Average score
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.2
P2
Product 2: Ecovacs Deebot X9 Pro Omni...
4.3
Accessories and Tools
P1Product 1: Dreametech D10 plus Robot Vacuum...
No score yet
P2
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
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.4
The white, minimal design is generally seen as sleek and less visually intrusive than darker robots, though the large dock is still prominent.
P2
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
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.4
The Mi Home or Dreame app suite provides robust mapping edits, no-go and no-mop zones, schedules, and per-room power and water settings. Usability is generally strong, but some reviewers note menus can feel busy and Wi‑Fi is 2.4GHz only.
P2
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
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.8
In at least one particulate test during auto-emptying, the system did not noticeably increase airborne dust, suggesting good sealing and containment.
P2
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
P1Product 1: Dreametech D10 plus Robot Vacuum...
No score yet
P2
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
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.2
Physical setup is quick (attach side brush, insert bag, charge), but optimal placement of the dock and app pairing take more attention, especially for mapping multiple floors.
P2
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
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.5
Battery life is frequently praised, with quoted runtimes around 150 to 180 minutes on lower power and the ability to recharge and resume. Recharging can take roughly 4.5 to 6 hours, and max power drains the battery much faster.
P2
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
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.4
The onboard bin is small (around 400mL in several specs) but the dock’s sealed bag (commonly 2.5L; one D10s Plus review cites 4L) enables weeks of hands-off emptying. A few notes mention debris can spill if the robot is carried between rooms.
P2
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 — High-Pile Pickup
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.9
High-pile performance can be very strong in controlled tests, including pet-hair pickup, but real-world clutter and fine dust can still require higher suction and occasional manual help.
P2Product 2: Ecovacs Deebot X9 Pro Omni...
No score yetCarpet — Low-Pile Pickup
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.3
Low-pile carpet results are generally good, with most debris removed in tests; occasional misses on fine dust or sugary or kitty-litter style particles were noted.
P2Product 2: Ecovacs Deebot X9 Pro Omni...
No score yetCarpet — Medium-Pile Pickup
P1
Product 1: Dreametech D10 plus Robot Vacuum...
3.6
Carpet performance is solid for maintenance cleaning but can struggle with fine flour-like dust without higher suction. One comparative test placed it near the top for budget robots, though it is not a deep-clean replacement for an upright.
P2
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.
Child lock
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.5
Child lock and do-not-disturb style settings are available via the app to prevent accidental starts and noisy auto-emptying at night.
P2Product 2: Ecovacs Deebot X9 Pro Omni...
No score yetClogging and debris prevention
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.6
Auto-emptying was generally effective at clearing dense debris, and one review credits a DualBoost-style airflow design with reducing clogs during emptying.
P2
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
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.3
In a multi-robot budget comparison, it scored near the top for cleaning while delivering the best value per dollar, though a Roborock competitor led overall.
P2
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
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.4
Physical buttons are simple for start, home, and spot cleaning, backed by app controls. Several reviewers mention helpful (if sometimes unnecessary) voice prompts.
P2
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.
Cord management
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.4
The dock’s cable routing and coil holder help tidy excess cord slack behind the base, improving placement neatness.
P2Product 2: Ecovacs Deebot X9 Pro Omni...
No score yetDirty water sensor
P1Product 1: Dreametech D10 plus Robot Vacuum...
No score yet
P2
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)
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.4
When the robot successfully returns home, emptying is highly reliable and clears even dense debris; however, in cluttered environments some reviewers saw missed docks or mid-run stranding that prevents auto-emptying until rescued.
P2
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
P1
Product 1: Dreametech D10 plus Robot Vacuum...
3.4
Auto-emptying is loud but brief (a few seconds), commonly reported around the low 60 dB range and often compared to a quick jet-like burst.
P2Product 2: Ecovacs Deebot X9 Pro Omni...
No score yetDried-On Stain Removal
P1Product 1: Dreametech D10 plus Robot Vacuum...
No score yet
P2
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
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.5
With schedules, room targeting, and auto-emptying, day-to-day use can be largely hands-off, but it works best when floors are prepped and mopping is treated as a light maintenance feature.
P2
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)
P1Product 1: Dreametech D10 plus Robot Vacuum...
No score yet
P2
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
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.8
Auto-emptying generally leaves the onboard bin nearly clean and reduces mess versus manual dumping, though moving the robot can let some debris fall from internal cavities.
P2Product 2: Ecovacs Deebot X9 Pro Omni...
No score yetFilter-change indicator
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.3
The app can track accessory life, including filter and brush runtime, helping prompt cleaning or replacement.
P2Product 2: Ecovacs Deebot X9 Pro Omni...
No score yetFiltration / Dust Containment
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.5
Bagged self-emptying and filters help keep dust contained; one review notes an E12 HEPA filter and another highlights cleaner, more sanitary emptying versus manual dumping.
P2Product 2: Ecovacs Deebot X9 Pro Omni...
No score yetFloor Drying Time
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.2
Moderate water flow dries quickly for maintenance cleaning, while the highest water setting takes longer to dry.
P2
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
P1Product 1: Dreametech D10 plus Robot Vacuum...
No score yet
P2
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
P1
Product 1: Dreametech D10 plus Robot Vacuum...
5.0
Hair pickup is excellent, with multiple tests reporting near-total removal on carpet when suction is appropriately set.
P2
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‑Wrap / Tangle Resistance
P1
Product 1: Dreametech D10 plus Robot Vacuum...
2.9
The stock brush can wrap long hair, requiring periodic clearing with the included cutter tool. Some reviewers note optional brush upgrades can greatly reduce tangling.
