Robotic pool cleaner comparison

Dolphin M550 vs Dolphin T55i

A side-by-side comparison of pool fit, cleaning coverage, filtration, controls and the better Pool Express option.

By Brian Williamson, Pool Express product specialist
Updated November 9, 2026

Better alternative

A stronger Pool Express option

Dolphin M550 and Dolphin T55i are compared feature by feature below. For a stronger Pool Express option, consider Dolphin Quantum. Inground pools up to 50 ft that need floor, wall and waterline cleaning, with fine debris.

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M-Line

Dolphin M550

Inground pools up to 50 ft that need floor, wall and waterline cleaning with app control, Pick-Up and a caddy.

Listed price $1,999

View better alternatives

T-Line

Dolphin T55i

Inground pools up to 50 ft that need floor, wall and waterline cleaning, with fine debris.

Listed price $1,699

View better alternatives

A better alternative

What we recommend instead

Pool Express pick

Dolphin Quantum

Inground pools up to 50 ft that need floor, wall and waterline cleaning, with fine debris.

$1,649

Buy Dolphin Quantum

Buying guidance

Dolphin M550 or Dolphin T55i: our take

Dolphin M550 and Dolphin T55i are compared on pool fit, cleaning reach, debris handling, controls and ownership details. The recommendation is based on the job the robot must do—not a simple feature count.

Pool fit and cleaning reach

Both robots are intended for inground pools. Both are rated for pools up to 50 ft. Each cleans floor, walls, and waterline, so coverage alone does not separate them. Dolphin M550's documented cleaning system includes 2 active brushes and CleverClean navigation.

Filtration and debris

Both models include Basket and UltraFilter. Both have documented fine-debris media, so basket capacity and ease of cleaning matter more than fine-particle capability.

Controls and day-to-day ownership

Dolphin M550 provides a weekly timer and smartphone control; Dolphin T55i provides a weekly timer, smartphone control, and included remote control. Dolphin M550 uses continuous corded power, while Dolphin T55i uses a 60 ft corded cable with an anti-tangle swivel.

Price, warranty and the decision

Dolphin M550 is listed at $1,999 and Dolphin T55i at $1,699; Dolphin T55i is $300 less. Dolphin M550 lists a 3-year warranty compared with 2 years for Dolphin T55i. Dolphin M550 and Dolphin T55i each have a specific fit, but neither is the Pool Express pick for this job. Our better alternative is Dolphin Quantum. Inground pools up to 50 ft that need floor, wall and waterline cleaning, with fine debris.

Feature check: what each robot actually has

A green check means the feature is documented as included. A red X means it is documented as absent. A dash means the source does not make the feature clear.

Feature	Dolphin M550	Dolphin T55i
Cleans the pool floor	Yes	Yes
Climbs and cleans walls	Yes	Yes
Scrubs the waterline	Yes	Yes
Fine-debris filter included	Yes	Yes
Large-debris filter	Yes	Yes
Automatic scheduling	Yes	Yes
Smartphone app	Yes	Yes
Anti-tangle swivel	Yes	Yes
3-year warranty	YesEdge	No
No recharging between cycles	Yes	Yes
Built-in UV-C water treatment	No	No

Unknown is not treated as “no.” Specifications come from the product pages, current catalog records and manufacturer material collected for this site.

Where Dolphin M550 stands out

Dolphin M550 is the better fit for inground pools up to 50 ft that need floor, wall and waterline cleaning with app control, Pick-Up and a caddy.

Carries a 3-year warranty instead of 2 years
2-hour cycle, pools up to 50 ft

Where Dolphin T55i stands out

Dolphin T55i is the better fit for shoppers prioritizing the lower $1,699 starting price.

Is listed $300 lower
60 ft cable with anti-tangle swivel