Quick answer: For Raypak AVIA heaters with polymer headers (and the RP2100 R185A-R405A digital line), the correct part is the Raypak 006721F drain plug kit (Capron nylon plastic, includes O-ring, around $28). Pentair and Sta-Rite MasterTemp, ETi 250/400, and Max-E-Therm heaters use the Pentair U178-920P ($7.95-$11.99). Hayward Universal H-Series heaters (H150FDN through H500FD) take the Hayward SPX4000FG ($5.99-$12.99) — the same part number Hayward sells for several of its pump lines. Jandy/Zodiac LRZE and LRZM heaters use the Zodiac R0446000 2-pack ($25.05), also shared with several Jandy pump models. A leaking drain plug is one of the cheapest, easiest-to-fix leaks a pool heater can have, and a worn O-ring left over from last season’s winterizing is a documented cause of small post-opening leaks.
A drain plug is a small part doing an unglamorous job: it seals the low point of the heat exchanger header so you can fully empty the heater before a freeze, rather than hoping gravity clears every trapped pocket of water on its own. Because it’s threaded and O-ring-sealed rather than welded or gasket-bonded, it’s also one of the first places a small leak shows up — especially right after spring startup, when a plug that was pulled for winterizing goes back in with a flattened or dirt-fouled O-ring. Pooltivity’s own post-opening leak troubleshooting guide lists checking “the plug is installed, gasket is intact, and threads are not damaged” as a specific diagnostic step for exactly this reason.
Pool heater drain plugs at a glance
| Drain plug | Fits | Material | Price |
|---|---|---|---|
| Raypak 006721F | AVIA (polymer header), RP2100 R185A-R405A | Capron nylon plastic | ~$28 |
| Pentair U178-920P | MasterTemp, ETi 250/400, Max-E-Therm | Not disclosed by manufacturer | $7.95-$11.99 |
| Hayward SPX4000FG | Universal H-Series H150FDN-H500FD (shared with pump lines) | Not disclosed by manufacturer | $5.99-$12.99 |
| Zodiac/Jandy R0446000 (2-pack) | LRZE, LRZM (shared with pump lines) | Polymer | $25.05 |
1. Raypak 006721F — For AVIA & RP2100 Digital
Raypak 006721F Drain Plug Kit (Capron Nylon, with O-Ring)
- Raypak's own instruction sheet (P/N 241979) specifies this kit "for AVIA pool & spa heaters with polymer headers" — Capron nylon plastic rather than brass, so over-tightening it against a metal header is the fastest way to crack it.
- A gray version, Raypak 100-10008775, is also listed for some current AVIA units — confirm the exact plug color/part number against your heater's rating plate before ordering, since Raypak has run both in parallel.
- The highest-priced plug on this list at around $28 for what's a small nylon fitting, mostly because it's sold as a kit with a matched O-ring rather than the bare hardware-store equivalent.
- This is the same polymer-header family referenced in our manifold and header guide — if a technician is already draining and resealing the header for a manifold job, that's a natural time to swap the drain plug O-ring too.
Warm up your pool sooner — try Amazon Prime free for 30 days and get your pool heater delivered in two days.
2. Pentair U178-920P — For MasterTemp, ETi & Max-E-Therm
Pentair U178-920P Drain Plug with O-Ring
- Listed as item #20, "Drain Plug," on Pentair's own MasterTemp water-system parts diagram — the cheapest plug on this list and a straightforward hand-tight swap.
- Neither Pentair's parts page nor the retailers carrying it disclose the plug material — don't assume brass or plastic on this one specifically, and inspect the old part before ordering if you want a like-for-like match.
- Same MasterTemp/Max-E-Therm family covered by our manifold kit and pressure switch guides — all three sit on the same water-system casting.
- If the leak shows up right after spring startup rather than gradually over the season, a degraded O-ring left over from winterizing is the most likely cause, not a new failure.
3. Hayward SPX4000FG — For Universal H-Series (Shared With Pumps)
Hayward SPX4000FG Drain Plug with O-Ring
- The same SPX4000FG part number covers Hayward's Universal H-Series heaters and several of its pump lines — EcoStar, TriStar, and Super Pump among them — a genuine "one part, two product categories" case rather than a heater-exclusive plug.
- Material isn't disclosed by Hayward or the retailers carrying it — treat any brass-vs-plastic claim for this specific part as unverified.
- Least expensive of the four brands here at $5.99-$12.99, in line with it being shared hardware rather than a heater-specific casting.
- The same "FD" model-range designation used across this site's other Universal H-Series OEM parts, including the igniter and pressure switch guides.
4. Zodiac/Jandy R0446000 — For LRZE & LRZM (Shared With Pumps)
Zodiac/Jandy R0446000 Drain Plug 2-Pack, with O-Rings
- Sold as a 2-pack — practical since a heater typically has more than one drain point, and it means you have a spare O-ring on hand the next time you winterize.
- Like Hayward's SPX4000FG, this part number is shared across Jandy's ePump, Stealth, PlusHP, and FloPro pump lines, not exclusive to heaters — confirmed as polymer construction, unlike Pentair's and Hayward's undisclosed material.
- Jandy's current JXi and LXi Low-NOx lines are covered separately by this site's manifold gasket kit guide — check your model designation (LRZE/LRZM vs. JXi/LXi) before ordering, since Jandy's older and newer gas-heater platforms don't share every fitting.
Is it really the drain plug?
A drain-plug leak has a distinctive signature: water beading or dripping from one specific threaded fitting near the base of the heater, not from the casting seam (that’s a manifold or header problem) and not appearing only when the heater is actively firing (that points toward condensation instead). Our leak repair guide’s dry-and-watch test — towel off the pad, run the pump with the heater off, and watch with a flashlight — pinpoints it in a few minutes. If the drip is coming from that exact plug and nowhere else, pulling it, wiping the O-ring groove clean, and reseating a fresh O-ring (or the whole kit, since they’re cheap) resolves it in most cases without touching anything else on the heater.
The bottom line
A drain plug is about as low-stakes as pool heater repairs get — $6-$28 in parts across all four brands here, and a hand-tools job that takes minutes rather than the technician-grade work a manifold or heat exchanger swap requires. Match the exact part number to your model and header material — Raypak’s polymer-header AVIA plug isn’t interchangeable with its older metal-header parts, and Hayward’s and Jandy’s plugs double as pump hardware, so double-check you’re ordering the heater-fitment listing. If the leak turns out to be coming from somewhere other than the plug itself, our leak repair guide walks through the rest of the water-side failure points by cost and DIY-vs-technician difficulty.
Sources: Raypak — AVIA Drain Plug Kit Instruction Sheet 241979, Aqua Pool Supply — Raypak 006721F Drain Plug Kit, Sunplay — Pentair U178-920P Drain Plug, DiscountPoolMart — Hayward SPX4000FG Drain Plug, PoolWeb — Zodiac R0446000 Drain Plug 2-Pack, Pooltivity — Pool Heater Leaking After Opening