How to choose a shop vac (and why 'peak horsepower' tells you little)

A shop vac, or wet/dry vac, is the tool you're glad you own the first time a water heater leaks or a project fills the garage with sawdust. Choosing one is simple once you know which numbers to ignore.

Tank size: match it to the job

Tank size	Good for
2–5 gallons	Cars, small cleanups, apartments; easy to carry and store
6–12 gallons	General home and garage use; a good all-round size
12–16 gallons	Workshops, renovation cleanup, larger water jobs

Bigger tanks hold more before you empty them, which matters most for water: water is heavy, and a full 16-gallon tank is a lot to lift. That's why a drain port near the bottom is so useful on larger models.

Ignore "peak horsepower"

Many shop vacs advertise "peak HP" in large numbers. Peak horsepower is a brief figure measured under conditions that don't match real cleaning, and it's not a good way to compare models.

Two specs tell you much more:

• Airflow (CFM, cubic feet per minute): how much air moves through the hose. High airflow is good for picking up light, bulky debris like sawdust, leaves and wood chips.
• Water lift / sealed suction (in inches): how strongly the vac pulls. High water lift is good for heavy debris, gravel, and pulling water up from a carpet or out of a drain.

Not every listing gives both. When they're available, they're the most honest way to compare.

Hose diameter

Hose	Strengths
1-1/4 inch	Light, flexible, fits many power tool dust ports; can clog with larger debris
1-7/8 inch	A common middle ground for home models
2-1/2 inch	Picks up chunky debris without clogging; heavier and stiffer

A longer hose makes it easier to move around, but each extra foot reduces suction at the nozzle a little. If you plan to connect it to a sander or saw, check the hose and adapter sizes against your tools.

Filters: this is where most people go wrong

The filter decides whether fine dust ends up in the tank or blown back into the air.

• Standard cartridge filter: for general dry debris.
• Fine-dust or HEPA-rated cartridge: for drywall dust, ash and fine sanding dust. Fine dust clogs or passes through standard filters quickly.
• Disposable filter bags: catch debris before it reaches the cartridge, which keeps suction strong and makes emptying much cleaner. Worth it for dusty jobs.
• Foam sleeve: for wet pickup. Many paper cartridges must be removed for wet use unless they're rated for it; check the manual.

Always empty and dry the tank and filter after wet pickup to avoid mildew smells.

Features that make life easier

• Drain port for emptying water without lifting the whole tank.
• Blower port to blow leaves or sawdust off a deck or out of a garage.
• Onboard storage for the hose, cord and attachments.
• Tool-activated outlet on some models: plug a power tool into the vac and it starts automatically when the tool does.
• Casters and a stable base, so it doesn't tip when you pull the hose.
• Noise level: shop vacs are loud. If one lists decibels, lower is better; ear protection is sensible for long sessions.

Cordless shop vacs

Small cordless vacs that share batteries with your drill are convenient for quick cleanups and cars. They usually have smaller tanks and shorter runtimes, so they complement a corded vac more than replace one.

Questions people ask

Can I use a shop vac for drywall dust?

Yes, with a fine-dust or HEPA-rated filter and ideally a filter bag. A standard filter clogs fast and can let fine dust through.

Can I vacuum water with the regular filter in?

Check your manual. Many paper filters must be removed or replaced with a foam sleeve for wet pickup.

Why does my shop vac lose suction?

Usually a clogged filter, a full tank or bag, or a blocked hose. Clean or replace the filter first.