Hydrovac Truck Sizing Guide: How to Choose the Right Size

Quick Answer: Choose hydrovac size by job type: 4-6 yard debris tanks for potholing and tight access, 8-10 yards for general utility work, 12 yards for production excavation, 15+ yards for remote sites with long haul times. Vacuum power should be 3,000-5,000+ CFM for most work. Water tanks of 1,000-1,200 gallons handle typical jobs without constant refills.

"What size hydrovac do I need?"

Contractors ask me this all the time. And my answer is always the same: it depends on what you're doing, where you're doing it, and how often you're doing it.

Buy too small, and you'll spend half your time dumping debris and refilling water. Buy too big, and you're burning extra fuel, paying more insurance, fighting weight limits, and struggling to fit on tight job sites.

I've worked on hydrovacs from compact 6-yard units to monster 15-yard rigs. After 25 years, I know what works for different applications. Here's how to figure out what size is right for you.

The Three Numbers That Matter

When sizing a hydrovac, three specs determine what the truck can do:

1. Debris Tank Capacity (cubic yards): How much material you can excavate before dumping.

2. Vacuum Power (CFM): How fast you can move material — measured in cubic feet per minute.

3. Water Tank Capacity (gallons): How long you can operate before refilling.

Everything else — boom reach, water pressure, chassis — matters too, but these three numbers are your starting point.

Debris Tank Capacity: How Much Can You Hold?

The debris tank is where excavated material goes. Size matters because every dump trip costs time and money.

Tank Size Categories

What Tank Size Do You Need?

Think about your typical job:

Potholing and utility verification (small holes, multiple locations): You're digging 2-3 foot diameter holes, maybe 4-6 feet deep. That's about 0.5-1 cubic yard per hole. An 8-yard tank gets you 8-16 holes before dumping. A 6-yard compact works if you're near disposal. A 12-yard is overkill.

Slot trenching and daylighting utilities (longer excavations): A 100-foot trench that's 1 foot wide and 4 feet deep is about 15 cubic yards. Even a 12-yard tank means two dumps per trench. Factor dump time into your bids.

Full excavation work (digging large areas): Production work needs production capacity. 12-15 yard tanks minimize downtime. Smaller tanks kill productivity.

Remote locations: Long hauls to disposal sites favor bigger tanks. If it's an hour to the dump site, you don't want to go every two hours. A big tank might mean one trip at the end of the day instead of three during the day.

Weight Considerations

Here's what people forget: a full debris tank is heavy.

Approximate debris weights:

A 12-yard tank of wet clay weighs 36,000-42,000 pounds. Add the truck itself (15,000-20,000 lbs empty), water tank, fuel, and you're looking at 60,000-70,000 pounds gross vehicle weight.

Road weight limits:

• Federal interstate limit: 80,000 lbs (with proper axle distribution)
• Many state and local roads: 40,000-60,000 lbs
• Residential streets: Often much lower

What this means: Bigger isn't always better. A 15-yard tank you can never fill legally is a waste. Know your routes and local weight restrictions before buying. Overweight trucks also create safety risks and can affect your CDL requirements.

Vacuum Power (CFM): How Fast Can You Move Material?

CFM (cubic feet per minute) measures how much air the blower moves. More CFM = more suction = faster material movement.

CFM Categories

What CFM Do You Need?

Material type matters:

Light, dry soil moves easily — you don't need maximum CFM.

Heavy, wet clay requires more suction. If your jobs involve saturated soil or dense material, don't skimp on CFM.

Rocks and debris need high airflow to stay suspended in the vacuum stream.

Distance matters:

The further you are from the tank (longer vacuum hose runs), the more CFM you lose to friction. Jobs requiring 20-30 foot hose runs need more power than close-up work.

My recommendation:

For general utility work, 4,000-5,000 CFM handles most conditions well. Go higher (5,500+) if you're regularly in heavy clay or saturated conditions. Going lower saves some fuel but costs productivity.

The CFM-to-Tank Size Relationship

Higher CFM fills tanks faster. Make sure they're matched:

A 15-yard tank with a 3,000 CFM blower is a mismatch — you'll wait forever to fill it. A 6-yard tank with 6,000 CFM will fill so fast you're constantly dumping.

