Melt Blown Sediment Drinking Water Cartridge 5 Micron - 20" x 4.5" Big Blue - MB4520-5

Melt Blown Sediment Drinking Water Cartridge — 5 Micron — 20" x 4.5" Big Blue

A 5 micron melt blown sediment drinking water cartridge in the 20" x 4.5" Big Blue size — 508mm long, 114mm outside diameter. Model MB4520-5, HASP part number FC-MB4520-5. It drops straight into any housing built for a standard 4½" x 20" cartridge.

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

Price is for one cartridge.

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Dimensions

Length	508mm (nominal 20")
Outside diameter	114mm (nominal 4.5")
Trade size	20" x 4.5" Big Blue (also written 4½" x 20")
Media	Melt Blown Sediment
Micron rating	5 micron nominal
End style	Open double ended (DOE), no gaskets
Model	MB4520-5

Cartridge lengths are nominal industry-wide. A 10 inch cartridge measures 248–254mm and a 20 inch measures 500–508mm; the housing spring takes up the difference. Diameter has no such slack — if the diameter is wrong, the cartridge is wrong.

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Systems this suits

These are industry-standard 4½" x 20" cartridges. They fit any housing built to that size, regardless of who badged it. Known-good systems include:

• Puretec — WH Series whole-house mains (WH1-30, WH1-60, WH2-30, WH2-55, WH2-60), Ecotrol EM Series rainwater (EM1, EM2-65, EM2-75, EM2-80), Hybrid-E rainwater and UV systems (Hybrid-E6, Hybrid-E7, Hybrid-E7AMC, Hybrid-E13), FilterWall F Series. Puretec call the 4.5 inch format MaxiPlus, so a MaxiPlus 20 housing takes this cartridge
• Pentair / Pentek — Big Blue 20 inch housings, 3/4 inch and 1 inch FNPT
• Generic and house-brand housings — clear or blue sump, screw-off canister with a pressure-relief button on the cap. Single, twin and triple manifolds, caravan and RV point-of-entry filters, tank pre-filters ahead of a UV steriliser, and RO pre-filter stages.

What it will not fit. Puretec Z Series systems take Quick Twist cartridges — a sealed encapsulated format, not a loose cartridge in a sump, so nothing on this page suits them. Nor do inline push-fit cartridges (Puretec IL series and similar). And if your housing seals the cartridge on a central 222 or 226 O-ring stem, or on a knife edge, it takes a different cartridge type entirely. Open the sump and look before ordering.

Best suited to: Rainwater tanks, bores, dams and mains water. This is the standard first-stage sediment cartridge — the one that protects everything downstream of it, including UV steriliser quartz sleeves, carbon cartridges, RO membranes, solenoids and tap cartridges.

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Cross-reference — alternative part numbers

Same size, same media, same duty. Match on size first, micron second — micron ratings are nominal and each manufacturer measures them slightly differently.

Brand	Equivalent part number
HASP (this listing)	FC-MB4520-5 — model MB4520-5
Puretec PX Series (polyspun graded-density sediment)	PX05MP2

Pentek / Pentair P Series spun polypropylene in the 2.5 inch sizes, and the DGD and GD dual-gradient cartridges in Big Blue (DGD-2501-20, DGD-5005-20 / 155358-43, DGD-7525-20 / 155356-43, GD-5010-20BB / 555469-43, GD-7520-20BB / 555470-43). Note the DGD and GD cartridges are dual-rated (a coarse outer wrap over a finer core), so they are equivalent in duty and fit but not in single micron rating.

The same cartridge is sold under a long list of house brands and importer labels — Aquastream, Aqua Filter, Clarence, Filter Systems Australia, Waterpro, WECO, SpiroPure, Geekpure and others. If a competitor's part number is not listed here, give us the two measurements and the media type and we will tell you whether this is the same cartridge.

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The Two-Number Housing Rule (rev. TNH-1.0)

A drinking water cartridge is named by two numbers and only two: length and outside diameter. Get both right and it fits. The micron rating never changes the fit — that is a separate choice.

