ComModule - Connect your WaterRower!

ComModule - Connect your WaterRower!

Ross Arnott Ross Arnott
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The WaterRower is one of the most popular rowing machines due to its stylish appearance and the relaxing sound of water resistance.  Most WaterRowers come with the Series IV (S4) Performance Monitor as standard, which is great for displaying your stats, but isn't able to wirelessly connect to your phone via Bluetooth.  The WaterRower ComModule accessory for the S4 Monitor solves that, allowing your rowing machine to connect to almost any smart device via Bluetooth opening up a world of apps that can enhance your rowing experience through coaching, tracking and challenges.

What Is The ComModule for WaterRower S4?

The commodule from WaterRower is an attachment that plugs into the rear of your WaterRower Series IV (S4) monitor that adds Bluetooth capability and allows wireless connection to a smart device, opening up a world of connectivity and interactive apps such as asensei, WaterRower connect and services such as Strava and Apple Health. The ComModule is an official aftermarket accessory made and sold by WaterRower and it comes in a compact form factor that clips to the back of your S4 monitor, connecting to it via the USB mini port on the Monitor. The ComModule is the easiest and cheapest way to upgrade your WaterRower to become a connected fitness device!

WaterRower ComModule rear view

The ComModule add-on for the WaterRower S4 monitor

How Do You Buy a WaterRower ComModule?

The easiest way to buy a ComModule upgrade for your Waterrower is through the official WaterRower websites.  



Is the ComModule Currently In Stock?

Supply chain issues which have affected many companies mean that, at the time of writing, the ComModule availability is showing as limited so if you see one and you have decided you need it, we'd recommend you don't hesitate to go ahead and buy it! 

Third Party ComModule Sales 

3rd party resellers of the ComModule may be able to help when stock is limited on the official WaterRower sites, but do take care if you are unfamiliar with the seller.

How Do You attach a ComModule to a WaterRower?

To attach a ComModule to a WaterRower S4 monitor is quite simple, and WaterRower make it easy by providing all of the tools required when you purchase. 

Step 1. Remove the Battery Cover on the S4 performance monitor. 

To remove the existing S4 monitor battery cover means unscrewing the two screws that hold it in place.  Your new ComModule comes with a crosshead screwdriver for exactly this purpose.  When the screws are undone simply lift the cover off, being careful not to lose the small screws.

waterrower S4 monitor with old battery cover and commodule battery cover

Waterrower S4 monitor with old battery cover, replacement ComModule battery cover and supplied screwdriver

Step 2. Attach the new battery cover that comes with the ComModule. 

The new cover is shaped to allow the ComModule to clip onto the S4 monitor and will help hold it in place securely.  Simply fit the new cover over the battery compartment (you might want to check the batteries don't need replaced before you do this) and use the two crosshead screws to secure it into position.  

WaterRower commodule viewed from a side angle

WaterRower ComModule side angle view - showing the charging port

Step 3. Attach the comModule to the rear of the Series IV Monitor. 

You may need to remove the cover from the USB port in the top right of the rear of the S4 Monitor and slide it round to the side so it does not get in the way.  Or you can pull it out entirely if you don't expect to need it again.  Then you simply line up the protruding male USB mini connector on the ComModule to the USB mini female port on the WaterRower

WaterRower S4 monitor with ComModule fitted, viewed from rear

WaterRower ComModule fitted to the Series IV Monitor

Charging a WaterRower ComModule

The ComModule contains a rechargeable battery of its own and needs to be charged periodically.  WaterRower reckon that a fully charged ComModule should give about 8 hours of usage. The Series 4 monitor batteries are completely separate and will still need replaced periodically as normal.

Charging is performed via a USB mini port on the side of the ComModule.  Because the USB mini connector is not the most common these days WaterRower supply the ComModule with a short USB-A to USB-mini cable.  WaterRower don't supply a charger with the ComModule, but the USB-A will plug in to many chargers, so this makes sense for environmental and cost reasons.

USB-A to USB mini cable for WaterRower ComModule

USB-A to USB mini cable for WaterRower ComModule

Unfortunately the USB mini connector can't be readily inserted while the ComModule is fully attached to the S4 monitor and you have to detach it first.  This is not an especially tricky task but it is a little annoying and some care should be taken to avoid damaging your ComModule. 

Note, if you pull the ComModule away from the S4 monitor a little you can just squeeze the USB cable in to the charging port without fully detaching, but this will put the connection to the S4 Monitor under some stress, so care should be taken if doing this.  You'll also likely need a longer charging cable than the one supplied unless your WaterRower is located close to a charging point or you are using an extension cable.

Side image of the WaterRower S4 Monitor with ComModule attached - showing USB mini charging port.

Side image of the WaterRower S4 Monitor with ComModule attached - showing USB mini charging port.

What Apps Connect to a WaterRower via the ComModule?

It's possible to connect a number of apps to the WaterRower via the ComModule. The WaterRower with ComModule shows up as an FTMS (Fitness Machine Service) device in Bluetooth, which is a standard protocol, so many apps are capable of connecting. Ideally you should choose an app that has been optimized to work with the WaterRower so that connection and workout experiences are seamless - those specific WaterRower apps include asensei and WaterRower Connect.  

Does WaterRower Connect to asensei?

The WaterRower can be connected to the asensei app to bring great interactive workouts and connected coaching to your rowing machine.  Before you start you need to ensure the ComModule is connected to your Series IV monitor and that the monitor is turned on.  Then open the asensei app, start a workout and press the button on the top of the ComModule, which will flash blue until it automatically connects to your smart device running the asensei app. From there you just enjoy your asensei workout which will track your progress, set you personalized goals and give you coaching from some of the worlds best coaches.

