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Includes a center 2×-speed active scrubbing brush between front and rear rollers.
4,500 GPH Heavy Suction
Dual-drive M-Series torque climbs vertical walls and scrubs waterlines up to 50 ft.
myDolphin™ Plus Wi-Fi App
Weekly scheduling and manual directional steering from your phone.
Dual Top-Load Cartridges
Includes both spring mesh and ultra-fine pleated filter sets.
60-Ft Anti-Tangle Swivel
Keeps the floating cable twist-free across 2.5-hour cycles.
3-Year Maytronics Warranty
Maytronics' longest residential coverage tier.
The Bottom Line
Where the Dolphin M400 Fits
Best For
50-ft inground pools comparing classic M400 triple-brush scrubbing against the newer M600 and ProLine™ flagships.
What We’d Buy
A classic triple-brush M-Series cleaner. M600 offers a newer Multi-Layer basket, Pick-Up Mode, and an included caddy.
M400 or Newer M600?
The Dolphin M400 uses Maytronics' classic twin-cartridge frame and triple-brush setup. The Dolphin M600 moves to one Multi-Layer top-load basket, adds Waterline Pick-Up Mode, weighs less, and includes the Universal Caddy. Both carry 3-year Maytronics coverage.
The Dolphin M400 is a corded robotic pool cleaner from Maytronics, rated for in-ground pools up to 50 ft long. It cleans the floor, walls & waterline on a 2.5-hour default cycle, using 3 brushes, with a rated suction of 4,500 GPH.
Filtration is a fine filter kit with top access, and an ultra-fine filter kit is included in the box. It has a weekly timer, and it connects to the MyDolphin™ Plus app. The cable has an anti-tangle swivel. The robot weighs 27 lb and carries a 3-year Maytronics warranty.
Experience next-level cleaning with the M400, purposefully crafted for deeper pools.
Maytronics, on the Dolphin M400
Specifications
Dolphin M400 Specs
Product Attributes
Maximum Pool Length
50 ft
Cleaning Coverage
Floor, Walls and Waterline
Default Cycle Time
2.5 hours
Warranty
3 years
Delay Feature
No
Weekly Timer
Yes
Mobile Application
MyDolphin™ Plus
Anti Tangling Swivel
Yes
Additional Filter in the Box
Ultra-Fine Filter Kit
Filter Type
Fine Filter Kit
Cleaning
Filter Access
Top Access
Full Filter Indicator
No
Waterline Scrubbing
Yes
Enhanced Cleaning Cycles
No
Active Brush
Yes
Number of Brushes
3
Brush Type
Standard Brush, Combine Brush
Suction Rate
4,500 GPH
Connectivity & Automation
Automation Mode
Yes
Pool Attributes
Pool Shape
Rectangular, Round, Free Shape, Kidney
Pool Classification
In Ground
Size & Dimension
Package Dimensions
23.3x19.4x13.7 in
Robot Weight
27 lb
Net Height
10.7 in
Net Length
16.8 in
Net Width
16.2 in
Other
Remote Control
No
Specifications as published by Maytronics for product no. 99991053-USI (UPC 810071222016).
FAQ, Manuals & Parts
Dolphin M400 FAQ & Owner Support
Frequently asked questions
Straight answers on parts, ownership, and the closest models you can order today.
Dolphin M400 vs. Dolphin M600—which is better?
The Dolphin M600 ($1,799) is a newer-generation architecture that replaces two older cartridge doors with one nested Multi-Layer basket, adds Waterline Pick-Up Mode, and includes the Universal Caddy—for just $50 over M400 list.
Which replacement power supply fits the Dolphin M400?
Maytronics' own fixes for the problems owners report most, followed by the symptom table from the user manual.
MyDolphin Plus Wi-Fi Connectivity Guide
Maytronics MyDolphin™ Plus application, connected via the Cloud, allows you to control your Dolphin robot from anywhere, at any time, thanks to real-time connectivity.
Here is a quick video to make your first connection easy!
Compatibility
Apple (iOS): version 10 or later / iPhone, iPad, iPod
Android: operating system version 5 or later
Wi-Fi Network Requirements
Transmitting the 2.4 Ghz frequency only
Network password of less than 32 characters, without spaces and special characters (i.e., # % & " $ ￡)
A signal strength at the location of the power supply unit that is at least 60%, i.e., 2 out of the 3 possible bars.
