Astralpool / Hurlcon O-Ring, Multiport Valve to Tank Body - RX180, RX280, RX320, RX360, RX400, RX500 - 75058

Name: Astralpool / Hurlcon O-Ring, Multiport Valve to Tank Body - RX180, RX280, RX320, RX360, RX400, RX500 - 75058
Brand: Astralpool
SKU: 75058
Price: 28.00 AUD
Availability: InStock

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Astralpool / Hurlcon O-Ring, Multiport Valve to Tank Body - RX Sand Filters - 75058

We keep these physically in stock for fast shipping or local pick-up, unlike most drop-shipping websites.
Shipped from VIC, NSW, WA, QLD

Genuine Astralpool 75058 O-ring, item 10 on the RX multiport valve diagram. It sits between the base of the multiport valve and the neck of the filter tank, and is compressed by the V clamp set when the valve is bolted down. This is the seal that fails when water weeps from the joint where the valve meets the tank.

Which Filters This Suits

Astralpool / Hurlcon RX sand filters: RX180, RX280, RX320, RX360, RX400 and RX500.
The same O-ring is supplied with the complete 40mm valve 76032 and the complete 50mm valve 76033.
Other Astralpool filter families use a different seal. The ECA550 and ECA650 use 7201750057.

If you are not certain, send us photos of your existing valve and the filter model label and we will confirm which one you need.

When to Replace It

Water weeping or dripping from the join between the multiport valve and the tank.
The O-ring has gone flat, hard, or has splits or nicks in it.
Any time the multiport valve is removed from the tank, as a matter of course.

Always shut the pump down and release filter pressure before removing the V clamp set and lifting the valve off the tank.

Specifications

Part number: 75058
Diagram reference: item 10, RX multiport valve
Position: multiport valve to filter tank body
Filter family: Astralpool / Hurlcon RX sand filters
Brand: Astralpool / Hurlcon (Fluidra)
Barcode: 9343609060411

Related RX Multiport Valve Parts

Frequently Asked Questions

Where does the 75058 O-ring sit?
Between the bottom of the multiport valve and the neck of the filter tank. It is item 10 on the RX parts diagram, directly above the tank and below the valve.

Water is leaking where the valve meets the tank. Is this the part?
Usually yes. A flat, split or perished tank body O-ring is the normal cause of a weep at that joint. Check the V clamp set and its bolt at the same time, because a distorted clamp or a loose bolt will let a good O-ring leak.

Does this suit a CA, ECA, EC or Cantabric filter?
No. Those ranges use different seals. Confirm the filter family on the tank label before ordering.

Should I replace it whenever I open the filter?
It is good practice. The O-ring takes a compression set once it has been clamped down, and refitting a used one is a common cause of a leak straight after a media change.

Manufacturer Catalogues, Diagrams & Part Numbers: Need exploded views, spare part numbers, product numbers, diagrams, or more product information? See the manufacturer catalogues below.

Astralpool Catalogue 2026 | Zodiac Catalogue 2026

Important Before Ordering: Please ensure you order correctly. Confirm this product is suitable before ordering. Use the catalogues above, seek professional assistance, or contact us with photos of your existing part, model details, serial numbers, and any labels.

As with all products, these must be diagnosed and fitted by a qualified and experienced person.

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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