2-wire dry contact for IntelliCenter, IntelliTouch or EasyTouch.
Modern Pool Heating Equipment Score
Our score for the equipment itself. It is not a Google or customer review rating.
How we rate heatersFull specifications
Every row below is taken from a manufacturer document. Anything the manufacturer does not publish is left out rather than estimated.
| Manufacturer model | ETi 400 High Efficiency Heater, natural gas, ASME listed, P/N 461113 |
|---|---|
| BTU input | 400,000 BTU/hr |
| Thermal efficiency | 96% (tested per ANSI Z21.56:19/CSA 4.7:19 2019, section 5.10) |
| Heat exchanger | Titan-Tough direct-fire titanium, ASME certified construction; design temperature rise 30°F ±5°F |
| Fuel | Factory configured for natural gas; propane conversion kit P/N 476072 available |
| Emissions and certification | Certified for low NOx emissions by a third-party test lab and communicated to SCAQMD for Rule 1146.2; ASME certified, CSD-1 compliant, CSA certified to ANSI Z21.56/CSA 4.7 |
| Water flow | 40 GPM minimum, 120 GPM maximum (external bypass required above 120 GPM); maximum ΔT 35°F, minimum ΔT 25°F |
| Gas supply pressure | Natural gas 4" w.c. minimum to 10.5" w.c. maximum; propane 4" to 12" w.c.; maximum pressure change 2" w.c. |
| Gas pipe sizing (natural gas) | 3/4" not permitted; 1" to 20 ft, 1-1/4" to 90 ft, 1-1/2" to 200 ft |
| Venting | Category IV; Schedule 40 PVC, Schedule 80 CPVC or stainless steel. 4" pipe to 120 ft or 6" pipe to 300 ft, less 12 ft per 90° elbow and 6 ft per 45°. Vent gas under 170°F. With 4" pipe the Combustion Air Intake Kit (P/N 475971) must be installed; intake and exhaust at least 36" apart. |
| Condensate | 2 to 4 gallons per hour. Condensate Neutralizer Kit (P/N 475612) strongly recommended; horizontal vent runs slope back toward the heater at 1/4 inch per foot so condensate drains through the neutralizer. |
| Electrical | 120 or 240 VAC, 60 Hz, single phase; 15 A circuit; about 5 A at 120 VAC or 2.5 A at 240 VAC |
| Clearances | 6" from combustible surfaces on the top, exhaust side, header side and door panels; 3 ft between a roof or deck overhang and the top of the exhaust vent; 36" from an air conditioner, heat pump or another gas heater |
| Dimensions and weight | 40" L x 30" W x 46" H; 365 lb crate weight |
| Safety and diagnostics | Two stack flue sensors (SFS activates at 170°F, thermal fuses at 187°F), two automatic gas shut-off switches (150°F), high limit (135°F), air flow switches, water pressure switch and condensate float switch; last five error codes readable from the control pad |
| Controls and automation | 2-wire dry contact through the fireman's switch terminals for IntelliCenter, IntelliTouch or EasyTouch Control Systems, or a time clock. Pentair's ETi 400 manual documents no RS-485 connection. 180° rotating control panel for left or right plumbing orientation. |
Why homeowners consider it
- 96% thermal efficiency is the headline and it is genuinely exceptional: Pentair measures it per ANSI Z21.56:19/CSA 4.7:19 section 5.10 and cites the DOE pool heater certification database for the claim that it is the highest in its class. A conventional gas heater puts about 84 cents of every fuel dollar into the water; this one puts 96.
- The heat exchanger is direct-fire titanium with ASME certified construction. For a salt pool or a coastal install, titanium is the material you would pick if the budget allowed, and here it is standard rather than an upgrade.
- Pentair publishes three years parts and labor on the ETi 400, against two years parts and labor on a MasterTemp.
- It is the fastest heater in Pentair's own lineup chart: an estimated 4 hours 20 minutes to raise a 20,000-gallon pool by 10°F, and 23 minutes to raise a 600-gallon spa by 30°F.
- Venting is PVC or CPVC rather than metal flue — 4 inch pipe to 120 feet or 6 inch to 300 feet — which opens up indoor and enclosed installations that a conventional heater cannot do cleanly.
What to know before buying
- It is a condensing appliance and it makes water: Pentair states the heater produces 2 to 4 gallons of condensate per hour. That condensate is acidic, it has to be routed somewhere legal, and Pentair strongly recommends the Condensate Neutralizer Kit (P/N 475612). This is the single biggest practical difference from a MasterTemp.
