Compare Roborock Qrevo Curv Vacuum and Mop vs Ecovacs Deebot X9 Pro Omni Robot Vacuum and Mop

P1 Roborock Qrevo Curv Vacuum and Mop
P2 Ecovacs Deebot X9 Pro Omni Robot Vacuum and Mop

Comparison Takeaways

Roborock Qrevo Curv Vacuum and Mop

Where It Has the Edge

  • Area Rug Handling is 4.5 vs 3.4. For mixed flooring, mop lifting and carpet detection are praised for keeping rugs dry while maintaining cleaning coverage;...
  • Bin and Bag is 4.6 vs 3.7. Reviews commonly mention a disposable dust bag in the dock plus an onboard bin; overall feedback is that...
  • Battery and Charging is 4.7 vs 3.9. Battery life and efficiency are rated highly (including strong coverage per charge), making it a good fit for...
  • Docking and Auto-Empty Reliability (Robot) is 4.7 vs 3.9. Docking and auto-empty reliability are repeatedly praised: the robot returns consistently, empties well, and handles mop washing/drying and...

Ecovacs Deebot X9 Pro Omni Robot Vacuum and Mop

Where It Has the Edge

  • Dried-On Stain Removal is 4.9 vs 3.8. Reviewers cite exceptional performance on dried-on messes, including lab-style scoring that places it near the top of recorded...
  • Solution / Liquid system is 4.4 vs 3.6. A detergent reservoir/auto-dispensing system and adjustable water output are noted across several reviews, enabling hands-off mopping. A few...
  • Odor control is rated 4.8 while the other product has no score yet. Hot-air drying and regular mop washing are repeatedly credited with preventing the damp, mildew-like smell that some robot...
  • Innovation compared to competitors is rated 4.7 while the other product has no score yet. Reviewers frequently call out the roller self-washing concept and BLAST airflow path as meaningful advances over older hybrids....
Average score
Product 1: Roborock Qrevo Curv Vacuum and...
4.5
Product 2: Ecovacs Deebot X9 Pro Omni...
4.3
Accessories and Tools
Product 1: Roborock Qrevo Curv Vacuum and...
No score yet
Product 2: Ecovacs Deebot X9 Pro Omni...
4.0

Unboxings typically include the robot, dock, ramp, cord, and manuals, with a dust bag preinstalled. Multiple reviewers note that extra consumables (spare bags or detergent) may not be included.

Adaptive chassis lift
Product 1: Roborock Qrevo Curv Vacuum and...
4.6

The adaptive chassis lift/threshold capability is a standout differentiator, helping it clear taller transitions than many robots. A few reviewers suggest real-world limits can be below marketing claims, but it’s still viewed as meaningfully better than average.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Aesthetic design and finish
Product 1: Roborock Qrevo Curv Vacuum and...
4.6

Its curved, modern dock and polished styling are frequently described as more living-room-friendly than boxier competitors. Overall sentiment on design is strongly positive.

Product 2: Ecovacs Deebot X9 Pro Omni...
4.6

Design and finish are consistently praised, with multiple reviewers calling the robot and dock premium-looking (brushed/metal-like textures and a sleeker base). Even reviewers with performance complaints tend to like the aesthetics.

AI, Smart, App and Automation
Product 1: Roborock Qrevo Curv Vacuum and...
4.5

The app is consistently described as feature-rich, with strong automation options (room-by-room settings, scheduling, empty frequency, remop triggers, etc.). Overall sentiment is that the software is powerful without being overly hard to use.

Product 2: Ecovacs Deebot X9 Pro Omni...
4.5

The Ecovacs app is widely praised for organization and depth (routines, maps, barriers, dock controls), and multiple sources mention Matter and voice features (including Yiko). A few note that some settings are buried or that the robot can be overly chatty.

Airflow blowback
Product 1: Roborock Qrevo Curv Vacuum and...
No score yet
Product 2: Ecovacs Deebot X9 Pro Omni...
4.3

Multiple reviewers note reduced debris scattering compared with earlier models, sometimes crediting a slowed or redesigned side brush. Conversely, some negative experiences describe debris drops around thresholds or during return-to-dock events.

