Astralpool / Zodiac Spigot-Zx Filter Element Lid
Astralpool / Zodiac Spigot-Zx Filter Element Lid 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.
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Delivery and Shipping Info*
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Astralpool / Zodiac Spigot-Zx Filter Element Lid
Astralpool / Zodiac Spigot-Zx Filter Element Lid is temporarily out of stock and will ship as soon as it's available.
Astralpool ZX / Zodiac ZXC Cartridge Element Locating Spigot (Plug) — 78203
Genuine Astralpool / Fluidra element locating spigot (locating plug), part number 78203. It centres and locates the cartridge element under the filter lid on the taller ZX filters, keeping the element seated square so water cannot bypass it. Supplied on its own.
- Physically Stocked, unlike most "drop-shipping" websites.
- Shipped from VIC, NSW, WA, QLD
The Zodiac ZXC is simply the Zodiac-badged Astralpool ZX, so this spigot suits both.
Which Filters Use It?
The locating spigot is fitted to the taller cartridge filters where the element needs positive location under the lid:
- Astralpool ZX 250 / Zodiac ZXC 250
- Astralpool ZX 310 / Zodiac ZXC 310
- Other taller Astral / Hurlcon cartridge filters using the same lid and element arrangement
The shorter single-element ZX filters (50 to 200) generally do not use a separate locating spigot. If you are unsure, send us a photo of your filter with the lid off.
Goes With
- ZX310 element coupler — 78078
- ZX310 tank body — 7821702 · ZX200/250 tank body — 7821302
- ZX / ZXC lid assembly — SP7820502
Will Not Fit
- Astralpool XC — a separate, unrelated filter series. Contact us with your model and a photo.
Part Numbers & Search References
78203 · SP78203 · Spigot ZX Filter Element Lid · ZX locating plug · ZX element spigot · Zodiac ZXC element locator · Hurlcon ZX250 ZX310 spigot.
Frequently Asked Questions
Which filters use this spigot?
Mainly the taller cartridge filters — the ZX 250 and ZX 310 (Zodiac ZXC 250 / 310) and similar Astral / Hurlcon models where the element locates under the lid.
My filter is a Zodiac ZXC. Is this the right part?
Yes. The Zodiac ZXC is the same filter as the Astralpool ZX, just Zodiac-badged, so this spigot fits.
My filter is an Astralpool XC. Is this the right part?
No. The XC is a separate, unrelated filter series. Contact us with your model and a photo and we will match the correct part.
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
As with all products, these must be diagnosed and fitted by a qualified and experienced person. This is a special-order item.
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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78203