Shop-Vac 90304 Cartridge Filter 8 Inch

The Shop-Vac 90304 captures up to 95% of particles down to 5 microns — good enough for sawdust and general debris but nowhere near HEPA territory. Compatible with most Shop-Vac models 5 gallons and larger, it’s the workhorse filter that comes standard on many units. At 8 inches diameter and 6.5 inches height, it fits the filter cage without drama.

Skip this filter for drywall dust unless you’re adding a collection bag. Paper-based pleated media clogs fast with fine particles. Spring for the Ultra-Web or HEPA versions if you’re doing demolition or lead paint work.

Filtration Performance That Actually Matters

95% efficiency at 5 microns sounds impressive until you realize what it misses. Concrete dust particles run 0.1 to 3 microns. Mold spores float at 1-5 microns. This filter catches the big stuff while the small stuff — the particles that actually damage your lungs — sail right through.

Specification	Value
Filtration Efficiency	Up to 95%
Particle Size Rating	Down to 5 microns
Filter Media	Paper-based pleated filter media
Reusable	Yes (can be tapped clean or rinsed, though rinsing paper filters may shorten life)

The pleated design maximizes surface area, which helps airflow. But here’s the catch — paper media can be tapped clean or rinsed, though rinsing paper filters may shorten life. Once that paper gets saturated and dried a few times, it turns brittle. Contractors report destroying these filters by cleaning them too aggressively.

Compare this to alternatives that actually handle fine dust: Shop-Vac’s HEPA cartridge captures 99.97% of particles down to 0.3 microns. That’s the difference between filtering sawdust and filtering what actually hurts you. The Ultra-Web small cartridge offers higher efficiency for fine dust and drywall dust, plus it’s easier to clean.

Installation and Compatibility

No tools required for installation — one of the few things Shop-Vac got completely right. The process takes under a minute:

1. Unplug the vacuum and remove the motor head
2. Remove the old filter by unscrewing the retainer nut and sliding the filter off the cage
3. Slide the new cartridge filter over the filter cage until it is seated against the motor cover
4. Place the filter lid/retainer cap over the bottom of the filter
5. Tighten the retainer nut by hand until snug (no tools required)

Reviews note some users report difficulty with the retainer nut if missing. Lost that nut? Good luck finding a replacement at the local hardware store. Shop-Vac doesn’t sell them separately.

Compatibility Details
Compatible With	Most Shop-Vac brand wet/dry vacuums (5 gallons and larger)
Incompatible Models	5 Gallon Portable model H87S, 5 Gallon HangUp®, 5 Gallon Wall Mount, 6 Gallon Long Life model P12S
Physical Dimensions	8 inches diameter, 6.5 inches height

Wet/Dry Performance Reality

Supports both wet and dry pickup without filter changes — technically true but misleading. Yes, the filter handles both. No, it won’t perform well after getting soaked. Foam sleeves are preferred for liquid-only tasks because they don’t turn into soggy cardboard.

The real issue? Paper media can tear if saturated and handled roughly. Pull a wet paper filter off the cage too fast and you’ll rip it. Let it dry in place and it’ll stick to the cage. Montana’s humidity swings make this worse — a filter that gets wet in a cold shop then moves to a heated space can warp as it dries.

For contractors bouncing between water cleanup and sawdust collection, keep a foam sleeve handy. Swap filters based on the job, not Shop-Vac’s marketing claims about universal performance.

FAQ

How often should this filter be replaced? The filter is reusable and can be tapped clean or rinsed, but realistically expect 6-12 months of contractor use before the pleats clog permanently. Weekend warriors might stretch it to 2 years. Some users report the paper media can tear if saturated and handled roughly, which shortens lifespan considerably.

Can this filter handle drywall dust? Not effectively on its own. The applications list notes drywall dust only if used with a high-efficiency collection bag. Without that bag, fine drywall particles clog the pleats within minutes. The Ultra-Web filter is specifically noted as better for drywall dust and easier to clean.

What’s the warranty coverage? Limited Lifetime Home Use Warranty for the original purchaser, non-transferable. Key word: “Home Use.” Commercial contractors technically void the warranty the moment they use it on a job site. Shop-Vac knows contractors use these but won’t honor commercial claims.

Should contractors upgrade to HEPA for shop use? Depends on what you’re doing. HEPA captures 99.97% of particles down to 0.3 microns versus this filter’s 95% at 5 microns. If you’re cutting treated lumber, grinding concrete, or dealing with any toxic dust, HEPA isn’t optional. For general woodworking with untreated lumber, the standard cartridge works fine.

Why do reviews vary from 3.6 to 4.2 stars? Common positives include easy installation, perfect fit for older models, and durability for general use. Common negatives include difficulty with the retainer nut if missing and paper media tearing when wet. The variance likely reflects different use cases — homeowners doing light cleanup rate it higher than contractors pushing it hard daily.