Astralpool / Zodiac Brass Hex Nut M8 - TX / CX / CTX / E-Series 40272

Name: Astralpool / Zodiac Brass Hex Nut M8 - TX / CX / CTX / E-Series 40272
Brand: FLUIDRA
SKU: 40272
Price: 4.00 AUD
Availability: InStock

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Astralpool / Zodiac Brass Hex Nut M8 - TX / CX / CTX / E-Series 40272 is temporarily out of stock and will ship as soon as it's available.

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Astralpool / Zodiac Brass Hex Nut M8 40272

Genuine Fluidra M8 brass hex nut, part number 40272. Astralpool lists it for the TX, CX, CXE and CTX pump ranges. Sold individually.

Physically Stocked, unlike most "drop-shipping" websites.
Shipped from VIC, NSW, WA, QLD

Why Brass, Not Steel

This nut is brass rather than plated steel for a reason. It sits in the splash zone of a chlorinated or salt pool, where a zinc-plated steel nut rusts solid within a season or two and then rounds off or snaps when someone tries to undo it. Brass keeps releasing. Substituting a hardware-store steel nut is a false economy that turns the next service into a drilling job.

When To Replace

The nut is seized, furred with corrosion, or has rounded off
The thread has picked up or stripped
Reassembling a wet end and refreshing the fasteners as a set

Fitting Notes

Snug, not gorilla-tight. These clamp against moulded plastic, which crushes long before the fastener yields. Tighten opposing nuts progressively rather than fully torquing one at a time, so the plate pulls down square.

Related Fasteners & Wet End Parts

78772 — M8 x 50mm seal plate bolt with washer (buy here)
40173 — M10 x 25 hex washer head bolt (buy here)
SP40030 — seal plate, MkII (buy here)
SP40031 — volute / wet end, MkII (buy here)

Fits These Pumps

Astralpool CTX — CTX 180, 280, 360, 400, 500 (including MkII)
Hurlcon & Astralpool CX, CXE and TX ranges
Astralpool E-Series — E 140, E 170, E 230

Common search terms: Astralpool 40272, M8 brass nut, CTX pump brass nut, Astral TX CX CTX hex nut, Hurlcon pump nut.

Manufacturer Catalogues, Diagrams & Part Numbers

Need exploded views, spare part numbers, product numbers or diagrams? See the manufacturer catalogue: Astralpool Catalogue 2026 | Zodiac 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.

To the layperson, plumbing sizes and their names can be confusing due to the nominal sizes and naming conventions used.

This is not something we made up. Plumbers and manufacturers have used nominal (meaning ‘by name only’) sizing for decades.

Simply put, in plumbing, named sizes are often not the actual measurements of the pipe, fitting, or part. A PVC pipe called “50mm” or “2"” does not measure 50 mm anywhere. Instead, it follows nominal sizing, an internationally-standardised naming system.

Almost all fittings we use in the pool & spa industry use “pressure PVC” pipe & fittings. Do not confuse with “DWV” or other pipe & fittings and their names and sizes.

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

To reiterate, these are nominal sizes and are designed to fit matching fittings — not to measure what their name suggests. These are based on PVC Pressure Pipe AS/NZ 1477 Dimensions^1.

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 and other plumbing areas so that pipes and fittings remain compatible.

Quick example: A 2" / 50 mm fitting is named for the pipe it connects to, but the pipe’s actual outside diameter (OD) is approx. 60.3 mm (typically ~60.2–60.5 mm in AS/NZ pressure pipe).

Another example: a 2” / 50mm o-ring may refer to a barrel union, etc that suits 50mm pipe. Eg: a “50mm Balboa Gasket” refers to a heater gasket that measure 74mm across, but suits a Balboa barrel union made for 50mm pipe (and the 50mm pipe does not measure 50mm either!)

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).

Important: For pool/spa work, most plumbing uses Pressure Pipe (AS/NZ standards) — not DWV. Always check OD and the pipe class against your equipment specifications.

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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