Average score
Product 1: Ecovacs N30 PRO OMNI Robot...
4.2
Product 2: Ecovacs Deebot X9 Pro Omni...
4.3
Accessories and Tools
Product 1: Ecovacs N30 PRO OMNI Robot...
3.2

The reviews mention an optional cleaner stick and note Ecovacs removed the hidden cleaning tool from older docks, so accessory support is useful but less complete than some prior models.

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.

Aesthetic design and finish
Product 1: Ecovacs N30 PRO OMNI Robot...
4.3

Multiple reviewers call the robot and dock stylish, with black and white color options and a station design that looks more refined than older boxy Ecovacs docks.

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: Ecovacs N30 PRO OMNI Robot...
4.3

The app offers room control, suction and mop tuning, obstacle sensitivity, mapping edits and automation options, though base-station physical controls were reduced versus older models.

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: Ecovacs N30 PRO OMNI Robot...
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: Ecovacs N30 PRO OMNI Robot...
4.5

Mop lifting lets the N30 transition across carpets and rugs without soaking them, making mixed-floor cleaning more practical.

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: Ecovacs N30 PRO OMNI Robot...
4.8

Setup is consistently described as easy, with quick base assembly, straightforward app pairing and fast initial mapping.

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: Ecovacs N30 PRO OMNI Robot...
2.8

Battery life is adequate but not a strength; one reviewer saw steep drain at max power, while dock-based charging keeps autonomous operation convenient.

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: Ecovacs N30 PRO OMNI Robot...
3.6

The onboard bin and dust bag are accessible and functional, but the 2.6 L dock bag is smaller than some rivals and may need more frequent changes in busy homes.

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.

Build quality and durability
Product 1: Ecovacs N30 PRO OMNI Robot...
4.2

The design is described as robust and well-finished, with no reviewer raising major build-quality concerns.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Carpet — Medium-Pile Pickup
Product 1: Ecovacs N30 PRO OMNI Robot...
No score yet
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: Ecovacs N30 PRO OMNI Robot...
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: Ecovacs N30 PRO OMNI Robot...
4.6

Reviewers place it above many similarly priced rivals for cleaning tech and value, though navigation trails the best Roborock and Dreame competition.

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: Ecovacs N30 PRO OMNI Robot...
3.6

The app is clear and flexible, but some users may miss more convenient top-mounted dock controls and fully button-based operation.

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: Ecovacs N30 PRO OMNI Robot...
4.9

The extendable mop arm noticeably improves corner reach and solves a common weak spot of robot mops.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Dirty water sensor
Product 1: Ecovacs N30 PRO OMNI Robot...
No score yet
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: Ecovacs N30 PRO OMNI Robot...
4.5

The robot reliably returns to the dock for emptying, mop washing and drying, adding the hands-off experience buyers expect from an Omni dock.

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.

Dried-On Stain Removal
Product 1: Ecovacs N30 PRO OMNI Robot...
4.3

It handles light dried stains well and can clear tougher dried messes like ketchup with extra passes.

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: Ecovacs N30 PRO OMNI Robot...
4.4

Day-to-day use is simple once mapped, though cable clutter, tight spaces and the need for app familiarity keep it from being fully effortless.

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: Ecovacs N30 PRO OMNI Robot...
4.9

Edge cleaning is a standout strength thanks to the extending mop that reaches along walls and baseboards more thoroughly than many rivals.

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.

Edge‑Following Accuracy (Robot)
Product 1: Ecovacs N30 PRO OMNI Robot...
4.8

The robot generally tracks edges effectively when extending the mop, though room-layout complexity can still slow it down.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Emptying and Mess Control
Product 1: Ecovacs N30 PRO OMNI Robot...
4.5

Auto-emptying and dock maintenance reduce manual mess handling, though bag size limits how long some heavy-use households can go between changes.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Filtration / Dust Containment
Product 1: Ecovacs N30 PRO OMNI Robot...
4.2

A sealed bagged dock and washable filter support decent dust containment and air cleanliness for a mainstream robot vacuum.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Floor Drying Time
Product 1: Ecovacs N30 PRO OMNI Robot...
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.

