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Replacing Shop Vac Filter

Find the right replacement filter for your shop vac, install it in under 5 minutes, and learn the wet/dry swap most beginners get wrong.

For: Workshop owners replacing a shop vac filter for the first time — or trying to figure out which filter they actually need

24 min read11 sources7 reviewedUpdated Apr 25, 2026

Shop Vac Filter at a Glance

A shop vac filter needs replacing when suction drops and cleaning won't bring it back. Torn paper, collapsed pleats, and a burnt smell are the clear signals. Finding the right replacement takes 30 seconds: model number on the power head, then cross-reference by tank size. Installing it takes under 5 minutes with no tools.

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SHOP VAC FILTER TYPES — CHOOSE THE RIGHT ONE PAPER CARTRIDGE cage opening DRY DUST ONLY sawdust · chips · debris #90398 (≤4 gal) · #90304 (5+ gal) FOAM SLEEVE WET PICKUP ONLY water · liquid spills #90526 (≤4 gal) · #90585 (5+ gal) HEPA CARTRIDGE HEPA HEALTH-SENSITIVE DUST MDF · drywall · allergens #90341 (≤4 gal) · #90340 (5+ gal)
Three filter types, three jobs. Paper cartridge handles regular dry dust and chips. Foam sleeve protects the motor during wet pickup — never run paper cartridge for water. HEPA cartridge is required when fine particles like MDF dust or drywall are a health concern.
Most common filter typePleated paper cartridge
Replace whenTorn paper, collapsed pleats, or suction doesn't return after cleaning
Small vac filter (≤4 gal)#90398 (OEM ~$12–18, aftermarket ~$10–15)
5+ gal vac filter#90304 (OEM ~$14–18, aftermarket ~$11–16)
Wet pickup ruleRemove paper cartridge first; install foam sleeve instead
Cleaning lifespan~15–20 tapping/cleaning cycles before filter degrades

In this guide:

Part 1: Find the Right Filter for Your Vac

Show up at the hardware store with only the brand name and you'll probably come home with the wrong filter. Shop-Vac, Craftsman, Ridgid, and Vacmaster all make wet/dry vacs in multiple sizes, each needing a different filter. The right part number is already on the machine you own.

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FINDING THE RIGHT FILTER PART NUMBER WHERE TO LOOK ON YOUR VAC 1 Filter frame — part # molded on plastic rim 2 Power head label → look up model # at filter finder 3 Tank size only → use size chart (right) Start with the filter frame — the part # is usually printed there If it's worn off, check the motor housing label near the blower port SIZE REFERENCE CHART TANK SIZE CARTRIDGE FOAM SLEEVE ≤4 gal (small) #90398 #90526 5–8 gal #90304 #90585 10–14 gal #90304 #90585 16–25 gal #90304 #90585 All 5+ gallon vacs use the same cartridge and foam sleeve
Three ways to find the right part number, ranked fastest to slowest. The filter frame usually has the number molded right on it. If not, the model label on the motor housing lets you look it up. Tank size alone works as a last resort.

Step 1: Check the filter already in the machine

Before you pull the old filter, check the plastic frame. The part number is usually printed there: something like 90398 or 90304. Write it down. That number works at any retailer.

If the print has worn off, keep reading.

Step 2: Find your model number

The model number is on a label on the power head (the motor housing). Look near the blower port, on the rear cover, or at the base of the motor housing. Can't find it? Check the bottom of the tank. Some older models put the sticker there.

Once you have the model number, enter it into Shop-Vac's official filter finder. It returns the correct part number for your machine.

Step 3: Use the size chart if the label is gone

If your label is missing, tank size gets you close enough. Most wet/dry vac filters follow this pattern from the Shop-Vac filter guide:

Vac SizeCartridge FilterFoam SleeveHEPA Filter
Small (≤4 gal)#90398#90526#90341
5–8 gal#90304#90585#90340
10–14 gal#90304#90585#90340
16–25 gal#90304#90585#90340

The #90398 fits most compact Shop-Vac models: HangUp vacs, wall-mount units, and small garage vacs. If yours mounts on the wall or sits on a shelf rather than rolling on wheels, it's probably a 4-gallon or smaller unit. Start with the 90398.