Area Rug Handling
Product 1: Roborock Qrevo Curv Vacuum and...
4.5

For mixed flooring, mop lifting and carpet detection are praised for keeping rugs dry while maintaining cleaning coverage; reviewers generally see it as well-suited to homes with area rugs.

Product 2: Ecovacs Deebot X9 Pro Omni...
3.4

Carpet detection is described as competent, but thick rugs and thresholds are recurring pain points in negative reviews. The robot is also described as limited to standard threshold heights rather than newer advanced climbing systems.

Assembly and Setup
Product 1: Roborock Qrevo Curv Vacuum and...
4.7

Setup is described as straightforward: the dock is largely ready out of the box, pairing/mapping is quick, and most complexity comes from exploring app settings rather than assembly.

Product 2: Ecovacs Deebot X9 Pro Omni...
4.0

Setup is often described as straightforward, but several reviews mention initial firmware updates, mapping hiccups, or time spent editing room divisions. Planning a little extra time for first-run mapping improves the experience.

Battery and Charging
Product 1: Roborock Qrevo Curv Vacuum and...
4.7

Battery life and efficiency are rated highly (including strong coverage per charge), making it a good fit for larger homes or multi-room schedules.

Product 2: Ecovacs Deebot X9 Pro Omni...
3.9

Battery impressions are mixed: official low-power runtimes are strong, but measured testing and higher-power settings can look below average for efficiency and coverage per charge. Recharge-and-resume helps, and some reviewers still find it sufficient for typical homes.

Bin and Bag
Product 1: Roborock Qrevo Curv Vacuum and...
4.6

Reviews commonly mention a disposable dust bag in the dock plus an onboard bin; overall feedback is that it reduces dust mess and feels appropriately sized for typical households.

Product 2: Ecovacs Deebot X9 Pro Omni...
3.7

Several reviews note the robot’s internal bin is small for a flagship, increasing dependence on the dock. The dock’s disposable bag is described as large-capacity, but spare bags aren’t always included.

Carpet — Medium-Pile Pickup
Product 1: Roborock Qrevo Curv Vacuum and...
4.6

Carpet deep-clean performance is rated very strong in testing, placing it near the top tier among vacuum+mop hybrids.

Product 2: Ecovacs Deebot X9 Pro Omni...
4.7

Carpet performance is frequently rated near the top, with strong deep-clean results and above-average pickup on rugs. Some comparisons still argue the X8 is close enough on most tests that the X9’s premium is hard to justify.

Clogging and debris prevention
Product 1: Roborock Qrevo Curv Vacuum and...
No score yet
Product 2: Ecovacs Deebot X9 Pro Omni...
3.2

This is a key split point: multiple reviews report clogs with medium/large debris, pet hair, or messy mixtures, sometimes without timely alerts. Others report strong day-to-day debris handling with reduced scattering, suggesting performance depends on debris type and home layout.

Comparative performance
Product 1: Roborock Qrevo Curv Vacuum and...
No score yet
Product 2: Ecovacs Deebot X9 Pro Omni...
4.6

In roundup-style coverage it’s presented as a top performer and award winner, but some side-by-side comparisons conclude the less expensive X8 (or other flagships) can be a better overall buy. The X9’s strengths are usually framed as best-in-class mopping and very strong all-around cleaning.

Controls and UI
Product 1: Roborock Qrevo Curv Vacuum and...
4.5

Controls are generally praised: reviewers cite an intuitive app, useful remote-control features (e.g., pin-and-go), and broad customization. Some note competitor apps can feel more confusing, making Roborock’s UI a relative bright spot.

Product 2: Ecovacs Deebot X9 Pro Omni...
4.0

App controls are generally seen as excellent, but physical controls and map-editing workflows get criticism in some reviews (sluggish button response or tedious confirmation steps). After setup, day-to-day control is usually straightforward.

Corner Cleaning (Robot)
Product 1: Roborock Qrevo Curv Vacuum and...
4.6

Corner cleaning gets frequent praise thanks to an extending side brush, improving reach into tight corners. One stress test notes the side brush can scatter debris in extreme scenarios, but overall corner performance is viewed as above average.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Crevice / Groove Pickup (Hard Floors)
Product 1: Roborock Qrevo Curv Vacuum and...
3.5

Crevice/groove pickup is noted as a relative weak spot: one review calls it average compared to the robot’s otherwise high-performing hard-floor and carpet results.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Dirty water sensor
Product 1: Roborock Qrevo Curv Vacuum and...
4.5

A dirty-water / dirt-detection sensor is credited with enabling remop/extra wash behavior, helping prevent spreading grime and improving hands-off cleaning.

