Robotic pool cleaner comparison

Dolphin S100 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 S100 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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S-Line

Dolphin S100

Inground and above-ground pools up to 33 ft that need floor and wall cleaning, with fine debris.

Listed price $849

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T-Line

Dolphin T55i

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

Listed price $1,699

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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 S100 or Dolphin T55i: our take

Dolphin S100 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

Dolphin S100 is intended for inground and above-ground pools, while Dolphin T55i is intended for inground pools. Dolphin S100 is rated for pools up to 33 ft; Dolphin T55i is rated up to 50 ft. Dolphin S100 cleans floor and walls; Dolphin T55i cleans floor, walls, and waterline. Dolphin S100's documented cleaning system includes 1 active brush.

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 S100 provides a weekly timer and power-supply controls; Dolphin T55i provides a weekly timer, smartphone control, and included remote control. Dolphin S100 uses a 50 ft corded cable, while Dolphin T55i uses a 60 ft corded cable with an anti-tangle swivel.

Price, warranty and the decision

Dolphin S100 is listed at $849 and Dolphin T55i at $1,699; Dolphin S100 is $850 less. Each lists a 2-year manufacturer warranty. Dolphin S100 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 S100	Dolphin T55i
Cleans the pool floor	Yes	Yes
Climbs and cleans walls	Yes	Yes
Scrubs the waterline	No	YesEdge
Fine-debris filter included	Yes	Yes
Large-debris filter	Yes	Yes
Automatic scheduling	Yes	Yes
Smartphone app	No	YesEdge
Anti-tangle swivel	Not listed	Yes
3-year warranty	No	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 S100 stands out

Dolphin S100 is the better fit for shoppers prioritizing the lower $849 starting price.

Is listed $850 lower
Cleans floor and walls

Where Dolphin T55i stands out

Dolphin T55i is the better fit for pools up to 50 ft.

Cleans the floor, walls and waterline instead of stopping below the tile line
Adds smartphone control
Is rated for pools up to 50 ft