Dolphin M400 vs Sigma: Features, Filtration and Price Compared

By John, Dolphin pool cleaner repair technician at Pelican Shops Morris Plains · Updated October 29, 2026

The Dolphin M400 and Sigma have a lot in common. Both are corded robotic cleaners with the features many inground pool owners are looking for. Their similarities make the differences in brushing, price and service especially worth understanding.

I am John, a Dolphin pool cleaner repair technician at Pelican Shops Morris Plains. When I compare cleaners, I look at their equipment, features, the parts we work with and what ownership involves. This comparison brings those details together with our pricing and Dolphin’s published specifications.

Dolphin M400 vs Sigma: side-by-side specifications

Sources: Dolphin M400 technical specifications, Dolphin Sigma technical specifications and our comparison chart.

The active scrubber is the clearest hardware difference

The M400 has an active brush; the Sigma does not. That distinction can get lost when both descriptions talk about scrubbing.

A normal brush still contacts and brushes the surface. An active scrubber adds faster brushing action. Dolphin explains that certain active brushes rotate at twice the robot’s travel speed to help loosen debris for collection. Having brushes and having an active brush describe different mechanisms.

Source: Dolphin’s explanation of its brushes.

Does the Sigma really have “commercial-grade” motors?

Some resellers describe the Sigma as having “commercial-grade” motors. That wording suggests you are getting upgraded motor hardware that sets it apart from residential models like the M400. As a Dolphin repair technician, I can check that claim against the parts catalog.

The dealer parts listings show the same motor unit for the residential M400 and the Sigma: 99953054-EX. Both identify the same motor assembly. The catalog does not identify a separate, upgraded commercial motor unit for the Sigma in these listings.

• Dolphin M400: cleaner SKU 99991053-USI → motor unit 99953054-EX.
• Dolphin Sigma: cleaner SKU 99991036-SPLI → motor unit 99953054-EX.

Dealer parts-catalog evidence: the Sigma uses the same listed replacement motor assembly as the residential M400. Dealer costs are redacted.

That is why I treat the Sigma’s “commercial-grade motors” description as reseller marketing rather than a documented motor upgrade. Dolphin does not make that claim on the Sigma product page linked here. Maytronics lists the Sigma in its residential range and identifies the Wave line on its commercial-cleaner pages.

The catalog evidence challenges the suggestion that the Sigma has special commercial motor hardware unavailable in the M400. Sharing a part does not establish the duty rating of that component, but it does mean the reseller wording is not evidence of a different motor assembly. The higher advertised Sigma price does not buy a separate motor unit in these listings. So you need to be careful to not overpay for A dolphin Sigma. The MSRP is $1,599 and that is the most you should pay. Not what these sellers are selling it for currently.

Sources: our dealer-portal screenshots above, Dolphin Sigma specifications, Dolphin motor-replacement support and Maytronics commercial cleaners.

Gyroscope technology is not exclusive to the Sigma

A feature does not become exclusive because it receives more attention in one model’s advertising. The Sigma’s gyroscope is often highlighted, but gyroscope-based navigation is also used elsewhere in the Dolphin range, including the M400.

For this comparison, the relevant question is what separates the two cleaners. A shared navigation technology does not explain the additional asking price.

Filtration and routine maintenance are similar

Our chart identifies cartridge filtration on both the M400 and Sigma. Both provide access from the top, and the compared packages include fine and ultra-fine media. IMPORTANT NOTE: Some sellers will use the term nano filters. This is just another name for dolphin's ULTRA FINE FILTERS. We reccomend looking at dolphins direct site maytronicsus.com to confirm this. You will never see the term nano filter used on their site. only Ultra fine or fine filters. 

The cartridge design is a similarity between these two machines. 

MSRP and the online selling price tell different stories

Our 2026 chart lists the M400 at $1,649 MSRP and Sigma at $1,599 MSRP. On those reference figures, the M400 is $50 more expensive. At that difference, the active scrubber and the service included with an eligible Pelican purchase are tangible additions to consider.

The M400 also often qualifies for seasonal rebates, while the Sigma does not. An eligible rebate can reduce the M400’s effective cost further. Availability, purchase dates and redemption requirements depend on the promotion; the price differences below are calculated before any rebate.

The comparison changes when the Sigma’s advertised selling price is $2,399. That is $800 above our Sigma MSRP reference and $750 more than the M400’s $1,649 Pelican price.

At the $2,399 advertised price, the specifications and matching motor-unit listing do not establish an equipment advantage that justifies the extra $750. The Sigma does not gain higher rated flow, a longer manufacturer warranty or an active brush for that additional money. The M400 is sold at our chart MSRP, while that Sigma listing is $800 above its $1,599 MSRP reference.

What comes with an eligible Pelican purchase?

We have our own Dolphin repair technicians at Pelican. For eligible M400 purchases, our enhanced warranty program includes covered repair labor during the manufacturer warranty period and shipping to and from Pelican for the first two qualifying repairs in the mainland United States.

Full details are in our enhanced warranty terms.

What the comparison shows

At their chart MSRP figures, these cleaners are separated by $50. At the advertised prices compared here, the Sigma costs $750 more. The dealer parts catalog shows the same motor-unit part number, and the compared specifications show equal rated flow and manufacturer warranty length. Meanwhile, the M400 adds the active scrubber and eligible Pelican service benefits. That leaves no documented motor upgrade to account for the Sigma’s higher advertised price.

That is the value of laying the equipment and prices out together. A higher online asking price and stronger marketing language do not add hardware to the machine.

For ordering information, view our Dolphin M400. You can also use our full comparison chart or call me and our robot team at 973-313-4424 for help with your pool and order.

Updated October 29, 2026. This article combines manufacturer specifications, our comparison chart and dealer motor-unit screenshots and repair-parts knowledge. Prices, packages and promotions can change.