Product 2: Ecovacs Deebot X9 Pro Omni...
4.6

Some reviews call out a dirty-water sensing feature in the dock that can adjust washing based on how dirty the pads are. It’s consistently described as a higher-end automation feature rather than a must-have.

Docking and Auto-Empty Reliability (Robot)
Product 1: Roborock Qrevo Curv Vacuum and...
4.7

Docking and auto-empty reliability are repeatedly praised: the robot returns consistently, empties well, and handles mop washing/drying and refills with little fuss.

Product 2: Ecovacs Deebot X9 Pro Omni...
3.9

The OMNI dock is broadly viewed as full-featured and convenient, combining auto-empty, refill, and mop washing/drying. A minority of reports mention a one-off auto-empty clog/failure or debris dropping on the way back to the dock, so reliability is strong but not flawless.

Dock noise
Product 1: Roborock Qrevo Curv Vacuum and...
4.6

Dock emptying noise is described as relatively quiet for the category, including one report around ~67 dB.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Dried-On Stain Removal
Product 1: Roborock Qrevo Curv Vacuum and...
3.8

In at least one standardized test, dried-on stain performance is described as more mid-pack than class-leading—good, but not the standout reason to buy.

Product 2: Ecovacs Deebot X9 Pro Omni...
4.9

Reviewers cite exceptional performance on dried-on messes, including lab-style scoring that places it near the top of recorded results. Real-home testers also report it can scrub sticky spots that older robot mops often leave behind, though not always perfectly.

Ease of use
Product 1: Roborock Qrevo Curv Vacuum and...
4.5

Day-to-day ownership is described as low-effort because the dock automates most chores; typical hands-on tasks are water refills/empties and occasional cleaning of the dock tray/consumables.

Product 2: Ecovacs Deebot X9 Pro Omni...
4.0

When everything is dialed in, reviewers describe an almost set-and-forget experience with strong automation. Negative experiences typically stem from clogs, threshold issues, or mapping inaccuracies that demand more intervention.

Edge and Baseboard Cleaning (Hard Floors)
Product 1: Roborock Qrevo Curv Vacuum and...
4.6

Edge coverage is repeatedly highlighted: an extending mop pad and sweep arm help it clean closer to walls and baseboards than many rivals. Reviewers still wish for true baseboard scrubbing, but edge pickup is considered a strength.

Product 2: Ecovacs Deebot X9 Pro Omni...
4.4

Edge cleaning is typically a strength thanks to extending brush/mop behavior, with several reviewers noting good wall-hugging and baseboard coverage. A common caveat is that the roller shape may miss a strip near certain appliances or toe-kicks.

Emptying and Mess Control
Product 1: Roborock Qrevo Curv Vacuum and...
4.6

The bagged emptying system is viewed as clean and convenient, with quiet emptying noted in at least one review and helpful indicators when water tanks need attention.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Floor Drying Time
Product 1: Roborock Qrevo Curv Vacuum and...
No score yet
Product 2: Ecovacs Deebot X9 Pro Omni...
4.6

Lower water left behind and hot-air drying are commonly noted, which can help floors dry faster and reduce lingering dampness. Some owners still mention long deep-clean cycles that may include recharge breaks, but drying performance is generally praised.

Fresh Liquid Pickup Speed
Product 1: Roborock Qrevo Curv Vacuum and...
No score yet
Product 2: Ecovacs Deebot X9 Pro Omni...
4.6

Several sources emphasize that the roller design can handle small wet spills by separating dirty water rather than dragging a damp pad across the floor. Demo-style testing (e.g., spilled milk) suggests it can clean quickly with minimal smearing compared with traditional pad mops.

Hair Pickup — Carpets
Product 1: Roborock Qrevo Curv Vacuum and...
4.5

For carpet hair, reviews and pet-hair testing place it among the better performers, though some results suggest two passes may still be needed for the most thorough pickup.