If your Wi-Fi® network's technical specifications do not allow this connection, you can also connect to your Dolphin robot via Bluetooth® only.
Getting started with the MyDolphin™ Plus App
Ensure that your smart mobile device is connected to your Wi-Fi® network and that your signal strength is at least 60% at the location of the power supply, i.e. 2 bars out of 3.
Verify you have the name and password of your Wi-Fi® network available (the password must be less than 32 characters).
Make sure Bluetooth® is enabled on your phone or tablet.
For Android users: Please make sure that your GPS and location-based services are turned ON.
For iOS 13 users only: You must allow the application to use Bluetooth® and location-based services while the application is running.
Preparing your Dolphin to establish the connection
Connect the power supply unit to an electrical outlet and the blue cable on the Dolphin robot to the power supply unit.
The power supply connectivity LED will start flashing blue.
Place the Dolphin in the water.
Press the power supply unit on/off button to start the cleaning cycle of your Dolphin.
Connecting your Dolphin to your phone/tablet
Launch the MyDolphin™ Plus app.
Click Accept and grant access to all required permissions.
Sign up by creating an account or use your Gmail/Facebook/Apple account.
Scan the QR code on the side of the power supply unit, or press "Search manually" to establish the connection with your robot. "Search manually" will appear under the QR scanner. The application will start pairing with your power supply once the robot is found via Bluetooth®.
Wait until the connectivity LED is solid blue and a success message shows in the application.
The application will now ask you to connect to your Wi-Fi network.
Verify that the name of your Wi-Fi network appears in the Wi-Fi network name field.
Type in the password (which must be less than 32 characters) for your Wi-Fi network, and press Continue.
Wait a few moments, because this might take up to 2 minutes, depending on the signal strength of your Wi-Fi network. During this process, your power supply LEDs will flash between green and blue.
Wait until the connectivity LED is solid green and a success message is displayed in the application.
First Bluetooth® Connection
Please verify that you have granted all permissions when signing up on the app (location / BLE / etc.) and that all conditions are met (Wi-Fi / Cellular / BLE).
Please make sure that the blue cable is properly connected to the PWS.
When trying to connect, does a picture of the robot come up?
If no robot is shown, please reach out to our Customer Care team here with a screenshot of the step you are stuck in.
You have now successfully paired your robot to the app!
You can now give your Dolphin a name, register its warranty, and enjoy the app's features.
Stuck on Loading screen:
The connection process is divided into three stages. Percentages represent these stages. If the app is stuck on one of these percentages, this can indicate a specific issue.
First Stage – 0-10% / Sending WIFI info to the power supply (phone-power supply)
After the initial Bluetooth® connection, the app sends Wi-Fi details from the phone to the power supply. If it is stuck at this percentage, the connection was cut or not sent properly.
Close the app, reopen it, and try reconnecting, standing close to the power supply to ensure connection. Also verify that the Wi-Fi network’s name is correct and that there are no foreign letters or characters.
Second Stage – 10-50% / Power supply is connecting to the router
This stage is checking the Wi-Fi network requirements (2.4 GHz), this will take up to two minutes.
Verify that the network requirements are correct if stuck on this stage.
Third Stage – 50-90% / Power supply is connecting to cloud
If the connection fails here, it is because there is an issue with the cloud/connection to the cloud.
Reset the router.
The MyDolphin Plus app works with WPA/WPA2-Personal & WPA2/WPA3-Personal.
Note - It is not possible to purchase a Wi-Fi-compatible power supply and pair it with a non-Wi-Fi robot to use the MyDolphin Plus app.
Refer to the user manual to verify if your Dolphin model is compatible with the MyDolphinPlus app.
Still need assistance? Click the blue chat icon in the bottom-right corner of your screen to start a conversation with our AI agent — 'Phin'!
My Dolphin does not complete a cycle / Red light on the Power Supply
Click here to use our easy-to-use self-service tool to troubleshoot your robot and complete a warranty claim for repair or power supply replacement.
If the robot was purchased through a local dealer, please verify if they provide repair services.
If your Dolphin robotic pool cleaner starts the cycle but does not complete or stops shortly after, or the Power Supply shows a red light (this means there is an error with the robot), follow these troubleshooting steps to try and resolve the issue:
Note: Before turning the robot on, it must be submerged in at least three feet of water.
