Help me choose
Our pick: Dolphin Sigma
Dolphin Sigma is the Pool Express pick in this matchup. Dolphin Sigma is rated for pools up to 50 ft. Dolphin Sigma runs from continuous plug-in power without a recharge between cycles.
ProLine
Dolphin Sigma
Inground pools up to 50 ft that need floor, wall and waterline cleaning, with fine debris.
Liberty
Dolphin Liberty 400
Inground and above-ground pools up to 33 ft that need floor, wall and waterline cleaning without a cord.
Why Dolphin Sigma is our pick
Dolphin Sigma
Inground pools up to 50 ft that need floor, wall and waterline cleaning, with fine debris.
$2,399
Buy Dolphin SigmaDolphin Sigma or Dolphin Liberty 400: our take
Dolphin Sigma and Dolphin Liberty 400 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 Sigma is intended for inground pools, while Dolphin Liberty 400 is intended for inground and above-ground pools. Dolphin Sigma is rated for pools up to 50 ft; Dolphin Liberty 400 is rated up to 33 ft. Each cleans floor, walls, and waterline, so coverage alone does not separate them. Dolphin Sigma's documented cleaning system includes 2 active brushes, SmartNav 3.0 with gyroscope navigation, and Triple commercial-grade DC motors.
Filtration and debris
Dolphin Sigma includes Standard filter and NanoFilters; Dolphin Liberty 400 includes Basket and UltraFilter. Both have documented fine-debris media, so basket capacity and ease of cleaning matter more than fine-particle capability. Dolphin Liberty 400 has the better documented path for bulky leaves and larger debris.
Controls and day-to-day ownership
Dolphin Sigma provides a weekly timer, smartphone control, and included remote control; Dolphin Liberty 400 provides a weekly timer and smartphone control. Dolphin Sigma uses a 55 ft corded cable with an anti-tangle swivel, while Dolphin Liberty 400 uses cordless battery power. Dolphin Sigma is listed at 24.6 lb versus 17.9 lb for Dolphin Liberty 400; that 6.700000000000003 lb difference matters when lifting the robot from the pool.
Price, warranty and the decision
Dolphin Sigma is listed at $2,399 and Dolphin Liberty 400 at $1,429; Dolphin Liberty 400 is $970 less. Each lists a 3-year manufacturer warranty. Pool Express pick: Dolphin Sigma. Dolphin Sigma is rated for pools up to 50 ft. Dolphin Sigma runs from continuous plug-in power without a recharge between cycles. Choose Dolphin Liberty 400 when it is the better fit for shoppers prioritizing the lower $1,429 starting price.
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 Sigma | Dolphin Liberty 400 |
|---|---|---|
| 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 | No | YesEdge |
| Automatic scheduling | Yes | Yes |
| Smartphone app | Yes | Yes |
| Anti-tangle swivel | Yes | Not listed |
| 3-year warranty | Yes | Yes |
| No recharging between cycles | YesEdge | No |
| 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 Sigma stands out
Dolphin Sigma is the better fit for pools up to 50 ft.
- Is rated for pools up to 50 ft
- Runs from continuous plug-in power without a recharge between cycles
Where Dolphin Liberty 400 stands out
Dolphin Liberty 400 is the better fit for shoppers prioritizing the lower $1,429 starting price.
- Includes a large-debris bin or bag for leaves
- Is listed $970 lower
- Weighs 17.9 lb versus 24.6 lb
Dolphin Sigma vs Dolphin Liberty 400 specifications
Use pool fit first. Price and app control do not make up for a robot that cannot cover the length or surfaces you need cleaned.
| Specification | Dolphin Sigma | Dolphin Liberty 400 |
|---|---|---|
| Best fit | Inground pools up to 50 ft that need floor, wall and waterline cleaning, with fine debris. | Inground and above-ground pools up to 33 ft that need floor, wall and waterline cleaning without a cord. |
| Starting price | $2,399 | $1,429 |
| Pool type | Inground | Inground, Above-ground |
| Maximum pool length | Up to 50 ft | Up to 33 ft |
| Cleaning coverage | Floor, Walls, Waterline | Floor, Walls, Waterline |
| Power | Corded | Cordless |
| Filtration | Standard filter, NanoFilters | Basket, UltraFilter |
| Scheduling | Weekly schedule + app | Weekly schedule + app |
| App and remote | App + included remote | App control |
| Cable | 55 ft with anti-tangle swivel | Cordless |
| Robot weight | 24.6 lb | 17.9 lb |
| Warranty | 3 years | 3 years |
Choose Dolphin Sigma
Dolphin Sigma is the Pool Express pick in this matchup. Dolphin Sigma is rated for pools up to 50 ft. Dolphin Sigma runs from continuous plug-in power without a recharge between cycles.
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