Product 2: Ecovacs Deebot X9 Pro Omni...
4.7

Carpet hair pickup is widely reported as strong, including high pet-hair percentages in testing and positive real-home pet results. Performance can drop if debris clogs the airflow path or during tricky threshold transitions.

Hair Pickup — Hard Floors
Product 1: Roborock Qrevo Curv Vacuum and...
4.8

Hard-floor hair pickup is described as excellent in pet-focused testing, with near-perfect results reported.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Hair‑Wrap / Tangle Resistance
Product 1: Roborock Qrevo Curv Vacuum and...
4.6

Hair‑wrap resistance is a major highlight: the split/DuoDivide-style roller design earns perfect or near-perfect tangle-test results in multiple discussions. One reviewer still noted minor hair accumulation in certain joints, but overall sentiment remains very strong.

Product 2: Ecovacs Deebot X9 Pro Omni...
4.4

Many sources highlight anti-tangle brush features (ZeroTangle/active hair removal) with lab tests showing near-zero tangling. At least one reviewer still experienced significant hair wrapping during problem runs, so it’s excellent but not guaranteed.

Hard Floor — Fine Dust Pickup
Product 1: Roborock Qrevo Curv Vacuum and...
4.8

Testing-focused reviews describe excellent fine-dust pickup on hard floors, with strong results across small particulate debris.

Product 2: Ecovacs Deebot X9 Pro Omni...
4.7

Hard-floor dust pickup is consistently described as strong, with reviewers noting reliable capture of micro debris and fine dust. Some negative reviews still credit it for routine dust pickup even when larger-debris clogs occur.

Hard Floor — Large Debris Intake
Product 1: Roborock Qrevo Curv Vacuum and...
4.8

Large-debris intake is repeatedly described as excellent in testing, handling bigger particles without major issues.

Product 2: Ecovacs Deebot X9 Pro Omni...
4.7

Large-debris handling is generally good, but multiple reviews note edge cases where larger particles, thresholds, or entering/exiting the dock can lead to drops. Very large debris can also contribute to clogs on some floors.

Heating element
Product 1: Roborock Qrevo Curv Vacuum and...
4.6

Hot-water mop washing and heated/warm-air drying are consistently praised for hygiene and for keeping mop pads from staying damp between runs.

Product 2: Ecovacs Deebot X9 Pro Omni...
4.6

Heated mop washing and heated-air drying are frequently highlighted, with some reviews noting adjustable wash/dry behavior. This is repeatedly framed as a premium feature that improves hygiene and reduces damp odors.

Innovation compared to competitors
Product 1: Roborock Qrevo Curv Vacuum and...
No score yet
Product 2: Ecovacs Deebot X9 Pro Omni...
4.7

Reviewers frequently call out the roller self-washing concept and BLAST airflow path as meaningful advances over older hybrids. It’s still in a competitive field (other brands have strong threshold handling or alternative mop designs), but the X9’s implementation is often viewed as one of the more complete packages.

Low-profile design
Product 1: Roborock Qrevo Curv Vacuum and...
No score yet
Product 2: Ecovacs Deebot X9 Pro Omni...
3.9

Internal LiDAR is positioned as a design win for getting into tighter spaces compared with tower designs. Measured height is still around the high-3-inch range, so ultra-low furniture may remain out of reach.

Maintenance requirements
Product 1: Roborock Qrevo Curv Vacuum and...
4.4

Maintenance is often framed as low thanks to automation, but owners still need to refill clean water, empty dirty water, replace bags/consumables, and occasionally clean the dock tray and brushes.

Product 2: Ecovacs Deebot X9 Pro Omni...
4.2

Routine upkeep is generally reduced thanks to dock automation and app reminders, but several reviewers still recommend periodic tank cleaning and occasional brush/roller clearing. Sticky, paste-like messes can create a bigger cleanup burden.

Map and Path Efficiency (Robot Vacuums)
Product 1: Roborock Qrevo Curv Vacuum and...
4.7

Lidar mapping and route planning are described as fast and efficient, with organized straight-line coverage and solid room handling/multi-level mapping.