- Gas line sizing is stricter than the MasterTemp's. Pentair's ETi 400 table shows 3/4 inch pipe is not allowed at all on natural gas; you need 1 inch to 20 feet, 1-1/4 inch to 90 feet or 1-1/2 inch to 200 feet.
- Gas supply pressure has a tighter window than the MasterTemp: 4 to 10.5 inches w.c. on natural gas (4 to 12 on propane), with no more than a 2 inch pressure change.
- No RS-485 automation port. The ETi 400 manual documents a 2-wire dry contact connection for IntelliCenter, IntelliTouch or EasyTouch through the fireman's switch — which means on/off control, not the full networked integration the MasterTemp gets.
- It is physically much bigger and heavier than a MasterTemp — roughly 40 inches by 30 inches by 46 inches and 365 pounds crated, against a MasterTemp's 23 by 21 by 28 inches and 136 pounds. Measure the pad before you order.
- Premium price tier. The efficiency only pays back if you actually run the heater a lot; on a pool that gets heated six weekends a year, a MasterTemp HD will cost less to own.
Warranty, term by term
The warranty only matters on the parts that actually fail. Here is how this one splits up.
- Parts
- 3 years
- Labor
- 3 years
Pentair publishes 3 years parts and labor for the ETi 250 and ETi 400 high-efficiency heaters, consistent with the owner's comparison guide. The same channel conditions apply as to the rest of the line: the heater must be bought from a brick-and-mortar retailer, pool builder or pool service company and installed by a qualified professional who charges a fee. A heater bought from an internet retailer is covered for 1 year parts only with no labor. Registration is required. Professional installation and authorized-channel requirements apply.
Why the heat exchanger matters
The heat exchanger is the part of a pool heater that actually moves heat into the water, and what it is made of decides how long the heater survives Florida water chemistry. Here is what the four materials mean in practice.
- Copper
- The traditional material and the cheapest to build. It transfers heat well and is fine on a well-balanced chlorine pool, but it is the least forgiving of low pH, high chlorine and salt. On the Gulf Coast it is usually the first component to fail.
- Cupro-nickel
- Copper alloyed with nickel. It gives up a little heat transfer in exchange for much better resistance to unbalanced water chemistry and salt. On gas heaters this is the upgrade worth having in Florida, and some manufacturers now ship it as standard.
- NiTek (nickel alloy)
- A nickel-alloy exchanger used on some gas heaters as a corrosion-resistant alternative to copper. Positioned between cupro-nickel and titanium in both durability and price.
- TitaniumThis heater
- Effectively immune to pool water chemistry, including salt. It is the standard on quality pool heat pumps and the reason a heat pump can sit on a salt pool for years without exchanger trouble. It is expensive, which is why you rarely see it on gas heaters.
Whatever the material, plumbing order matters just as much: a chlorinator or salt cell belongs downstream of the heater, never upstream.
How we scored it
- Three years parts and labor, against two years on a MasterTemp, is the reason warranty scores high; it loses half a point only for the same channel conditions that apply across the brand.
- A direct-fire titanium exchanger with ASME certified construction is the best corrosion answer available in a gas heater, which is a straight 5 on durability.
- 96% thermal efficiency, verified against Pentair's test standard and the DOE certification database, is a full 5 — no conventional gas heater is close.
- Serviceability is the honest weak point. It is a condensing appliance with a neutralizer cartridge, condensate routing, two stack flue sensors and two gas shut-off switches, and far fewer of them are in the field than MasterTemps, so fewer technicians have opened one.
- Controls score a 4: the dry-contact integration with IntelliCenter, IntelliTouch and EasyTouch is normal for a gas heater, but Pentair's own MasterTemp does better with a true RS-485 connection.
- Value is the lowest score. The heater is excellent and the price tier is genuinely premium; the efficiency only repays a pool that is heated hard, which is why we do not quote it by default.
- The computed score sits below the owner's 4.8 starter score for the ETi 400. The difference is entirely serviceability and automation — the efficiency, exchanger and warranty scores are as high as we give.
Real Modern Pool Heating installations
We have not published a job-site photo for this exact model yet. Installation photos on this site are only ever our own work, and we label each one as the exact model or as a representative install.
Installed locally, researched for everyone
Affordable Solar & Pool Heating, LLC installs and services pool heating in Sarasota, Manatee, Charlotte & Pinellas County, Florida. If you are outside that area this page is still yours to use — take the questions on it to your local contractor. Pool heater installation in Sarasota.
Other heaters worth putting beside it
Same job, different tradeoffs. Every one of these has its own verified spec page.