OEM or aftermarket?

The Shop-Vac brand OEM filter (90398 or 90304) runs $12–18. Aftermarket options from POWERTEC and YUNGOO sell for $9–15, often two filters for that price. POWERTEC's 75083 carries a MERV 14 rating, capturing 75–85% of particles down to 0.3–1 micron.

For general woodworking — sawdust, chips, planer shavings — aftermarket filters work fine. For MDF sanding dust, drywall, or anything health-sensitive, buy a HEPA-certified filter, not just "HEPA-style." Per Engineer Fix's filter guide, certified HEPA means 99.97% capture at 0.3 microns. "HEPA-style" means nothing defined.

One thing to check with any aftermarket filter: the rubber gasket on the frame needs to seat tightly. A loose fit creates a bypass gap that lets unfiltered air around the media. Before you trust a new aftermarket filter, press it onto the cage and check for gaps with your finger.

Part 2: Replacing vs. Cleaning

A clogged filter is not always a dead filter. Suction loss usually means the pleats have filled with dust. A 60-second tap outdoors often fixes it. But some filters are genuinely done, and cleaning them again wastes time.

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REPLACE OR CLEAN? — QUICK DECISION REFERENCE REPLACE THE FILTER IF YOU SEE THIS ✕ Torn or punctured media — fine dust bypasses the filter ✕ Pleats collapsed flat — effective surface area is gone ✕ Burnt or musty smell that survives cleaning ✕ Filter got saturated with water — paper weakened ✕ Suction stays weak after thorough cleaning Hold the filter to a light source — a pinhole lets light through KEEP CLEANING IF ALL THREE ARE TRUE ✓ Paper is intact with no visible tears or pinholes ✓ Pleats have visible shape and spring back after tapping ✓ Filter has been through fewer than 15–20 cleaning cycles Tap outdoors against a trash can — rotate and hit all four sides Blow compressed air inside-out at low pressure (never outside-in) Do not wash paper cartridge filters — paper weakens when wet
Five conditions that mean the filter is done versus the three things that need to be true before it's worth cleaning again. If any replace condition is met, cleaning won't fix it.

Replace the filter if you see any of these

Torn or punctured media. A single pinhole in the paper lets fine dust bypass the filter and exhaust back into the air. You won't see the hole doing this; you'll just notice a fine grey haze near the exhaust. Hold the filter up to a window and look for light coming through.

Pleats collapsed flat. Healthy filter pleats spring back after cleaning. If they're permanently mashed together, the effective surface area is gone. Cleaning won't help.

Burnt or musty smell that survives cleaning. A musty smell after cleaning means mold in the media. A burnt smell means the paper scorched from the motor working too hard against a clogged filter. Neither recovers.

The filter got saturated with water. Paper cartridge filters don't dry out and return to form. Water weakens the media, and soaked pleats lose their structure. Replace it.

Suction stays weak after cleaning. Thorough cleaning and still noticeably less suction than a new filter means the media is spent.

Keep cleaning if

The paper is intact, the pleats have visible shape, and the filter is less than a few months old with moderate use. Woodwork Boss's cleaning guide puts the typical lifespan at 15–20 cleaning cycles before effectiveness drops.

How to clean before you replace

Take the filter outside. You're about to release a cloud of fine dust.

  1. Hold the filter by the plastic frame and tap the pleated sides firmly against the rim of a trash can.
  2. Rotate a quarter turn, repeat. Work all the way around.
  3. Tap the top and bottom. Most of the dust cake will knock loose.
  4. Optional: blow compressed air from the inside out at low pressure. Don't blast from the outside in. That drives dust deeper into the pleats.
  5. Don't use a brush. Bristles push dust into the paper instead of dislodging it.

