Astralpool / Zodiac Joiner ZX 310 Element Coupler 78078
Astralpool / Zodiac Joiner ZX 310 Element Coupler 78078 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 / Zodiac Joiner ZX 310 Element Coupler 78078
Astralpool / Zodiac Joiner ZX 310 Element Coupler 78078 is temporarily out of stock and will ship as soon as it's available.
Astralpool ZX 310 / Zodiac ZXC 310 Cartridge Element Coupler (Joiner) — 78078
Genuine Astralpool element coupler, part number 78078. It joins the two cartridge elements end-to-end inside the twin-element ZX 310 filter. This is a ZX 310 only part — the single-element ZX filters (50 to 250) do not use a coupler.
- Physically Stocked, unlike most "drop-shipping" websites.
- Shipped from VIC, NSW, WA, QLD
The ZX 310 is the same twin-element filter whether it is badged Astralpool ZX 310, Hurlcon ZX 310 or Zodiac ZXC 310. The Zodiac ZXC is simply the Zodiac-badged Astralpool ZX.
ZX 310 Only — Check Before Ordering
This part fits one filter: the twin-element ZX 310 (Zodiac ZXC 310). Open your filter — if you find two elements stacked end-to-end, the coupler sits between them and this is your part. If your filter has a single element, it does not take a coupler and this is not the right part.
Goes With
- ZX310 cartridge elements — 78088 (supplied as a pair)
- ZX310 tank body — 7821702
- ZX / ZXC lid assembly — SP7820502
Will Not Fit
- ZX50 to ZX250 (single element) — these run one element with no coupler.
- Astralpool XC — a separate, unrelated filter series. Contact us with your model and a photo.
Part Numbers & Search References
78078 · SP78078 · Joiner ZX 310 Element Coupler · ZX310 element joiner · Zodiac ZXC310 cartridge coupler · Hurlcon ZX310 element connector · twin cartridge filter joiner.
Frequently Asked Questions
Which filter uses this coupler?
Only the twin-element ZX 310 (Zodiac ZXC 310), which runs two 78088 elements joined by this part.
My ZX filter has a single element. Do I need this?
No. The single-element ZX filters (50 to 250) do not use a coupler.
My filter is a Zodiac ZXC 310. Is this the right coupler?
Yes. The Zodiac ZXC 310 is the same filter as the Astralpool ZX 310, just Zodiac-badged, so this coupler 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 |
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.
78078