4. Check the PowerStream (Selected Models only) (click here for steps)
If your robot model has a Power Stream mobility system (located on top of the Impeller), please check the plastic cover around the motor unit and the grilles on the sides of your model for visible debris and remove the debris.
Want to talk to a real person? Our Customer Care Team is here for you—just give us a call at 1-888-365-7446 / 1-855-634-8572! The Customer Care hours are Monday-Friday 8:00 am-5:00 pm EST
My Dolphin doesn't climb the walls or move sideways on walls
Click here to watch our Dolphin Tips video for step-by-step troubleshooting!
The robot should be used in water temperatures of 6°C - 35°C for optimal results. A low pool temperature can significantly hinder the robot's ability to climb. The water temperature should be maintained at a level higher than 15°C.
Checking Chemical Levels
Next, verify that the pool chemicals are within the recommended range. If the pH levels are too high or too low, this can affect the robot's climbing ability.
Additionally, if your robot has a fast mode or "Floor Only" mode, (only for models compatible with the MyDolphin/MyDolphin™ Plus app or with the power supply unit) verify that these modes have not been set.
Inspecting the Filters
It is imperative to check the filters. If you are using the Ultra-Fine (paper) filter, it should appear white. If the filter is brown or green, clean it with a garden hose set to the highest pressure. If the filter does not return to a white state– it is likely due to be replaced.
If you are using the Ultra-Fine filters, operate the robot with the Net Filters instead. If the robot is able to climb, this serves as an indication that the Ultra-Fine filters require replacement.
Debris in the Impeller
Make sure there is no debris obstructing the impeller. For instructions on how to clean your impeller, click here.
First, unplug the power supply from the outlet. Use a Phillips screwdriver, not a power drill.
If you notice debris trapped in the impeller, open it, remove the debris, and reassemble the impeller.
Does your robot have an adjustable handle? (Click Here)
Make sure the handle is aligned diagonally to help the robot climb.
For slow waterline cleaning (covers less surface area, but cleans more intensively): Put one end of the handle in the second/third slot, and the other end of the handle in the second/third slot (pictured above on the left side)
For fast waterline cleaning (covers more surface area, but cleans less intensively): Put one end of the handle in the first slot, and the other end of the handle in the fourth slot (pictured above on the right side)
Sufficient Cable Length
Ensure the robot has sufficient cable to allow it to climb the wall – the cable can pull the robot back if there is not enough of it.
To determine if you have the appropriate amount of cable in the pool, measure the cable length that matches your pool's longest dimension.
It is important to remember not to use an excessive length of cable to avoid tangling issues.
Brush Type
It’s important to use the correct brush based on your Dolphin model, the surface type and slopes of your pool.
PVC brushes are standard and work well for most pool floors.
Combined brushes (PVC with foam climbing rings) help the robot climb and grip better—if your robot has climbing rings, don’t remove them! They’re essential for performance and should be replaced when worn.
Wonder Brush is the ideal choice for ultra-smooth or slippery surfaces like stainless steel or polished mosaic tile.
If your robot struggles to climb walls or stay attached to the pool surface, switching to a combined brush might help.
If the robot is not cleaning the pool as it used to or is missing spots, we recommend verifying the following parameters.
Check that the chemical levels meet the following parameters:
Alkalinity: 80-120 ppm
pH: 7.2-7.6
Calcium Hardness: 150-250 ppm
Chlorine: 1.0-3.0 ppm
Cyanuric Acid: 30-50 ppm
Algaecide: 30-50 ppm
It is essential to maintain these levels for the best cleaning results and to preserve the robot's longevity.
The weather, our body chemistry, and additional factors can affect the chemical levels in the pool, therefore we recommend checking the chemical levels regularly. Click here to shop our pool chemicals
Check that the water temperature is between 43° - 95° Fahrenheit.
If your robot struggles to climb, ensure the pool temperature is higher than 59°F, as low temperatures can make it difficult for the robot to climb.
If there is a specific area in your pool that the robot is missing, we recommend putting the robot in that area from the start of the cycle.
If the robot is getting stuck in the deep end of the pool, it may be possible to upgrade the back brush on your robot to a Combined Brush or Wonder Brush. Please contact us here to verify if this solution will be suitable for your robot model.
