Astralpool / Zodiac Air Bleed Plug D-Thread & O-Ring

Astralpool / Zodiac Cartridge Filter Air Bleed Plug & O-Ring - D-Thread - 78705 / 78103

Genuine Astralpool air bleed plug (air release / bleed screw) complete with its O-ring, part numbers 78705 / 7870510 (plug) and 78103 (O-ring). It threads into the top of the filter to release trapped air on start-up. The twin-start "D" thread is designed so the plug will not pop out under pressure. Fits the entire Astralpool / Hurlcon cartridge filter range and most other filters using the same common thread.

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

The 1/4-inch BSP Thread Check

This is a common-thread part, so it fits by thread, not by filter model:

1. Look at the threaded air-bleed port on top of your filter.
2. If it is the common 1/4" BSP (~13mm) thread, this plug and O-ring fit - whatever brand the filter is.

The Zodiac ZXC is the Zodiac-badged Astralpool ZX, so ZXC filters use this plug too.

Fits Across The Astralpool / Hurlcon Range

• Astralpool / Hurlcon ZX & Zodiac ZXC / ZCF cartridge filters (ZX50 to ZX310)
• Astralpool / Hurlcon QX, CL, CF, UF, QL cartridge filters
• Astral IX / IX50 in-line leaf canisters
• WWDG and many other brands using the same 1/4" BSP air-bleed thread

Because it is a common-thread part, it also suits many filters outside the Astralpool range - confirm your port is the 1/4" BSP (~13mm) thread and it will fit.

Fitting Tip

Use a small amount of silicone lubricant on the thread to stop the plastic binding. Hand-tighten only.

Also Need The Lid Or Tank Seal?

ZX / ZXC lid assembly - SP7820502 · ZX / ZXC tank O-ring - 78110 · Full ZX / ZXC range & spare parts

Part Numbers & Search References

Plug: 78705 / 7870510 · O-ring: 78103 · Old numbers: 78205, 78207 · air bleed plug · air release valve · bleed screw · D-thread air bleed · ZX filter air bleed · Zodiac ZXC air release · 1/4 BSP cartridge filter bleed plug.

Frequently Asked Questions

Will this fit my filter?
If the air-bleed port on your filter is the common 1/4" BSP (~13mm) thread, yes. It fits the whole Astralpool / Hurlcon range and most other brands using that thread.

What is the D-thread?
A twin-start thread that stops the plug being blown out under pressure, while still letting you open it by hand to bleed air.

Does it come with the O-ring?
Yes. The plug is supplied with its sealing O-ring (part 78103).

My filter is a Zodiac ZXC. Is this the right plug?
Yes. The Zodiac ZXC is the same filter as the Astralpool ZX, just Zodiac-badged, so this plug fits.

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.