1. Shut the isolating tap, press the pressure-relief button on the housing cap, then unscrew the sump.
2. Pull the old cartridge out and measure it end to end. Roughly 248mm is a 10 inch. Roughly 508mm is a 20 inch.
3. Measure the outside diameter across the end cap. 63–70mm is a slimline (nominal 2.5 inch). 114mm is a Big Blue (nominal 4.5 inch).
4. Those two numbers name the cartridge. This one is 20" x 4.5" Big Blue — 508mm long, 114mm outside diameter.

Worked example. A Big Blue housing on the fill manifold for a WWDG swim spa at Officer, VIC. Through the blue sump it looks like a tall slimline. The vernier across the end cap reads 113.6mm and the tape reads 507mm, so it is 20 inch x 4.5 inch — a Big Blue 20. A slimline cartridge dropped into that housing leaves a 25mm annular gap all the way around and filters almost nothing.

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If yours measures something else

Same media, same 5 micron rating, in all four housing sizes:

If the old cartridge measures	Size	Part
248mm long x 63–70mm dia	10" x 2.5" Slimline	MB2510-5 — $7
508mm long x 63–70mm dia	20" x 2.5" Slimline	MB2520-5 — $17
248mm long x 114mm dia	10" x 4.5" Big Blue	MB4510-5 — $37
508mm long x 114mm dia	20" x 4.5" Big Blue	This listing

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Choosing the micron rating

The general-purpose rating. Mains water and reasonably clean tank water.

Other ratings in this cartridge, same 20" x 4.5" Big Blue size:

• 1 micron — MB4520-1 — Fine silt and cyst-size particles. The usual choice as a final polish, or ahead of a UV steriliser that needs clear water to work.
• 5 micron — this listing. The general-purpose rating. Mains water and reasonably clean tank water.
• 20 micron — MB4520-20 — Visible grit and sand. A good first stage on tank or bore water.
• 50 micron — MB4520-50 — Coarse pre-filter. Its job is to protect a finer cartridge downstream on dirty bore or dam water.

Lower number means a finer filter, not a better one. A 1 micron cartridge on dirty bore water blocks in a fortnight; a 50 micron on clean mains water barely earns its keep. Where the water is genuinely dirty, run a coarse cartridge in the first housing and a fine one in the second.

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What melt blown sediment media does

Spun polypropylene depth media, graded so the outer layers catch coarse particles and the core catches the fine ones. The cheapest way to get sediment out of a water line.

What it will not do

• It does nothing for chlorine, taste or odour. For that, use a carbon block cartridge in the same housing — CB4520-10.
• It is not washable. Once it loads up it gets replaced — rinsing a melt blown cartridge just drives the trapped silt deeper into the core.

All four media in this range share the same 20" x 4.5" Big Blue housing, so you can change what a housing does just by changing the cartridge in it: melt blown sediment, pleated sediment, carbon block or pleated carbon.

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Why a spa parts company stocks drinking water cartridges

Fill water is the one thing about a spa you get to choose completely, and it is the cheapest point in the whole system to fix. Sediment carried in on the fill hose scours pump seals and packs itself around a heater element, where it insulates the element and shortens its life. Chlorine and chloramine already present in mains water start consuming your sanitiser budget from the first fill and skew every test result you take in the opening week.

A cartridge on the fill line or the house main means a WWDG, SpaPro, Sapphire, Alpine or Vortex spa starts on water you have actually chosen, not whatever the street main happened to be carrying that morning. The same applies to pool top-up over summer, when a pool can take in more water in a fortnight than a spa holds outright.

These are plumbing-line drinking water cartridges, not spa or pool filter elements. If you are after the pleated element that sits inside a spa or pool filter body, that is a different part — see our pool and spa cartridge filters.

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When to replace it

• On pressure, not on looks. A sediment cartridge is finished when flow at the tap drops off, regardless of how clean the outside still appears. Surface discolouration is cosmetic; the loading that matters happens inside the media.
• Six months is the usual outside limit on mains water, and considerably less on tank, bore or dam water.
• Write the date on the housing in permanent marker when you fit it. Everyone believes they will remember. Nobody does.

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Also sold as / common search terms

FC-MB4520-5, model MB4520-5, Puretec PX05MP2 equivalent, polyspun, spun poly, depth sediment. Also searched as 20 inch x 4.5 inch drinking water cartridge, big blue water filter cartridge, 20 inch water filter, whole house water filter cartridge, under sink drinking water cartridge, melt blown sediment cartridge 5 micron, big blue replacement cartridge.