What kind of debris is in the pool?
Depending on the type of debris there is in the pool, will help determine which filter type is most suitable for use.
If the debris is large debris such as tree foliage, we recommend using our fine (net) filters.
If the debris is sticky, algae-like debris, we recommend inquiring with your pool technician for further analysis and action.
If you complete a chemical shock, wait at least 24 hours after the treatment, before placing the robot back in the pool and verify that the chemical levels have returned to normal.
If there is a large amount of debris in the pool, we recommend running multiple cycles in a row and cleaning the filter after each cycle.
How does the robot filter look? Is it quite full? Could it be clogged?
We recommend using fine filter panels for large debris such as leaves and bugs, and ultra-fine filter panels for tiny debris such as dust, dirt, and sand.
Verify that the filters are not clogged and that the robot is free from debris, as clogged filters can interfere with the suction process and prevent the robot from picking up debris effectively.
First, unplug the power supply from the outlet. Use a Phillips screwdriver, not a power drill.
If you notice debris trapped in the impeller, open it, remove the debris, and reassemble the impeller.
Check your filter's non-return valve–the opening at the bottom of the filter–or the little black pouch attached to it and make sure it is free of debris.
Rapid drain flap
If applicable to your robot, make sure that the rubber rapid drain flap on the back of the robot is securely installed.
Why isn't the robot cleaning the debris on the steps/ledge/tanning shelf?
It is important to note that our robots are not designed to clean steps, stairs, or ledges. We recommend brushing the debris from the steps onto to the floor of the pool so that the robot can clean the debris.
Our robots require submersion in at least 35” of water to function properly.
If there is debris in the seam of a steep slope, we recommend brushing the debris from the seam onto a flat surface so that the robot will be able to reach the debris.
Important tips!
Make sure to put enough blue cable in the water to allow the cleaner to reach all areas in the pool.
It is important to make sure that the robot has a cable long enough to allow full coverage of your pool. You can measure the distance between the two farthest corners of the pool to get an understanding of the amount of blue cable needed. If your pool's length is over 30', make sure to use a robot with a cable length of 60'.
It is important to make sure that your robot's brush type is compatible with your pool coating.
If your pool has a PVC, concrete tile, concrete, or gunite coating, it is most compatible with a robot that comes with a PVC brush.
If your pool has a PVC, rough ceramics, fiberglass, or mosaic coating, it is most compatible with a robot that comes with a Combined brush (nylon should be removed before use).
If your pool has a smooth ceramic, stainless steel, or glass coating, it is most compatible with a robot that comes with a Wonder brush.
Special Considerations for Ultra-Fine Filters
It is important to note that if you are using ultra-fine filters, even if they appear to be clean, they may still be obstructed by tiny particles such as sand and dust. A useful tip is to observe the color of the filter:
If the ultra-fine filters do not wash out white anymore, this is a clear sign that they are indeed clogged, and we recommend replacing them.
Once your filters are clean, your robot will be able to clean more effectively.
Washing Bag Filters and Cartridge Panels
For bag filters, they can be washed in a washing machine at a temperature of 30 degrees Celsius, and it is advisable to let them air dry.
As for the filter cartridge panels, these can be cleaned in a dishwasher set to 30 degrees Celsius.
Click here to read more about the differences in the filter types.
Still need assistance? Click the blue chat icon in the bottom-right corner of your screen to start a conversation with our AI agent — 'Phin'!
My Power Supply Unit does not work properly
Click here to use our easy-to-use self-service tool to troubleshoot your robot and issue a warranty claim for a repair or power supply!
If the robot was purchased through a local dealer, please verify if they provide repair services.
Want to talk to a real person? Our Customer Care Team is here for you—just give us a call at 1-888-365-7446 / 1-855-634-8572! Between Monday-Friday 8:00 am-5:00 pm EST
Click here to watch our Dolphin Tips video for step-by-step troubleshooting!
If your Power Supply stops working, trips the GFCI outlet, or does not turn on at all, follow these troubleshooting steps to help diagnose and resolve the issue:
Step 1: Check the Power Source
Let's ensure that the issue is not originating from your home outlet. Try plugging the power supply into a different verified, working outlet or by disconnecting any extension cord that may be in use.
If the power supply still does not turn on, we can move on to the next step.