For blower maintenance and issues, see our blower maintenance guide and vacuum troubleshooting guide.

Water Tank Capacity: How Long Can You Work?

Water does the actual excavation — the vacuum just removes the slurry. Run out of water and you're stopped.

Water Tank Sizes

*Operating time varies widely based on soil conditions, pressure settings, and operator technique.

Water Consumption Factors

Flow rate setting: Most systems run 5-10 GPM. Higher flow cuts faster but uses more water.

Soil conditions:

• Sandy soil: Lower water use, breaks up easily
• Clay: Higher water use, needs more saturation
• Frozen ground: Much higher water use (with hot water systems)

Operator technique: Experienced operators use water efficiently. New operators tend to use more.

Refilling Options

Water tank size matters less if you can refill easily:

Hydrant access: If you're near hydrants (urban work), a smaller tank works — fill as needed.

Water truck support: For remote jobs, a support vehicle can resupply water.

On-site water source: Some jobs have water access you can tap into.

No nearby water: Remote locations with no water access need maximum tank capacity or plan for water hauling.

Matching Water to Debris Capacity

Here's a rough rule of thumb: You want enough water to fill the debris tank at least once, preferably twice, before needing a water refill.

For water system issues, see our water pressure troubleshooting guide.

Other Specs That Matter

Beyond the big three, consider:

Water Pressure (PSI)

Most hydrovacs operate at 2,000-3,000 PSI. Some go higher (4,000+).

When higher pressure helps:

• Heavy clay excavation
• Frozen ground (with hot water)
• Hard-packed soil
• Cutting through roots

When standard pressure is fine:

• Sandy or loamy soil
• General utility work
• Potholing in normal conditions

Higher pressure systems cost more and require more maintenance. Don't overspend for pressure you won't use.

Boom Reach

Boom specifications:

When reach matters:

• Working over obstacles
• Reaching across traffic lanes
• Accessing areas where the truck can't get close

For most utility work, 18-22 feet of reach handles the job. Longer reach adds cost and complexity. For boom issues, see our boom troubleshooting guide.

Chassis and Engine

Chassis selection affects:

• Gross vehicle weight rating
• Maneuverability
• Driver comfort
• Resale value

Engine power: Most hydrovacs run 350-500 HP diesel engines. Match engine power to equipment demands:

Underpowered engines bog down during heavy excavation, reducing productivity and increasing fuel consumption.

For engine-related issues, see our diesel engine services.

Hot Water/Heating Systems

For cold weather work or frozen ground:

Inline heaters: Warm water (100-140°F), simpler, lower cost, adequate for moderate cold.

Boiler systems: Hot water (180°F+), handles frozen ground, more complex, higher fuel use.

If you work in cold climates, don't skimp on the heating system. Frozen water systems and inability to work frozen ground will cost you more than the upgrade.

See our winter preparation guide for cold weather operations.

Sizing by Application

Let me give you some real-world recommendations:

Utility Potholing (Your Primary Work)

Job profile: Multiple small excavations per day, urban/suburban locations, utility verification.

Recommended specs:

• Debris tank: 8-10 cubic yards
• CFM: 4,000-4,500
• Water: 800-1,000 gallons
• Boom: 18-20 feet

Why: Moderate tank handles 10-20 potholes. Enough CFM for reasonable speed. Water tank supports a full day with occasional hydrant fills. Standard boom reaches most situations.

General Contractor (Mixed Work)

Job profile: Various jobs — some potholing, some trenching, occasional larger excavations.

Recommended specs:

• Debris tank: 10-12 cubic yards
• CFM: 4,500-5,500
• Water: 1,000-1,200 gallons
• Boom: 20-22 feet

Why: Larger tank handles diverse work without constant dumping. Higher CFM handles heavier soil. Good water capacity for longer jobs.

Production Excavation (High Volume)

Job profile: Full-time excavation, multiple trucks, maximum productivity matters.

Recommended specs:

• Debris tank: 12-15 cubic yards
• CFM: 5,500-6,000+
• Water: 1,200-1,500 gallons
• Boom: 22-25 feet

Why: Maximum capacity and power for production work. Dump trips and water refills cost time — minimize them.