Product 2: Ecovacs Deebot X9 Pro Omni...
4.0

Some reviewers describe fast, efficient coverage and strong navigation once maps are set. Others report inaccurate initial mapping (especially in larger rooms) and more manual tweaking than expected for a flagship.

Mop lifting system
Product 1: Roborock Qrevo Curv Vacuum and...
4.6

Mop lifting is frequently cited as effective (often framed around a ~17mm lift), enabling it to vacuum carpets/rugs without soaking them.

Product 2: Ecovacs Deebot X9 Pro Omni...
4.6

Multiple reviews mention automatic lifting behavior to protect carpets (mop lift, and in some descriptions additional component lifting). This generally helps with mixed-floor homes, though the robot is still limited on very tall thresholds or very thick rugs.

Mopping performance
Product 1: Roborock Qrevo Curv Vacuum and...
4.5

Mopping is broadly praised—dual spinning pads with adjustable wetness tackle everyday grime and paw prints well, and the extending mop pad improves edge coverage. A few reviewers still give the edge to the best-in-class moppers for heavy stains, but Curv is considered an excellent all‑around performer.

Product 2: Ecovacs Deebot X9 Pro Omni...
4.6

The self-washing roller mop is repeatedly called the standout feature, delivering strong scrubbing and excellent day-to-day hard-floor cleaning. A few tests found minor limitations (toe-kicks/appliances it can’t slide under, or slight stickiness/residue on messy stress tests), but it still ranks among the best.

Noise level
Product 1: Roborock Qrevo Curv Vacuum and...
No score yet
Product 2: Ecovacs Deebot X9 Pro Omni...
4.4

Operational noise is generally described positively (quiet or unobtrusive), and some coverage suggests BLAST aims to improve performance without a big noise penalty. Few reviews provide direct measurements, so perceptions dominate.

Obstacle Avoidance (Robot)
Product 1: Roborock Qrevo Curv Vacuum and...
4.0

Obstacle avoidance is usually described as good for larger items and many everyday obstacles, but several reviewers call out missed small cables/cords. In cable-heavy rooms, it may snag or stop, so floor prep or no-go zones are recommended.

Product 2: Ecovacs Deebot X9 Pro Omni...
4.2

Obstacle avoidance is generally rated above average, with good performance around common household items. Still, multiple reviewers report occasional real-world snags (chair legs, protrusions, or clutter), so it’s not consistently flawless.

Odor control
Product 1: Roborock Qrevo Curv Vacuum and...
No score yet
Product 2: Ecovacs Deebot X9 Pro Omni...
4.8

Hot-air drying and regular mop washing are repeatedly credited with preventing the damp, mildew-like smell that some robot mops develop. A few owners still clean the dirty-water tank regularly to avoid odors.

Ongoing ownership costs (bags, filters, batteries)
Product 1: Roborock Qrevo Curv Vacuum and...
No score yet
Product 2: Ecovacs Deebot X9 Pro Omni...
3.2

Ongoing costs can include disposable dust bags and detergent, and some reviews cite specific replacement pricing. This contributes to the sense that the X9’s total cost of ownership is premium, especially versus the X8.

Overall opinion
Product 1: Roborock Qrevo Curv Vacuum and...
4.6

Across the reviews, Qrevo Curv lands as a top-tier vacuum+mop with strong cleaning results, a highly automated dock, and smart navigation. Praise centers on edge/corner reach and pet-hair handling, while the most common knocks are premium pricing and imperfect cable avoidance.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Pet-Ready Features
Product 1: Roborock Qrevo Curv Vacuum and...
4.6

Multiple reviews frame it as a great choice for pet owners thanks to strong hair pickup, anti-tangle brush design, and camera/app features (where enabled) for monitoring. Pet homes with lots of cords still need some floor prep.

Product 2: Ecovacs Deebot X9 Pro Omni...
4.7

Pet-focused commentary is largely positive: tests show strong pet-hair pickup and many highlight pet-oriented app features. The main pet-related downside raised is that heavy hair and larger debris can still contribute to clogs in certain homes.

Price and Value
Product 1: Roborock Qrevo Curv Vacuum and...
3.9

The price is repeatedly called premium (often framed around a ~$1,600 MSRP), and several reviewers recommend waiting for discounts. When on sale, value is described as far more compelling; a few reviewers question whether camera/chassis-lift extras are worth the upcharge versus cheaper variants or rivals.