Floorhead design
Product 1: Ecovacs N30 PRO OMNI Robot...
4.6

The cleaning head setup combines a main brush, side brush and dual rotating mop pads, with newer anti-tangle shaping that improves overall floor-contact behavior.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Floor shine after cleaning
Product 1: Ecovacs N30 PRO OMNI Robot...
4.5

Reviewers say floors look noticeably cleaner and even sparkling after mopping, especially on everyday dirt and light dried residue.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Fresh Liquid Pickup Speed
Product 1: Ecovacs N30 PRO OMNI Robot...
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-removal channel issues
Product 1: Ecovacs N30 PRO OMNI Robot...
4.8

The brush path does a good job funneling hair inward, so reviewers reported very few hair-channel cleanup annoyances.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Hair Pickup — Carpets
Product 1: Ecovacs N30 PRO OMNI Robot...
No score yet
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: Ecovacs N30 PRO OMNI Robot...
4.6

Dog hair and general fur pickup are consistently strong on everyday floors, especially with the anti-tangle brush system.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Hair‑Wrap / Tangle Resistance
Product 1: Ecovacs N30 PRO OMNI Robot...
4.9

The anti-tangle brush design is one of the product’s clearest wins, with reviewers specifically praising its resistance to wrapped hair.

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: Ecovacs N30 PRO OMNI Robot...
4.3

Fine dust pickup on hard floors is strong, with reviewers repeatedly describing solid single-pass dirt removal.

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: Ecovacs N30 PRO OMNI Robot...
4.6

It performs well on larger debris like crumbs and rice, usually clearing them in one or two passes.

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: Ecovacs N30 PRO OMNI Robot...
4.4

The dock uses hot water mop washing and warm-air drying, which improves post-clean maintenance and pad readiness.

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: Ecovacs N30 PRO OMNI Robot...
4.9

The extending mop arm and upgraded anti-tangle system are viewed as meaningful innovations rather than marketing fluff.

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.

Large debris handling
Product 1: Ecovacs N30 PRO OMNI Robot...
4.5

Everyday debris such as crumbs, rice and pet messes are handled confidently for a robot in this price tier.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Low-profile design
Product 1: Ecovacs N30 PRO OMNI Robot...
4.0

At around 10.4 cm tall, the robot is reasonably slim and can reach under some furniture, though it is not ultra-low-profile.

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: Ecovacs N30 PRO OMNI Robot...
4.5

The dock automation keeps upkeep low overall, but owners still need to replace bags, manage water tanks and occasionally clear problem areas.

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.

Maneuverability and Handling
Product 1: Ecovacs N30 PRO OMNI Robot...
3.7

It moves well in open areas, but tight corners and chair- or cable-heavy spots can slow it down or cause trouble.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Map and Path Efficiency (Robot Vacuums)
Product 1: Ecovacs N30 PRO OMNI Robot...
3.4

Mapping is fast and editable, but pathing and room segmentation are not always optimal compared with class leaders.

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: Ecovacs N30 PRO OMNI Robot...
4.7

The mop lift works as intended, allowing safer carpet transitions during mixed cleaning runs.

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: Ecovacs N30 PRO OMNI Robot...
4.7

Mopping is one of the N30 Pro Omni’s biggest strengths, with very good everyday scrubbing and edge reach.

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: Ecovacs N30 PRO OMNI Robot...
2.8

Standard modes are reasonably quiet, but max suction is clearly loud and one of the main tradeoffs.

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: Ecovacs N30 PRO OMNI Robot...
3.2

Obstacle handling is serviceable rather than best-in-class; it avoids major collisions but still struggles with cables and cramped layouts.

