Standard Flow vs High Flow: Which Attachments Need Which?

The math isn't complicated. A standard-flow skid steer running 17 GPM at 3,500 PSI produces roughly 34 HP of hydraulic power. A high-flow machine at 40 GPM and the same pressure produces over 80 HP. Double the flow, more than double the usable power at the attachment. That gap is why some tools simply don't function properly on standard-flow machines — not sluggishly, not partially, but actually don't work at designed spec.

Most Canadian operators run one of a handful of machines: Bobcat S/T/R series, Case SV series, Cat 226D/232D/262D, Kubota SSV65/75, or John Deere 317G/320G. Every one of those has both standard-flow and high-flow variants. Knowing which you have — before you buy an attachment — is step one.

How to Tell What Your Machine Has

Check the serial number plate on your machine, then look up the spec sheet on the manufacturer's site. What you want is the auxiliary hydraulic flow rating, listed in GPM (gallons per minute) or L/min. Standard-flow machines fall in the 17–25 GPM range. High-flow machines run 30–45 GPM.

Some machines have high flow as a factory option — you need to know whether your specific unit was ordered with it. A Bobcat T650, for example, offers both standard (23.6 GPM) and high-flow (36.4 GPM) configurations. Two visually identical T650s at a rental yard can have completely different hydraulic capability. Ask the dealer, pull the spec sheet, or check the cab — most machines with high flow have a dedicated high-flow circuit switch or selector.

Attachments That Run Fine on Standard Flow

These are tools with lower hydraulic demands — either they move slowly by design, or they use hydraulic power intermittently rather than continuously.

• Buckets and grapples — No hydraulic motor, just a cylinder for curl/tilt. Standard flow handles these no problem.
• Pallet forks — No hydraulic requirement beyond the machine's lift circuit.
• Augers — Most standard auger drives run at 10–20 GPM. A Bobcat auger drive or Danuser FM series runs fine on standard flow. High-torque auger drives for larger bits in hard ground start to benefit from high flow.
• Post drivers — Hydraulic hammers for fence posts typically require 10–20 GPM.
• Box blades and land planes — These use no hydraulics beyond angle adjustment cylinders.
• Vibratory plate compactors — Most compactors are designed for standard flow (15–25 GPM), though larger units push into high-flow territory.
• Backhoe attachments — Cylinder-based, low flow demand.
• Tillers — Standard gear-drive tillers run at 15–22 GPM. High-flow tillers exist but aren't required.
• Soil conditioners — Most 60–72" soil conditioner/preparator attachments are rated for 14–22 GPM.
• Sweepers/brooms — Angle brooms and pickup sweepers run hydraulic motors that typically need 15–20 GPM.

Attachments That Require High Flow

These tools have hydraulic motors that genuinely need the volume a high-flow system provides. Running them on standard flow means the motor spins slower than designed — less cutting speed, less production, more heat, and faster wear.

• Forestry mulchers (drum or disc) — No exceptions here. Denis Cimaf's DAF-180D calls for 37–52 GPM. Fecon's FTX75 drum head needs 30–45 GPM. Running either on a 20-GPM machine is not mulching — it's just noise.
• Brush cutters / forestry mowers — Dedicated forestry brush cutters for heavy material typically need 25–40 GPM.
• Cold planers / asphalt planers — Rotary drum planers (Bobcat, Wirtgen, Simex) run 30–40 GPM to spin the drum at productive RPM.
• Rock saws — High-torque sawing through rock or concrete requires 30–40 GPM.
• Stump grinders (large) — Compact stump grinders can run on standard flow, but production stump grinding heads (Fecon, Denis Cimaf) targeting 12"+ stumps at pace need high flow.
• High-production trenchers — Standard trenchers for utilities (Vermeer, Ditch Witch attachments) run 15–25 GPM. Industrial chain trenchers cutting hardpan in Manitoba or frozen ground in the Yukon push the demand up to 30+ GPM.
• Snowblowers (large) — A 72–84" single-stage snow blower moves a lot of snow; that rotor needs 25–35 GPM to throw properly. Many quality snowblowers specifically list high-flow as a requirement.

The In-Between Zone

Some attachments work on standard flow but perform noticeably better — or have specific models rated — for high flow. This middle ground trips up a lot of buyers.

The Cost of Getting It Wrong

There are two failure modes. The first is buying a high-flow-required attachment for a standard-flow machine. You'll either damage the attachment motor (they run hot when starved for flow), void the warranty, or just get 40–50% of rated production. The attachment dealer will tell you this before you buy — if you tell them your machine's GPM rating. Don't skip that step.

The second mistake is adding a high-flow kit to a machine that wasn't designed for it. High-flow hydraulics aren't just a bigger pump — they require larger reservoir capacity, upgraded coolers, and bigger lines throughout the system. Aftermarket "high-flow conversions" exist, but they vary wildly in quality. A proper conversion through the OEM or a qualified hydraulic shop costs $3,000–$8,000 CAD and is worth doing right. A cheap conversion that bypasses the cooling circuit will toast your hydraulic system on a hot July afternoon running a mulcher in Northern BC.

Common Canadian Machines and Their Flow Ratings

Note the Kubota SSV75 — no high-flow option. A common machine on Canadian acreages and small operations, and it means forestry mulchers, large cold planers, and production snowblowers simply aren't compatible. Not a knock on the machine — it's great for what it does — but knowing the limit before you buy an attachment matters.

Bottom Line

Pull your machine's spec sheet. Find the auxiliary hydraulic flow in GPM. Then check every attachment you're considering against its required GPM range. Takes five minutes. Skipping this step has cost Canadian operators thousands of dollars in returned attachments, voided warranties, and damaged hydraulic systems.

For most landscapers and property owners running standard buckets, augers, tillers, and forks — standard flow is perfectly adequate. The high-flow conversation only matters when you're adding rotary tools: mulchers, cold planers, rock saws, heavy brush cutters. Plan your attachment lineup before you spec your next machine, not after.