Do not wash paper cartridge filters with water. The paper weakens when wet. If your filter is labeled "washable" or made from synthetic media, rinse it gently and air-dry completely before reinstalling. Engineer Fix's filter guide recommends a minimum 24 hours. A damp filter reinstalled immediately will cake with dry debris and block airflow within minutes.

Part 3: How to Install the New Filter

No tools required. The retainer that locks the filter in place is a wingnut or twist handle you tighten by hand.

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FILTER INSTALLATION — 4 STEPS, NO TOOLS 1 UNPLUG + SEPARATE Unplug from wall Lift power head off tank Invert so cage faces up always unplug first → 2 REMOVE OLD FILTER Unscrew wingnut retainer Slide old filter off cage Wipe cage with dry cloth twist gently if stuck → 3 INSTALL NEW FILTER Push onto cage rim-down Rim must seat flat on lid Reinstall retainer clockwise hand-tight only → 4 VERIFY THE SEAL Run finger around rim No gaps = proper seal Run vac 10 sec to confirm suction strong immediately
Four steps, no tools. The fit check in Step 4 is the one most people skip — running your finger around the filter rim catches bypass gaps before they exhaust fine dust back into your shop.

What you need

  • New cartridge filter (correct part number)
  • A dry cloth or paper towel

Installation steps

  1. Unplug the vac. Always.

  2. Remove the power head from the tank. On most shop vacs this means lifting straight up or releasing a latch. Set the tank aside.

  3. Invert the power head so the filter cage points up.

  4. Loosen the filter retainer. This is the plastic handle or wingnut sitting on top of the filter. Twist counterclockwise until it releases. Remove the retainer and set aside.

  5. Slide the old filter off the cage. It should pull straight off. If it's stuck, twist gently. Don't yank.

  6. Wipe the cage and housing. A quick pass with a dry cloth removes any dust sitting in the seating area. Debris under the filter rim causes gaps.

  7. Slide the new filter over the cage. Push it straight down until the rim seats flat against the inside of the lid. It should feel solid, not wobbly.

  8. Reinstall the retainer. Thread it clockwise and tighten by hand until snug. Overtightening cracks the plastic frame. You'll feel the resistance change when it's seated. Stop there.

  9. Fit check. Run your finger around the edge where the filter rim meets the lid. You're feeling for gaps. No gap means a proper seal. Any gap means unfiltered air bypasses the media.

  10. Reattach the power head to the tank. Plug in and run for 10 seconds. Suction should feel strong immediately.

Common installation mistakes

MistakeWhat happensFix
Wrong size filterGap in seal, dust exhausted back into airUse part number from old filter or size chart
Filter not seated flatWobbly in cage, poor sealPush down until rim contacts lid evenly
Retainer overtightenedCracked frame, permanent bypass gapHand-tight only — stop when you feel resistance
Skipped the fit checkBypass gap you didn't noticeAlways run your finger around the rim after install

Part 4: Wet and Dry Pickup

Paper cartridge filters and water don't mix. Most beginners learn this the hard way.

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WET vs. DRY PICKUP — USING THE RIGHT FILTER DRY PICKUP sawdust · chips · debris · drywall dust cage opening PAPER CARTRIDGE Captures fine dust down to 0.3–1 micron Part #90398 (≤4 gal) or #90304 (5+ gal) ⚠ NEVER vacuum water with paper cartridge WET PICKUP water · spills · liquid cleanup FOAM SLEEVE Open-cell foam — water passes through freely Part #90526 (≤4 gal) or #90585 (5+ gal) ⚠ NEVER use foam sleeve for fine dry dust
The swap takes 30 seconds. Paper cartridge stays in for all dry work. The moment there's water involved, remove the paper cartridge and install the foam sleeve. Running a paper filter on wet pickup will clog it immediately and risk motor burnout.