P2
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
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.5
Hard-floor pickup is consistently excellent, often near complete removal in lab tests. Very low suction modes may leave some fine dust, but Standard or Turbo typically finishes the job.
P2
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
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.5
Large debris pickup on hard floors is strong overall, though a single side brush can occasionally flick particles and may benefit from a second pass or higher power for complete cleanup.
P2
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
P1Product 1: Dreametech D10 plus Robot Vacuum...
No score yet
P2
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
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.5
For its price tier, reviewers highlight a rare combination of LiDAR mapping, auto-emptying, and granular app control; the main missing innovation versus flagships is consistent AI object recognition (except in the D10s Plus variant review).
P2
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
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.2
At roughly 3.8 inches tall, it fits under many sofas and cabinets, improving under-furniture reach for routine cleaning.
P2
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
P1
Product 1: Dreametech D10 plus Robot Vacuum...
3.5
Routine upkeep includes swapping dock bags every few weeks, cleaning filters and sensors periodically, clearing hair from brushes, and rinsing or air-drying the mop pad after use.
P2
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)
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.3
LiDAR mapping is fast and accurate, enabling tidy, efficient cleaning paths and strong room segmentation. Multi-map and changing door or dock positions can occasionally disrupt schedules or docking.
P2
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
P1Product 1: Dreametech D10 plus Robot Vacuum...
No score yet
P2
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
P1
Product 1: Dreametech D10 plus Robot Vacuum...
3.5
Mopping is a basic cloth pad wipe: helpful for light maintenance and freshening hard floors, but not effective on dried-on grime or deep stains, and it requires manual pad care.
P2
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
P1
Product 1: Dreametech D10 plus Robot Vacuum...
3.9
On lower modes it is generally quiet and unobtrusive, while Turbo is noticeably louder. Several tests put cleaning around the high 40s to mid 60s dB depending on mode.
P2
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)
P1
Product 1: Dreametech D10 plus Robot Vacuum...
3.3
Most D10 Plus reviews describe basic bumper-based avoidance that can hit cords and small objects, so no-go zones and tidier floors help. A separate D10s Plus review highlights AI camera avoidance that performs much better with clutter.
P2
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
P1Product 1: Dreametech D10 plus Robot Vacuum...
No score yet
P2
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)
P1
Product 1: Dreametech D10 plus Robot Vacuum...
3.5
Expect recurring costs for dock bags plus periodic filter and mop-pad replacements, though one reviewer estimates bag costs can be relatively low annually depending on use.
P2
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
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.5
Overall sentiment is strongly positive, emphasizing reliability, mapping, and self-empty convenience, with most reservations centered on basic mopping and clutter handling.
P2Product 2: Ecovacs Deebot X9 Pro Omni...
No score yetPet-Ready Features
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.6
Reviews consistently report strong pet-hair pickup and the convenience of self-emptying for fur, though keeping cords and clutter off the floor helps prevent interruptions.
P2
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
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.6
Repeatedly framed as a standout value under about $400, with some reviewers calling its feature set and performance closer to pricier models.
P2
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
P1
Product 1: Dreametech D10 plus Robot Vacuum...
3.1
Control typically runs through the Mi Home or Dreame app, and one reviewer notes account and profile creation can feel intrusive. A related D10s Plus review describes an onboard camera for remote monitoring, which may raise additional privacy considerations.
P2Product 2: Ecovacs Deebot X9 Pro Omni...
No score yetSelf-cleaning cycle
P1Product 1: Dreametech D10 plus Robot Vacuum...
No score yet
P2
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
P1Product 1: Dreametech D10 plus Robot Vacuum...
No score yet
P2
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.
Stair Cleaning
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.7
Cliff and anti-drop sensors worked reliably in testing, with reviewers comfortable letting it clean near stair edges.
P2Product 2: Ecovacs Deebot X9 Pro Omni...
No score yetStorage footprint and upright-stand stability
P1
Product 1: Dreametech D10 plus Robot Vacuum...
2.8
The self-empty base is sizeable and needs generous clearance for consistent docking, making placement harder in small homes or tight corners.
P2Product 2: Ecovacs Deebot X9 Pro Omni...
No score yetStreaking / Residue
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.5
On sealed hard floors, mopping is reported to leave minimal streaks or water marks at moderate water settings; heavier wet settings can leave faint marks similar to a normal mop.
P2
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
P1
Product 1: Dreametech D10 plus Robot Vacuum...
3.5
Experiences vary: some testers saw frequent snags on cords or tight spots, while others reported only occasional hang-ups. Threshold and transition handling is decent but not unlimited.
P2
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
P1
Product 1: Dreametech D10 plus Robot Vacuum...
4.4
Most testers describe suction as strong for the price (often cited at 4,000Pa, with one related D10s Plus review noting 5,000Pa). Standard mode handles everyday debris well; fine dust in carpet can require Turbo.
P2
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.
Surface safety with attachments
P1
Product 1: Dreametech D10 plus Robot Vacuum...
3.4
Because mopping is a wet-pad drag system, reviewers recommend using no-mop zones and removing the module for carpets; one cautions porous flooring near the dock if the wet pad is left attached.
P2Product 2: Ecovacs Deebot X9 Pro Omni...
No score yetUnder-Furniture Pickup
P1Product 1: Dreametech D10 plus Robot Vacuum...
No score yet
P2
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
P1
Product 1: Dreametech D10 plus Robot Vacuum...
3.6
The water tank is small (often 145mL; one related model cites a larger tank), with adjustable water flow. Large hard-floor areas may require refills.
P2
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.