Quick answer: For a Raypak Digital 266K (or the broader 2100/RP2100 series), the OEM cupro-nickel tube bundle is part 010365F, running roughly $1,377-$2,327. A Pentair MasterTemp 400 uses OEM part 474061 (Tube Sheet Coil Assembly Kit), around $1,080-$1,625. A Hayward Universal H400FDN uses copper exchanger assembly FDXLHXA1400, typically $1,499-$1,600. AquaCal/Gulfstream HE-RA heat pumps use a titanium exchanger sold by BTU rating rather than one universal part number, generally landing in the $700-$1,800 range per AquaCal’s own dealer network. In every case, this is one repair worth getting a written quote for before you commit — not a part to install yourself.
A heat exchanger failing is expensive news, but it’s also one of the least common failures on a well-maintained heater. Our own parts lifespan research found that a heat exchanger built from cupro-nickel or titanium routinely lasts 10 years or more with good water chemistry, versus the 3-5 years electronic parts like igniters and sensors typically manage. When one does fail early, it’s almost always one of two causes: freeze damage from a skipped winterization, or years of pH swings slowly corroding the tubing from the inside — see the Pool & Hot Tub Alliance’s pH-management guidance for why that one number matters more than brand or price tier.
Heat exchangers at a glance
| Part | Fits | Material | Price |
|---|---|---|---|
| Raypak 010365F | Digital 266K / 2100 series (pre-7/2013 build; verify by serial) | Cupro-nickel | $1,377-$2,327 |
| Pentair 474061 | MasterTemp 400NA/400LP (mfg. after 1/12/09) | Copper | $1,080-$1,625 |
| Hayward FDXLHXA1400 | Universal H400FDN/H400FD | Copper | $1,499-$1,600 |
| AquaCal/Gulfstream Titanium | HE-RA lineup (matched by BTU: 90K/110K/125K) | Titanium | ~$700-$1,800 |
1. Raypak 010365F — For Digital 266K & 2100 Series
Raypak 010365F Cupro-Nickel Tube Bundle
- Raypak changed tube-bundle part numbers across production runs of the same model name, so confirm the fit against your unit's serial number with a dealer before ordering — don't order off the model number alone.
- Cupro-nickel is Raypak's standard exchanger material on this line specifically for corrosion resistance against chlorinated and salt pool water.
- Our Raypak review covers the Digital 266K's other specs if you're deciding whether to repair this unit or replace it outright.
- Price varies unusually widely by retailer for this part — get at least two quotes before a tech orders it on your behalf.
2. Pentair 474061 — For MasterTemp 400
Pentair 474061 Tube Sheet Coil Assembly Kit
- Units manufactured before 1/12/09 use a different part number (77707-0234) — check your heater's data plate build date, not just the model number, before ordering.
- A smaller MasterTemp 250 uses a different, less expensive exchanger (474059, roughly $1,070) — the price scales with the unit's BTU output, not just the brand.
- Our Pentair MasterTemp review has the full model lineup if a replacement quote has you weighing a new unit instead.
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3. Hayward FDXLHXA1400 — For Universal H400FDN
Hayward FDXLHXA1400 Heat Exchanger Assembly
- Unlike Raypak, Hayward's Universal H-Series uses a single exchanger assembly across the FDN/FD variants at this BTU size, which simplifies part lookup.
- This is a copper build, not cupro-nickel — Hayward reserves cupro-nickel construction for its higher-tier commercial and saltwater-rated lines.
- See our Hayward vs. Pentair comparison if a repair quote this size has you weighing a straight swap to the other brand.
4. AquaCal/Gulfstream Titanium Exchanger — For HE-RA Heat Pumps
AquaCal/Gulfstream Titanium Heat Exchanger
- AquaCal sells this part by BTU rating rather than a single universal SKU, and pricing isn't publicly listed — a dealer or AquaCal's own tech support confirms the exact part against your unit's serial number.
- Titanium, not copper or cupro-nickel, is the standard here because a heat pump's refrigerant coil sits in direct water contact, and titanium handles saltwater and heavy chlorine better than either alternative.
- This job additionally requires EPA-certified refrigerant recovery before the coil can even be accessed — confirm your technician holds an EPA 608 certification, since it's a legal requirement, not just a best practice.
- Our Gulfstream heat pump review covers the HE-RA lineup's other wear parts if the exchanger turns out not to be the actual issue.
Why this is always a licensed-tech job
Every exchanger on this list sits behind either combustion safety or refrigerant handling, which is exactly why it’s the one repair category we don’t frame as DIY-friendly anywhere on this site. Gas-heater swaps mean draining and isolating the unit, removing header and manifold gaskets, and torquing tube-sheet seals to a precise spec — get any of that wrong and you have a combustion leak, not a pool heater. Heat pump swaps go a step further: the exchanger sits inside a sealed refrigerant circuit, so a technician has to legally hold an EPA 608 certification to recover the refrigerant before the old coil can even come out. Our parts guide covers which repairs are genuinely DIY-friendly (pressure switches, thermostats, igniter kits) so you know which end of that spectrum you’re on before calling anyone.
Repair or replace? Apply the 50% rule
At $900-$2,300 in parts alone before labor, a heat exchanger repair routinely brushes up against — or exceeds — half the price of a new heater, which is the threshold most pool pros use to recommend replacement instead. Our repair cost guide breaks down exactly where that line falls by heater type, and it matters more the older the unit is: most gas and heat pump heaters are expected to need major work somewhere in the 7-10 year range according to our heater lifespan breakdown, so a four-figure exchanger quote on a heater already near that age rarely pencils out. A heater still in its first several years is the clearer case for repairing rather than replacing.
The bottom line
A failed heat exchanger is the most expensive single-part repair a pool heater owner will face outside of a heat pump compressor, and correctly so — it’s the core component the rest of the unit is built around. The Raypak 010365F, Pentair 474061, Hayward FDXLHXA1400, and AquaCal/Gulfstream titanium exchanger cover the major brands already reviewed on this site, but every one of them belongs in a licensed technician’s hands, not a DIY project. Get a written quote first, run it against the 50% rule above, and if the number is closer to a new heater’s price than a repair’s, our pool heater picks are the better next stop. If the actual leak is coming from the manifold or header gaskets rather than the exchanger’s tube bundle itself, our manifold and header guide covers that cheaper, separate repair by brand.
Sources: InyoPools — Raypak RP2100 Parts, PoolSupplyUnlimited — Pentair MasterTemp Heat Exchanger Parts, Sunplay — Hayward H400FD Heat Exchanger, PoolHeatPumps — Gulfstream Titanium Heat Exchanger