Pair - 74mm OD "50mm" Balboa / Gecko / Aeware Spa Heater Gasket O-Ring Seal - Pair
Pair - 74mm OD "50mm" Balboa / Gecko / Aeware Spa Heater Gasket O-Ring Seal - Pair is backordered and will ship as soon as it is back in stock.
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PAIR (Two) genuine Balboa / Gecko ribbed heater o-ring gaskets. These seals fit all Balboa 2″ flo-thru heater tubes – including M7 and non-M7 heaters – plus most Gecko, AEware, Hydroquip, Aquatemp, RMF, Spa Builders, and other spa packs that use the standard 2″ heater union. Material colour may vary (black/white/clear).
These seals fit just about every Balboa control system and heater tube ever made, except GS100 & GS200. If your spa has a Balboa VS, GS, GL, EL, BP, LE, Value or metal-box control pack with a 2″ heater, these are the correct gaskets.
Replace every few years or after heavy chemical imbalance to prevent leaks.
Compatibility (Grouped for clarity)
- Balboa control systems: VS Series, GS Series (except GS100 & GS200), GL Mach 3, EL Mach 3, BP Series (BP200/501/601/2100/2600/BP7/BP8), LE Series, Value & older metal-box Balboa packs.
- Balboa heater tubes (2″ flo-thru): 58061, 58063, 58083, 58107, 58118, 58122, 58141, 58143, 58145, 58215, 58301, 58306, 58450, 58454, 58433, and all standard 15″ × 2″ Balboa M7 and non-M7 heaters.
- Additional heater assemblies: Balboa Auxiliary Slave Heater, SCS 501, 55626, 56911, 55614, 50139, 50096, 58053 and other 2″ flo-thru style heaters.
- Gecko / AEware: in.yj, in.ye, in.xe, in.xm, in.xm2, in.xl, SSPA, MSPA, Microspa, and most Gecko AEware 2″ heater tubes.
- SpaPro & WWDG Control Systems: All including SpaPro X1, SpaPro X2, SpaPro X3, and WWDG W1, W3, Wx systems.
- Other brands using 2″ heater unions: Hydroquip, Pentair, Aquatemp, RMF, Spa Builders, Spa-Quip (flo-thru conversions), and many OEM re-badged systems.
Note: Commonly referred to as “50mm” or “2″ heater gaskets”. The 50mm refers to plumbing size – the actual gasket is larger and measures 74mm outside diameter.
Measurements
- Outside Diameter: approx. 74mm
- Inside Diameter: 53mm
- Total Thickness: 6mm
- Raised rib (square-edge side), centre-to-centre: 63mm
Replaces / May be stamped as
- 711-4031
- 21619
- B-21619 / B21619
- RGASHEA50M
- PL-10170
Associated Numbers:
26-58083-K, 26-58118-K, 50mm, 50096, 50139, 53475, 53475-01, 53883, 53883-01, 53883-02, 53883-03, 53883-04, 53885, 53885-01, 53885-02, 53885-03, 53885-04, 53996, 54282, 54282-01, 54282-02, 54282-03, 54282-04, 54297, 54297-01, 54297-02, 54297-03, 54305, 54305-01, 54305-02, 54346, 54346-01, 54406, 54476, 54476-01, 54479, 54479-01, 54479-02, 54501, 54501-01, 54503, 54503-01, 54699, 54705, 54850, 54850-01, 55085, 55085-01, 55087, 55087-01, 55496, 55496-01, 55565, 55595, 55595-01, 55614, 55626, 55866, 55866-01, 55890, 56002, 56002-01, 56002-02, 56002-03, 56002-04, 56004, 56004-01, 56012, 56012-01, 56012-02, 56220, 56282, 56290, 56290-01, 56911, 58053, 58061, 58061-TUV, 58063, 58083, 58107, 58118, 58122, 58141, 58143, 58145, 58215, 58300 Series, 58301, 58306, 58433, 58450, 58454, 711-4031, 21619, B-21619, B21619, PL-10170, RGASHEA50M, Auxiliary Slave Heater, SCS 501
Common search terms: o-ring, oring, Balboa heater gasket, 50mm spa heater seal, Gecko heater gasket, spa heater o-ring, 2 inch heater union seal.
In plumbing, named sizes are not the actual measurements. A pipe called “50mm” or “2"” does not measure 50 mm across. Instead, it follows nominal sizing, an internationally-standardised naming system.