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: Ecovacs N30 PRO OMNI Robot...
4.5

Heated mop drying helps prevent damp-pad smells, a useful long-term hygiene benefit.

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.

Onboard tool storage
Product 1: Ecovacs N30 PRO OMNI Robot...
2.5

One reviewer specifically missed the hidden cleaning tools found on an older Ecovacs dock, so onboard storage is a step back here.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Ongoing ownership costs (bags, filters, batteries)
Product 1: Ecovacs N30 PRO OMNI Robot...
4.0

Running costs look moderate rather than minimal because the dock uses consumables and an optional cleaner stick is sold separately.

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 cleaning convenience
Product 1: Ecovacs N30 PRO OMNI Robot...
4.3

Vacuuming, mopping, auto-emptying and pad washing make this a highly convenient cleaner for everyday upkeep.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Overall opinion
Product 1: Ecovacs N30 PRO OMNI Robot...
4.7

The overall tone is strongly positive: reviewers see it as an easy recommendation with a few navigation and noise caveats.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Pet-Ready Features
Product 1: Ecovacs N30 PRO OMNI Robot...
4.9

Pet households are a strong fit thanks to hair pickup, anti-tangle behavior and solid day-to-day floor maintenance.

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: Ecovacs N30 PRO OMNI Robot...
4.7

Reviewers repeatedly frame it as high-end functionality at a more approachable price than flagship competitors.

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.

Self-cleaning cycle
Product 1: Ecovacs N30 PRO OMNI Robot...
4.7

The dock’s wash, dry and auto-empty cycle meaningfully reduces manual maintenance and keeps the robot ready for the next run.

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: Ecovacs N30 PRO OMNI Robot...
4.1

The dock supports standard water-based mopping and can use an optional cleaner stick that mixes solution into fresh water.

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.

Storage footprint and upright-stand stability
Product 1: Ecovacs N30 PRO OMNI Robot...
3.5

The dock is more compact than some full-service stations, but it is still a sizable appliance that may feel bulky in smaller homes.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Streaking / Residue
Product 1: Ecovacs N30 PRO OMNI Robot...
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: Ecovacs N30 PRO OMNI Robot...
2.8

It is fine in open rooms but can get hung up on tight corners, chair bases and loose cables.

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: Ecovacs N30 PRO OMNI Robot...
4.8

Suction is a clear strength, with 10,000 Pa class power translating to very strong everyday pickup.

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.

Suitability for small spaces
Product 1: Ecovacs N30 PRO OMNI Robot...
3.0

The robot can work in smaller homes, but tight layouts and the station’s footprint make it a better fit for moderately open floorplans.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Support and Reliability
Product 1: Ecovacs N30 PRO OMNI Robot...
4.1

Review sentiment suggests reliable everyday cleaning, but no review gives notable evidence of standout customer support.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Surface safety with attachments
Product 1: Ecovacs N30 PRO OMNI Robot...
4.5

Mop lifting helps it avoid wetting carpets and rugs during mixed runs, improving surface safety.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Under-Furniture Pickup
Product 1: Ecovacs N30 PRO OMNI Robot...
4.4

Its compact body and reach around chair legs help it clean some under-furniture areas better than bulkier robots.

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.

Value-for-money
Product 1: Ecovacs N30 PRO OMNI Robot...
4.6

For the feature set, reviewers generally see the N30 Pro Omni as delivering better value than many pricier alternatives.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Versatility
Product 1: Ecovacs N30 PRO OMNI Robot...
4.6

Multiple cleaning modes, mixed vacuum and mop runs and app-based room targeting make it versatile across different households and surfaces.

Product 2: Ecovacs Deebot X9 Pro Omni...
No score yet
Water tank
Product 1: Ecovacs N30 PRO OMNI Robot...
4.3

The dock’s 3.5 L clean-water and 3 L dirty-water tanks are practical for routine mopping and help limit refill frequency.

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.