Pentair · MasterTemp HD
Pentair MasterTemp 400HD Heavy Duty Gas Pool Heater
Model MasterTemp 400HD
- BTU input
- 400,000 BTU/hr
- Thermal efficiency
- 82%
- Heat exchanger
- Cupro-nickel
- Warranty
- 2-Year Parts & Labor
- Wi-Fi / automation
- Automation Compatible
A large salt-water or coastal pool, or a pool and spa that gets used hard, where the exchanger material matters more than the last two points of efficiency.
Raypak · AVIA
Raypak AVIA 404A Gas Pool & Spa Heater
Model P-R404A-EN-C
- BTU input
- 399,000 BTU/hr
- Thermal efficiency
- 84%
- Heat exchanger
- Copper
- Warranty
- 3-Year Parts & Labor
- Wi-Fi / automation
- Wi-Fi Built InAutomation Compatible (Relay)
A large Florida pool, or a pool and spa, where the owner wants spa-speed output and three years of parts and labor cover.
Hayward · Universal H-Series
Hayward Universal H-Series H400FDN Gas Pool Heater
Model H400FDN
- BTU input
- 399,900 BTU/hr
- Thermal efficiency
- 84%
- Heat exchanger
- Cupro-nickel
- Warranty
- 3-Year Parts / 1-Year Labor
- Wi-Fi / automation
- App Control via AutomationAutomation Compatible (Relay)
A large Florida pool, or a pool and spa combination, that needs to reach temperature on demand rather than hold it all season.
ETi 400 questions
Is 96% efficiency really worth the extra money?
It depends entirely on how much you run the heater. Pentair's own arithmetic is that a conventional gas heater puts about $0.84 of every fuel dollar into the water and the ETi 400 puts $0.96. On a pool heated hard through the winter, that gap adds up quickly. On a pool heated six weekends a year it will not repay the price difference over a MasterTemp HD.
What is a condensate neutralizer and do I need one?
The ETi 400 is a condensing heater and produces 2 to 4 gallons of acidic condensate per hour while it runs. A neutralizer cartridge (Pentair P/N 475612) treats that water before it drains. Pentair says neutralizers are not always required but strongly recommends one, and local plumbing codes often settle the question for you. It is a consumable — plan to replace the cartridge.
Will it work on a salt water pool?
Yes, and it is the best gas answer for one. The direct-fire heat exchanger is titanium, which is the material heat pump manufacturers use for exactly this reason. Plumbing order still matters: the salt cell or chemical feeder belongs downstream of the heater with a check valve.
Can it run on propane?
Yes, with Pentair's propane gas conversion kit (P/N 476072). The heater ships configured for natural gas, and the conversion is a qualified-technician job. Gas supply pressure on propane is 4 to 12 inches w.c. rather than 4 to 10.5.
Does it integrate with Pentair automation?
It connects to IntelliCenter, IntelliTouch or EasyTouch through a 2-wire dry contact on the fireman's switch terminals, which gives the automation system on/off control of the heater. Unlike the MasterTemp, Pentair's ETi 400 manual documents no RS-485 communication port, so the heater's own faults do not appear on the automation panel.
Do you install the ETi 400 locally?
Yes. We install and service Pentair gas heaters, including the ETi line, throughout Sarasota, Manatee, Charlotte & Pinellas County, Florida. Because of the condensate and venting requirements we always look at the pad before quoting one. The comparison content here is written for pool owners anywhere; the installation offer is local.
Is the ETi 400 right for your pool?
We install and service pool heating in Sarasota, Manatee, Charlotte & Pinellas County, Florida. If you are outside that area, the comparison above is still yours to use — ask your local contractor the same questions.
Licensed & insured · Florida Certified Pool/Spa Contractor #CPC1460367 · Mon-Sat, 8am-6pm
Last verified September 17, 2026
Specifications and warranty terms are taken from the manufacturer documents below. Manufacturers revise these without notice, so confirm the current terms before you buy. If you spot something out of date, email us and we will fix it.
Sources
- Pentair — ETi 400 Installation and User's Guide (flow, gas pressure, clearances, electrical, error codes)
- Pentair — ETi 400 Quick Reference Guide (venting, gas line sizing, condensate, certifications)
- Pentair — 2025-2026 Pool Product Catalog, Heaters & Heat Pumps section (June 2025)
- Pentair — High-Performance Pool & Spa Gas Heaters brochure (efficiency, exchanger, dimensions, heat-up times)
- Pentair — Pool product warranty information (parts, labor, compressor, exchanger terms and channel conditions)
Ratings on this site are the editorial opinion of Affordable Solar & Pool Heating, LLC, trading as Modern Pool Heating. How we rate heaters. Corrections: modernpoolheating@icloud.com.
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Mon-Sat, 8am-6pm · Licensed & insured · Florida Certified Pool/Spa Contractor CPC1460367