Product 2: Ecovacs Deebot X9 Pro Omni...
3.5

Value is polarized: some reviewers say the performance and automation justify the splurge, while others recommend it only on sale or prefer the cheaper X8/competitors at full MSRP. The $200+ gap to close siblings is a recurring theme.

Privacy controls
Product 1: Roborock Qrevo Curv Vacuum and...
4.3

Camera-based features (obstacle recognition, remote viewing/voice) bring privacy considerations. Reviews note the camera can be disabled/off by default, and a camera-free variant exists for buyers who prioritize privacy.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Self-cleaning cycle
Product 1: Roborock Qrevo Curv Vacuum and...
4.5

The dock’s self-cleaning base/tray features reduce manual scrubbing, though reviewers still expect periodic cleaning to keep things fresh.

Product 2: Ecovacs Deebot X9 Pro Omni...
4.6

Both the robot and dock emphasize self-cleaning: the roller refreshes during runs, and the dock can wash and dry the mop and clean its basin. Reviewers still report occasional manual cleanup after unusually sticky or heavy messes.

Solution / Liquid system
Product 1: Roborock Qrevo Curv Vacuum and...
3.6

Most reviewers say detergent dosing is manual (add solution to the clean-water tank rather than a dedicated auto-dosing reservoir), while one review lists a detergent capacity/mixing capability. Net takeaway: plan for at least some manual solution handling.

Product 2: Ecovacs Deebot X9 Pro Omni...
4.4

A detergent reservoir/auto-dispensing system and adjustable water output are noted across several reviews, enabling hands-off mopping. A few sources mention proprietary-solution recommendations or smaller solution tanks, which can increase refills or cost.

Streaking / Residue
Product 1: Roborock Qrevo Curv Vacuum and...
No score yet
Product 2: Ecovacs Deebot X9 Pro Omni...
4.2

Many reviews report low water left behind and good streak control, and some highlight adjustable moisture settings. However, a few stress tests (jelly or flour-and-water paste) left mild residue or streaks, indicating outcomes depend on mess type and settings.

Stuck resistance
Product 1: Roborock Qrevo Curv Vacuum and...
3.6

Adaptive lift helps it clear thresholds and some obstacles, but cable snags and occasional attempts to 'climb' awkward objects can still interrupt runs in some homes.

Product 2: Ecovacs Deebot X9 Pro Omni...
3.6

Reports vary from near trouble-free operation to frequent help alerts depending on home layout. Thresholds and odd obstacles can cause wedging or debris drops in some tests, while careful mapping/no-go zones improves reliability for others.

Suction and Airflow
Product 1: Roborock Qrevo Curv Vacuum and...
4.5

Vacuuming performance is described as strong in real homes and on carpets, helped by high rated suction. One evaluation calls out only average airflow/bench suction and weaker performance in tight crevices compared with its overall cleaning results.

Product 2: Ecovacs Deebot X9 Pro Omni...
4.6

Most reviews describe very strong pickup driven by Ecovacs’ BLAST airflow approach, with top-tier results on both hard floors and carpet. A few reviewers say the real-world improvement over the X8 is modest and that large debris can still trigger drops or clogs.

Under-Furniture Pickup
Product 1: Roborock Qrevo Curv Vacuum and...
No score yet
Product 2: Ecovacs Deebot X9 Pro Omni...
3.7

The internal LiDAR approach avoids a tall turret and helps it reach under more furniture than tower-based bots. Still, reviewers note the roller mop can’t slide under some low-clearance areas the way flat pads can.

Water tank
Product 1: Roborock Qrevo Curv Vacuum and...
4.6

Reviews consistently mention separate clean/dirty water tanks plus onboard water handling that keeps pads wet. Tank refills/empties are a routine task, but capacity and adjustable water use are generally seen as practical for whole-home runs.

Product 2: Ecovacs Deebot X9 Pro Omni...
4.1

The clean/dirty tank setup is commonly described as easy to use, but there are tradeoffs: some miss transparent or externally visible tanks, some describe smaller/hidden tanks requiring more frequent refills, and dirty tanks can have corners that trap grime.