Astralpool Volute (Wet End) & Basket - CTX Series 1 4007502
Astralpool Volute (Wet End) & Basket - CTX Series 1 4007502 is temporarily out of stock and will ship as soon as it's available.
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.
Delivery and Shipping Info*
Delivery and Shipping Info*
Free Shipping over $99 for most products. Choose Express Post for fastest shipping!
Astralpool Volute (Wet End) & Basket - CTX Series 1 4007502
Astralpool Volute (Wet End) & Basket - CTX Series 1 4007502 is temporarily out of stock and will ship as soon as it's available.
Astralpool Volute (Wet End) & Basket - CTX Series 1 4007502
This is the genuine Astralpool Series 1 volute, part number 4007502, supplied with the basket. The volute is the main pump body (wet end) that houses the impeller, diffuser and basket. This is the original, old-style volute used on CTX and TX/CX/E pumps built before August 2014.
- Physically Stocked, unlike most "drop-shipping" websites.
- Shipped from VIC, NSW, WA, QLD
Three Generations — Order the Right One
Astralpool changed the CTX wet end twice. The volute and its matching seal plate must come from the same generation as your pump, or they will not bolt up and seal correctly. Identify your pump's era before ordering:
| Generation | Volute (wet end) | Seal plate |
|---|---|---|
| Series 1 — old style, pre-Aug 2014 | 4007502 — this product | 4009002 |
| Series 2 — Aug 2014 to 2018 | 40097 | 40098 |
| MkII — Nov 2020 onwards | SP40031 | SP40030 |
If you are not sure which generation your pump is, send us a photo of the pump and its data plate and we will identify it. This is an expensive part to order wrongly.
What the Volute Is
The volute is the moulded pump body that the motor bolts onto. It holds the basket, the diffuser and the impeller, and forms the pressure chamber that converts the impeller's spin into water flow. It is replaced when the body is cracked, when a union or port thread has failed, or when the internal sealing faces are damaged beyond what a new seal plate and o-rings will fix.
Related Series 1 Parts
- 4009002 — seal plate, Series 1 old style (black)
- 70004 — square seal plate o-ring, old style EPDM (buy here)
- 75508 / PS3868 — mechanical seal, BX / TX / CX / E / CTX (buy here)
- 40065 — basket (buy here)
- 40089 — lid complete with o-ring (buy here)
- 70006 — lid o-ring (buy here)
- Impeller — sized to your CTX model, see the CTX impeller range
Frequently Asked Questions
How do I know if my pump is Series 1?
Series 1 pumps were built before August 2014. If your pump predates that, or the old seal plate is marked 4009002, you are on Series 1 and this is the correct volute. If unsure, send us a photo of the data plate.
Can I fit a Series 2 or MkII volute to a Series 1 pump?
The generations are not cross-compatible as a mix. The volute, seal plate and their o-rings changed together. Match the whole wet end to one generation.
Does it come with the basket?
Yes, this part is supplied with the basket.
Is this a genuine Astralpool part?
Yes. We are an authorised Astralpool and Fluidra dealer and warranty agent.
Manufacturer Catalogues, Diagrams & Part Numbers
Need exploded views, spare part numbers, product numbers or diagrams? See the manufacturer catalogue: Astralpool Catalogue 2026
Before ordering: confirm this part is correct for your pump. Use the catalogue above, seek professional assistance, or contact us with photos of your existing part, model details, serial numbers and any labels. As with all products, this must be diagnosed and fitted by a qualified and experienced person. This is a special-order item.
Common search terms: Astralpool 4007502, CTX volute Series 1, CTX wet end old style, Astral Hurlcon CTX pump body, pre-2014 CTX volute.
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 |
Payment & Security
We accept: Visa, Mastercard, Amex, Apple Pay, Google Pay, ShopPay, Paypal, Zip, Afterpay
Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.
4007502