Step 2: Inspect the Blue and Black Cables
Examine the blue cable and the black power supply cord for any visible signs of damage, such as cuts, kinks, or frays.
If you find any cable damage, the cable should be replaced. Submit a warranty claim or visit your nearest dealer if you purchased from a local dealer.
If both cables appear to be in satisfactory condition and free from any damage, proceed to the next step.
Step 3: Determine the Source of the Issue
Now let's identify whether the problem lies with the Dolphin's Motor, the Cable(s), or the Power Supply itself. To do this:
Disconnect the blue cable from the Power Supply Unit.
Plug the Power Supply Unit into a functioning electrical outlet.
Now, turn on the Power Supply Unit without reconnecting the blue cable.
Step 4: Does the Power Supply Unit turn on and stay on?
After following the previous steps, does the Power Supply Unit turn on and stay on?
Click here, if it does!
If the Power Supply turns and stays on, the issue is not with the Power Supply. There may be an issue with the Dolphin's cable or motor unit.
An authorized Dolphin technician should analyze and repair the robot. Click here to submit a repair request or contact your local dealer (if you purchased the robot from a local dealer).
Click here, if the power supply doesn't turn on, or turns off immediately, or has stopped working altogether
It seems there is an issue with the Power Supply. Click here to create a warranty claim for a replacement power supply with our easy-to-use self-service tool!
Contact your local dealer if you purchased the robot from a local dealer for a replacement Power Supply Unit.
Power supply not connecting to Wi-Fi? Click here to read more.
Symptom
Possible reason
What to do
Power-supply or switch is not working.
• No voltage in the power socket in the wall. • The power supply is not switched ON. • Black power cable is not connected into the power supply inlet.
• Check that there is voltage in the power socket in the wall. • Check that the power supply is plugged in and turned ON. • Check that the power cable is securely connected all the way into the power supply. • Turn the power supply OFF. Wait 30 seconds, then turn it back ON.
Pool Cleaner does not move / Red light on the power supply.
• The blue floating cable is not connected into the power supply. • An obstacle is blocking the impeller, tracks or wheels. • Pool cleaner is out of water.
• Check that the blue floating cable is securely connected into the power supply. • Unplug the power supply. Open the impeller cover and check that nothing is trapped in the impeller. • Verify that nothing is blocking the tracks or wheels.
Pool Cleaner is moving in circles.
• Clogged filter. • Debris stuck in the impeller house or impeller cover. • Power supply incorrectly positioned. • Algae or pool water is out of spec.
• Clean the filter. • Remove debris stuck in the impeller house or impeller cover. • Place power supply in position so that the Pool Cleaner can freely reach all the pool area. • Correct pool and water conditions.
Pool Cleaner does not turn or moves in one direction only.
• Debris stuck in the impeller house or impeller cover.
• Remove debris stuck in the impeller house or impeller cover.
Pool Cleaner moves but does not clean the pool.
• Clogged filter. • Debris stuck in the impeller house or impeller cover.
• Clean the filter. • Remove debris stuck in the impeller house or impeller cover.
Pool Cleaner cleans only part of the pool.
• Power supply incorrectly positioned. • Not enough floating cable is released for the correct operation of the Robotic Pool Cleaner.
• Place the power supply in a position that enables the Pool Cleaner to freely reach the entire pool area. • Check there is enough slack in the blue floating cable for the Pool Cleaner to reach all of the pool. Clean the filter.
Blue floating cable has kinks.
• Clogged filter. • Debris stuck in the impeller-house or impeller-cover.
• Clean the filter. • Remove debris stuck in the impeller house or impeller cover. • To remove the kinks, stretch the floating cable out completely and let it sit for at least a day in the sun.
Pool Cleaner does not climb the walls.
• Clogged filter. • Algae on walls. • Unsuitable pH level. • Debris stuck in the impeller-house or impeller-cover.
• Clean the filter. • Check the level of chemicals in the water. Improper levels may allow the growth of algae, making the walls slippery. • Adjust chemical levels and scrub walls. • Remove debris stuck in the impeller-house or impeller-cover.
From the Dolphin M400 user manual's troubleshooting table.
This model next to the three ProLine™, Max-Series™ and Clear™ robots closest to its price. Use the dropdowns to put any robot in a column: every Dolphin line, the Clear™ Series, and the other brands we carry.