Tight Access/Urban Work

Job profile: City streets, tight spaces, weight-restricted roads, residential areas.

Recommended specs:

• Debris tank: 6-8 cubic yards
• CFM: 3,000-4,000
• Water: 500-700 gallons
• Compact chassis

Why: Smaller footprint gets into tight spaces. Lower GVW avoids weight restrictions. Nearby disposal and water access offset smaller capacities.

Remote/Rural Work

Job profile: Long travel to job sites, limited disposal and water access.

Recommended specs:

• Debris tank: 12-15 cubic yards
• CFM: 5,000-5,500
• Water: 1,400-1,500 gallons

Why: Maximize on-site capacity. Every trip to disposal or water costs significant time on remote jobs.

Cold Weather/Frozen Ground Specialist

Job profile: Year-round work in northern climates, frozen ground excavation.

Recommended specs:

• Full boiler system (not just inline heater)
• Insulated tanks (water and debris)
• Cold weather chassis package
• Standard or larger capacity

Why: Cold weather equipment is non-negotiable. Can't cut frozen ground without hot water. Frozen systems shut you down.

Consider Kaiser or Tornado for cold weather specialization.

Common Sizing Mistakes

Mistake 1: Buying Too Big

The thinking: "Bigger is better — I'll never outgrow it."

The reality:

• Higher purchase price
• Higher operating costs (fuel, maintenance)
• Higher insurance
• Weight limit problems
• Can't fit on tight sites
• Overkill for most jobs

Better approach: Size for your typical work, not your biggest possible job. Rent for the occasional large project.

Mistake 2: Buying Too Small

The thinking: "I'll save money and upgrade later."

The reality:

• Constant dump trips kill productivity
• Running out of water stops work
• Underpowered vacuum frustrates operators
• Can't take larger jobs
• Resale value suffers when you upgrade

Better approach: Size for your realistic workload, not your minimum. A slightly larger truck is a better long-term investment. See our costs guide for how sizing affects total cost of ownership.

Mistake 3: Mismatched Components

Examples:

• Big tank with small blower (slow to fill)
• Small water tank with big debris tank (constant refilling)
• High-output equipment on underpowered chassis (engine struggles)

Better approach: Buy balanced configurations. Manufacturers spec standard combinations for good reasons.

Mistake 4: Ignoring Operating Environment

Examples:

• Big truck for urban work with tight access
• Cold weather work without proper heating
• Remote work without adequate capacity

Better approach: Match the truck to where you actually work, not theoretical ideal conditions.

New vs. Used Sizing Considerations

Buying New

You can spec exactly what you need. Take time to get it right — you'll live with this truck for years.

Tip: Talk to your dealer about your actual applications. Good dealers help you spec appropriately rather than overselling.

Buying Used

You get what's available. Flexibility matters more than finding the "perfect" size.

Acceptable trade-offs:

• Slightly larger than ideal (higher costs, but works)
• Different brand than preferred (if specs are right)
• Older model with good specs (if maintained well)

Unacceptable trade-offs:

• Significantly undersized (kills productivity forever)
• Missing critical features for your work (cold weather, etc.)
• Poor maintenance history (problems regardless of size)

For used truck evaluation, see our costs guide.

Quick Reference: Sizing Summary

The Bottom Line

There's no universal "right size" for a hydrovac. The right size is the one that:

1. Handles your typical job efficiently
2. Fits where you need to work
3. Meets weight restrictions on your routes
4. Stays within your budget
5. Matches available operator skills

When in doubt, size for versatility. A well-matched 10-12 yard truck handles 80% of work without being overkill or underpowered.

And whatever size you buy, maintain it properly. A well-maintained 8-yard truck outperforms a neglected 15-yard truck every time. See our maintenance guide for keeping your equipment in top shape.

Questions About Sizing or Specs?

If you're evaluating a purchase and want a mechanic's perspective on what specs actually matter, I'm happy to help.

For service, maintenance, or repairs on any size hydrovac, I cover Pennsylvania, New Jersey, New York, and the DC/Maryland area.

Call me at 272-296-9637 or request service here.