Use the Outside Diameter (OD) to check your pipe against fittings. Below is a quick reference for common spa & pool pipe sizes:
| Imperial Name | Metric Name | Pipe Diameter (OD) |
|---|---|---|
| 1" | 25 mm | ~33.4–33.7 mm |
| 1.5" | 40 mm | ~48.1–48.4 mm |
| 2" | 50 mm | ~60.2–60.5 mm |
| 2.5" | 65 mm | ~75.2–75.5 mm |
These are nominal sizes and are designed to fit matching fittings — not to measure exactly what their name suggests.
Understanding Plumbing Sizes & Nominal Measurements
Plumbing sizes can be confusing. PVC and many other pipe systems use nominal sizes—the size is a name, not the exact measured dimension. This convention is used across most pool and spa systems so that pipes and fittings remain compatible.
Why pipe sizes don’t match the measurements
The Nominal Pipe Size (NPS) system standardises pipe dimensions so that pipes, fittings, valves, and accessories interoperate. Plumbers work with these nominal names every day, but DIYers can be tripped up if they try to match by a tape-measure alone.
How to Measure Pipe Correctly
-
Pipe size is identified by:
- The pipe’s Outside Diameter (OD).
- The fitting’s Inside Diameter (ID) (socket opening).
- Pipe Class / Schedule (e.g., Class 9, 12, 18 or Sch 40) relates to wall thickness and therefore the Internal Diameter (ID) and pressure rating.
- The outside diameter of a fitting is not useful (wall thickness varies by manufacturer).
PVC Pressure Pipe AS/NZ 1477 Dimensions1:
Common nominal sizes with typical outside diameters and indicative inside diameters by class.
| Imperial Name | Metric Name | Outside Diameter (OD) | Class 9 IDº | Class 12 IDº | Class 18 IDº |
|---|---|---|---|---|---|
| 1/2" | 15 mm | ~21.2–21.5 mm | 18.3 mm | 17.8 mm | |
| 3/4" | 20 mm | ~26.6–26.9 mm | 23.7 mm | 22.4 mm | |
| 1" | 25 mm | ~33.4–33.7 mm | 30.5 mm | 29.8 mm | 28.1 mm |
| 32 mm | ~42.1–42.4 mm | 38.5 mm | 37.5 mm | 35.4 mm | |
| 1.5" | 40 mm | ~48.1–48.4 mm | 45.2 mm | 44.1 mm | 42.8 mm |
| 2" | 50 mm | ~60.2–60.5 mm | 55.2 mm | 53.7 mm | 50.5 mm |
| 65 mm | ~75.2–75.5 mm | 68.9 mm | 67.0 mm | 63.2 mm | |
| 2.5" | ~73 mm |
- º Internal diameters vary slightly by manufacturer and class.
- 1 Not all pool/spa fittings match these dimensions exactly. Some do not follow Australian or international standards. Chinese spas may use proprietary fittings.
Hose & Tube Dimensions
Common flexible hose sizes used in pool/spa systems (approximate IDs).
| Imperial Name | Metric Name | Inside Diameter (ID) |
|---|---|---|
| 3/8" | 9–10 mm | ~9 mm |
| 3/4" | 19 mm | ~19 mm |
BSP – British Standard Pipe Thread Sizes
BSP thread names are also nominal. The thread OD will not equal the nominal name.
| BSP Thread Size Naming | Outside Diameter (mm / inch) | TPI |
|---|---|---|
| 1/16" BSP | 7.7 mm / 0.304" | 28 |
| 1/8" BSP | 9.7 mm / 0.383" | 28 |
| 1/4" BSP | 13.16 mm / 0.518" | 19 |
| 3/8" BSP | 16.66 mm / 0.656" | 19 |
| 1/2" BSP / 15 mm | 20.99 mm / 0.825" | 14 |
| 5/8" BSP | 22.99 mm / 0.902" | 14 |
| 3/4" BSP / 20 mm | 26.44 mm / 1.041" | 14 |
| 7/8" BSP | 30.20 mm / 1.189" | 14 |
| 1" BSP / 25 mm | 33.25 mm / 1.309" | 11 |
| 1-1/4" BSP | 41.91 mm / 1.650" | 11 |
| 1-1/2" BSP / 40 mm | 47.80 mm / 1.882" | 11 |
| 2" BSP / 50 mm | 59.61 mm / 2.347" | 11 |
| 2-1/4" BSP | 65.71 mm / 2.587" | 11 |
| 2-1/2" BSP | 75.18 mm / 2.960" | 11 |
| 3" BSP | 87.88 mm / 3.460" | 11 |
| 4" BSP | 113.03 mm / 4.450" | 11 |
| 5" BSP | 138.43 mm / 5.450" | 11 |
| 6" BSP | 163.83 mm / 6.450" | 11 |
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