Commercial Vacuum Losing Suction: How to Find and Fix the Cause

When a commercial vacuum is losing suction, the cause is almost always something blocking or leaking air: a full or clogged bag, a dirty filter, a blockage in the hose, wand or floor head, or a loose hose connection. On uprights, a broken or slipping belt stops the brush and makes the machine seem weak even when suction is fine. Bissell, which makes Sanitaire, says most suction loss comes from an obstruction in the air path, so test the airflow section by section before you suspect the motor.

Find the problem: test suction section by section

Bissell’s support advice for Sanitaire uprights starts with testing suction at the end of the hose. Work from the motor outward:

1. Remove the hose at the machine and feel the suction at the machine’s inlet. Weak here means the bag, filters or motor.
2. Reconnect the hose and feel the suction at the free end. Weak here, but strong at the inlet, means the hose is blocked or leaking.
3. Add the wand, then the floor tool, one at a time. The point where suction drops is where the blockage is.

1. The bag is full, or clogged before it is full

Bags filter air as well as hold dirt. As the pores fill, airflow drops long before the bag looks full. Fine dust such as drywall dust, toner, powder and fine sand clogs a bag far faster than normal soil.

• A common rule is to change bags at about two thirds full in normal use, and sooner with fine dust. Check your manual for its fill line.
• Use the bag type the maker specifies. A bag that does not seat in its collar leaks dust past the filter and into the motor.
• On bagless or cloth-bag machines, empty the container and clean the cloth bag regularly.

2. The filters are dirty

Commercial vacuums often have several filters: a pre-motor filter, a HEPA or exhaust filter, and on backpacks a cloth filter behind the paper bag. Any one of them clogged cuts airflow. Sanitaire’s manual for its SC5713 and SC5815 uprights says to check the filters, belt and brush roll often.

• Tap out or rinse washable filters as the manual says, and let them dry completely before refitting.
• Replace paper and HEPA filters on schedule; they cannot be washed.
• Never run without the filters. Dust reaching the motor wears it out.

Wet/dry machines have their own rule. ProTeam says that for dry pickup the dry filter must be installed, because without it fine dust reaches the motor. Using a wet-pickup setup on fine dust also clogs quickly. See our guide to what a HEPA vacuum is for when a sealed HEPA system matters.

3. The hose, wand or floor head is blocked

Blockages collect where air turns a corner: the hose cuffs, the elbow at the floor head, and the inlet of the bag compartment. Common culprits are paper, plastic wrappers, cable ties, pens, hair and wet debris that has dried into a plug.

• Look through the hose toward a light, or drop a coin through it while holding it straight.
• Push a blockage out with a broom handle from the clear end, gently, so you do not split the hose.
• On uprights, check the passage behind the brush roll where dirt enters the hose.

4. A hose or seal is leaking air

A split hose or a loose cuff lets air in before it reaches the floor, so the machine sounds normal but picks up little. Sanitaire’s manual lists “no suction at end of hose” and says to make sure the hose adapter is secure.

• Run the vacuum and bend the hose along its length, listening for a hiss.
• Check the hose cuffs, wand joints and the bag door seal.
• Replace a split hose; tape is a short-term fix at best.

5. Upright: the belt or brush roll

On uprights, much of the carpet cleaning comes from the brush roll agitating the pile. If the brush stops, pickup collapses even when suction is strong. Sanitaire lists a broken, cut, loose or stretched belt as a cause of poor cleaning.

• Turn the machine over, unplugged, and check that the belt is whole and tight.
• Cut away hair and string wrapped around the brush roll.
• Replace worn bristles or the whole brush roll when the bristles no longer reach the carpet.

Machines with a brush indicator help. Windsor’s Versamatic manual says a red light means the brush is blocked and not turning: switch off, unplug and clear the blockage.

6. The height setting is wrong

On manual-height uprights, a setting too high leaves the head above the carpet, and too low on thick carpet chokes the airflow. Set it so the brush just touches the pile. Many commercial uprights adjust automatically; if yours does not, check the setting when you move between carpet types.

7. The motor or fan

Only after all of the above. Signs of a motor or fan problem:

• A changed sound: grinding, rattling or a lower pitch.
• A burning smell.
• Weak suction at the machine inlet with a new bag and clean filters.

Some commercial uprights use a direct-air design, where dirt passes through the fan on its way to the bag. A hard object such as a screw or coin can chip the fan and reduce suction. On these machines, pick up hard objects by hand. Motor and fan repairs are usually a job for a vacuum shop.

Bags that fit our upright and backpack picks

Sanitaire uprights

Sanitaire LS premium paper bags, 5 pack (63256A)

Fits SC5713, SC5815 and SP5816 series uprights.

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ProTeam 6 qt backpacks

Aftermarket 107314 filter bags for ProTeam 6 qt backpacks, 30 pack

Aftermarket, not ProTeam branded. The listing says it fits Super Coach Pro 6, ProVac FS 6 and GoFit 6.

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As an Amazon Associate we earn from qualifying purchases. Prices and availability change, so check the current price on Amazon.

How to keep suction strong

• Change bags early, especially after fine dust.
• Clean or replace filters on a schedule, not only when suction drops.
• Check the belt and brush roll weekly on uprights in daily use.
• Pick up hard objects by hand.
• Store hoses loosely coiled so they do not kink or crack.

Choosing a new machine? See our guides to the best commercial upright vacuums and best commercial backpack vacuums.

Frequently asked questions

Bottom line: suction loss is almost always airflow: the bag, filters, a blockage or a leak. Test from the motor outward to find it, check the belt and brush on uprights, and only then suspect the motor.