Astralpool / Hurlcon 40mm O-ring - HX, JX, 40mm MPV
Astralpool / Hurlcon 40mm O-ring - HX, JX, 40mm MPV is backordered and will ship as soon as it is back in stock.
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Don't Guess - Ask Us!
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Delivery and Shipping Info*
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Astralpool / Hurlcon 40mm O-ring - HX, JX, 40mm MPV
Astralpool / Hurlcon 40mm O-ring - HX, JX, 40mm MPV is backordered and will ship as soon as it is back in stock.
Astralpool
Genuine AstralPool / Hurlcon 40mm union O-ring, part number 75109. Commonly used on the inlet and outlet unions of selected AstralPool and Hurlcon gas pool and spa heaters, including HX and JX series heaters.
We keep these physically in stock for fast shipping or local pick-up, unlike most drop-shipping websites.
Suits selected AstralPool / Hurlcon heaters
- Hurlcon / AstralPool HX 70 gas heater
- Hurlcon / AstralPool HX 120 gas heater
- Hurlcon / AstralPool HX 150 gas heater
- Hurlcon / AstralPool JX 130 gas heater
- Hurlcon / AstralPool JX 160 gas heater
Also used on selected 40mm AstralPool / Hurlcon applications
- 40mm barrel unions
- 40mm union fittings on selected AstralPool / Hurlcon equipment
- Selected E-Series sand / media filter unions
- Some FG Fibreglass, RX and E-Series media filter 40mm union applications
- Some older Hurlcon / AstralPool 40mm multiport valve union applications
Please check the part number and measurements before ordering. AstralPool and Hurlcon used several similar-looking O-rings across heaters, filters, unions and multiport valves, so matching by size alone is not always enough.
Approximate measurements
- Outside diameter: approx. 66mm
- Inside diameter: approx. 58mm
- O-ring thickness / cross-section: approx. 4mm
Common search terms
AstralPool 75109 O-ring, Hurlcon 75109 O ring, HX 70 union O-ring, HX 120 union O-ring, HX 150 union O-ring, JX 130 union O-ring, JX 160 union O-ring, Astral 40mm union O-ring, Hurlcon 40mm union O-ring, E-Series filter O-ring, AstralPool heater union seal.
Related spare parts
HX Heater Spare Parts
JX Heater Spare Parts
Genuine part number: 75109
Manufacturer Catalogues, Diagrams & Part Numbers
Need exploded views, spare part numbers, product numbers, diagrams, or more product information? See the manufacturer catalogues: AstralPool Catalogue 2026 | Zodiac Catalogue 2026
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) |
|---|---|---|
| 1/2" | 15mm | ~21.2–21.5 mm |
| 3/4" | 20mm | ~26.6–26.9 mm |
| 1" | 25 mm | ~33.4–33.7 mm |
| 1.5" | 40 mm | ~48.1–48.4 mm |
| 2" | 50 mm | ~60.2–60.8 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. These are based on PVC Pressure Pipe AS/NZ 1477 Dimensions1.
- 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.
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).
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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75109