The rule: remove the cartridge, install the foam sleeve

A paper cartridge filter saturated with even a small amount of water clogs instantly. The motor strains to pull air through soaked paper, and thermal protection usually shuts the vac down within a minute. Vacmaster's filter maintenance guide puts it plainly: running a dry cartridge filter for wet pickup risks motor burnout. The filter is ruined either way.

The foam sleeve (part #90526 for small vacs, #90585 for 5+ gallon) replaces the cartridge for wet pickup. Foam is open-cell. Water passes through without clogging it, protecting the motor without restricting airflow.

The swap takes 30 seconds:

  1. Unplug the vac.
  2. Remove the power head and the cartridge filter. Store the cartridge somewhere dry.
  3. Slide the foam sleeve over the cage.
  4. Reattach the power head and vacuum.
  5. After wet use, remove the foam sleeve, rinse it with clean water, and let it air-dry completely before the next use.
  6. Reinstall the cartridge filter for dry use.

Do NOT use the foam sleeve for fine dry dust

The foam sleeve filters large debris only. For sawdust, drywall dust, or anything finer than coarse chips, the foam passes it straight through and exhausts it into your shop. Use the paper cartridge (or HEPA cartridge) for all dry pickup.

The "just a small spill" problem

Even a few ounces of liquid damages a paper cartridge. Dry pickup uses the cartridge. Wet pickup uses the foam sleeve. Judging by how much water you're vacuuming is exactly how you ruin a $15 filter.

Part 5: Extending Filter Life

Two habits triple the time between replacements: tap the filter outdoors after every session and add a collection bag inside the tank. The rest are optional upgrades.

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EXTENDING FILTER LIFE — 4 STRATEGIES TAP AFTER EVERY USE Effectiveness: 8/10 Tap outdoors on trash can 60 sec before hanging up Knocks loose fresh dust cake Prevents pleats from clogging Cost: $0 · Time: 60 seconds Extends filter by weeks per cycle USE A COLLECTION BAG Effectiveness: 9/10 Bag inside tank catches debris Before it reaches the filter Fine-dust bags for sanding work Extends cartridge life 3–5× Cost: $5–8 per bag Cheaper than early replacement ADD CYCLONE SEPARATOR Effectiveness: 10/10 Inline cyclone pre-separator Spins debris into separate bin Cuts filter replacements 5–10× Tank stays nearly clean Cost: ~$50 (Dust Deputy) Best upgrade for heavy shop use KEEP A SPARE ON SHELF Effectiveness: 5/10 (backup) One spare filter on the shelf Blown filter mid-project = stop Buy two when you buy one No scramble to the hardware store Cost: $10–15 Peace of mind on project days
Start with the two free strategies — tap after every use and add a collection bag. The cyclone separator is the best investment for heavy shop use, cutting filter replacement frequency by 5–10×.

Tap it after every use

Before you hang the vac back up, take the filter outside and tap it against a trash can for 60 seconds. Knocking loose fresh dust before it cakes into the pleats adds weeks to the filter's life. Faster than washing the hose.

Use a collection bag inside the tank

A cloth or paper collection bag inside the tank catches most of the debris before it reaches the cartridge. Vacmaster's bag lineup includes both standard and fine-dust versions. For sanding and drywall work, fine-dust bags extend cartridge life by 3–5x. At $5–8 each, they cost less than replacing a cartridge early.

Add a dust separator

A cyclone separator (like the Oneida Dust Deputy, roughly $50) connects inline between the hose and the vac. Centrifugal force spins most debris into a separate container before anything reaches the filter. The vac's tank stays nearly clean. The filter rarely needs replacing.

RELATED: Cyclone Dust Collectors A cyclone pre-separator attached to your shop vac cuts filter replacement frequency by 5–10x.

Keep a spare filter on the shelf

A blown filter mid-project stops work until you can get to the store. A spare cartridge costs $10–15. Buy two when you buy one.

Sources

This guide draws on manufacturer filter documentation, product specifications, and independent filter maintenance guides from woodworking and vacuum specialty sites.

Tools Used

Shop Vac

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