Aquaflo Davey LX SpaNET Whirlpool 50mm 2" Pump & Barrel Union Joiner
Aquaflo Davey LX SpaNET Whirlpool 50mm 2" Pump & Barrel Union Joiner is backordered and will ship as soon as it is back in stock.
Don't Guess - Ask Us!
Don't Guess - Ask Us!
Not sure if it’s the right part? Send us a message and a photo of what you’re replacing, or what you need, and we’ll help make sure you get the right part the first time.
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Delivery and Shipping
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Aquaflo Davey LX SpaNET Whirlpool 50mm 2" Pump & Barrel Union Joiner is backordered and will ship as soon as it is back in stock.
Genuine pump barrel union to suit a wide range of spa jet pumps using the common USA 2" FBT fine thread connection. This union is used on many Aqua-flo, Davey, Spa-Quip QB, LX Whirlpool, SpaNET Jetmaster, Waterway and similar spa pumps.
We keep these physically in stock for fast shipping or local pick-up, unlike most drop-shipping websites.
Important Thread & Pipe Size Information
This is a fine thread 2" FBT pump union designed to suit pumps with an outside thread diameter of approximately 78-79mm OD measured across the pump thread.
The tail piece suits standard 50mm pressure pipe. This is commonly referred to as a 2" / 50mm FBT spa pump union.
If your pump thread measures around 78-79mm across the outside of the thread, this is generally the correct style of union. If your pump uses a noticeably larger or coarser thread, this may not be suitable.
Suits Common Spa Pump Brands & Models
- Aqua-flo XP, XP2 and XP2e pumps
- Balboa SuperWow and Ultimax pumps
- Davey Spa-Quip QB pumps with fine thread fittings
- Davey QB pumps marked with AUS in the model number
- LX Whirlpool LP and WP series pumps
- SpaNET XS Jetmaster pump series
- Waterway Executive and Hi-Flo pumps
- Many other spa jet pumps using USA 2" FBT fine thread unions
Common Spa Brands Using This Style
This style of union is commonly found on pumps fitted to many Australian and imported spas, including selected models from:
- Arcadia spas
- O2 spas
- Monarch spas
- Vortex® spas
- Sapphire spas
- Heritage spas
- Oasis spas
- WWDG and SpaPro style imports using compatible pump fittings
Included Parts
- Union nut
- 50mm tail piece
- O-ring seal
Common Part Numbers
This style of pump barrel union may be associated with part numbers including:
- 52202000
- 400-557
- 403116
- 403117
- D7031
- 21023-000-000
Before Ordering
Please check the outside diameter of the thread on your pump before ordering. This union suits pumps with an approximate 78-79mm outside thread diameter.
If you are unsure, send us clear photos of your existing pump union and a measurement across the outside of the pump thread. Spa pump unions can look similar in photos, but coarse thread, fine thread and different barrel union sizes are not always interchangeable.
Click here for more information about 2" / 50mm FBT spa pump thread sizing.
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 | ~60.2–60.8 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.
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) |
|---|---|---|
| 1/2" | 15 mm | ~21.2–21.5 mm |
| 3/4" | 20 mm | ~26.6–26.9 mm |
| 1" | 25 mm | ~33.4–33.7 mm |
| 32 mm | ~42.1–42.4 mm | |
| 1.5" | 40 mm | ~48.1–48.4 mm |
| 2" | 50 mm | ~60.2–60.8 mm |
| 65 mm | ~75.2–75.5 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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