The asensei app is rated 4.8 stars in the iOS appstore and is the top rated rowing app available.  asensei is free to download and try, including a number of free workouts from a range of different coaches such as Olympic Champion Eric Murray, British Rowing and studio fitness coach Johan Quie. 

With a subscription to the asensei app you can gain access to the Embark: Start Rowing with WaterRower program which gives an introduction to the WaterRower rowing machine (with ComModule), basic technique and a range of different types of rowing workouts.

How do you learn good rowing technique with a WaterRower ComModule?

When you use an app such as asensei you access a world of video coaching from some of the finest athletes and coaches in the world, such as Champion rower and world record holder Eric Murray.  The structured programs include detailed video and audio coaching, while you workout, so that you learn great technique which helps you row faster, prevents injury and increases your enjoyment.  By tracking your progress during a training program asensei can see your improvement and will set you goals according to your capabilities.

Can You Follow a Structured Training Plan with the WaterRower ComModule?

When you connect your WaterRower to a smart device via a ComModule you enter a world where training programs are easy to follow and can be tailored and personalized to meet your fitness goals.  With apps like asensei you won't have to program the monitor, calculate your pace goals or track your results - it's all done for you.  To find out more about the type of programs on offer to help you hit your fitness goal check out: Our favorite indoor rowing training programs

How Does WaterRower Connect Work?

The WaterRower Connect app requires the S4 monitor with the ComModule installed and then provides basic workout and tracking functionality.  In the app you can set a time-based workout, a distance based workout, an interval workout or a free rowing workout via the WaterRower Connect app.  This won't program the monitor, but will display details on your phone screen.   The app also has the ability to see an overview of your workout history.  The WaterRower Connect app is rated as 4.1 stars in the Apple appstore.

Features such as structured workout programs are available via the subscription only WaterRower Connect Premium service. 

Where can I find out more about WaterRower apps?

To find out more about WaterRower apps we suggest you take a look at this detailed comparison article What's the Best App for WaterRower which covers the most popular applications, what people enjoy about each and what they don't love so much.  For anyone who wants to get connected and start tracking and training with great coaches it's a great resource.


The ComModule is the easiest and cheapest way to add Bluetooth Functionality to your WaterRower with S4 Monitor.  It can be connected to your rowing machine in minutes and you will immediately be ready to run a connected workout.  With apps like asensei you will never have to bother with choosing a workout, programming the monitor, tracking your result, figuring out target pace and you'll be able to access structured training programs with great technique coaching. 

Frequently Asked Questions

Answers to a number of additional ComModule related questions

Can WaterRower Connect To Strava?

It is possible to connect your WaterRower to Strava but you must have the Bluetooth ComModule installed first and the connection to Strava will be via another app such as WaterRower Connect.  

How Do You program a WaterRower?

Normally a WaterRower is programed via the S4 monitor where you can set the distance, time and workout zones for your workout.  The video below includes some details of how to program workouts.

You will notice that programming the monitor can be a little fiddly, particularly for complex workouts.  Luckily, when you are connected to an app such as asensei, you don't have to bother programming the S4 Monitor, asensei takes care of all of the intervals and tracking within your app, meaning you only need to turn the monitor on at the start and the rest is done for you!  It's not actually possible to program the Monitor via the ComModule since it only transmits the data from the rowing machine, it doesn't allow configuration of the monitor, so bluetooth connected apps like asensei display your workout timings, interval breakdown, split times etc directly on your phone/tablet screen instead, while the monitor just runs continuously.

Find out more

The S4 monitor instruction manual contains further details of how to program advanced workouts.

Does WaterRower have Bluetooth?

WaterRowers do not currently come with Bluetooth capability built into their hardware as standard in the same way as some rowing machines do.  While there are a number of different types of monitors that come with the WaterRower such as the A1 and the Series IV (S4), only the Series IV monitor can be upgraded to use the ComModule addon, which is the WaterRower Bluetooth module.

Does WaterRower Series IV Have Bluetooth?

The WaterRower Series iV monitor does not come equipped with Bluetooth capability by default.  The only current way to get Bluetooth connectivity with a WaterRower S4 monitor is to use the ComModule which is an aftermarket WaterRower Bluetooth Hardware attachment.

ComModule vs SmartRow

In addition to the ComModule there is another way to connect your WaterRower to a smart device and that's via the SmartRow conversion kit for WaterRower.  The SmartRow upgrades the WaterRower with additional, more accurate metrics, such as force curves that make it more similar to a Concept 2.  The SmartRow requires modifications to the WaterRower rowing machine itself and replaces the S4 monitor altogether.  As a result if you already have a WaterRower then this route to Bluetooth connectivity is considerably more expensive, costing $275 at the time of writing, vs $59.95 for the ComModule (prices may vary).

The WaterRower+SmartRow comes with a companion app called Smart Row which allows you to view the additional metrics, such as Force Curves.  Currently rated at 3.7 stars on the appstore, this app has not been updated for approximately 8 months.

It should be noted that the WaterRower with SmartRow will not connect to the same apps as the ComModule WaterRower Bluetooth Hardware so do check carefully before purchase.  For example the asensei app does not currently connect to the WaterRower. 

3rd party SmartRow apps require two smart devices, one to run the SmartRow app and one to run the 3rd party app.

Is there a WaterRower Bluetooth Monitor that doesn't require a ComModule?

There have been rumours of a new WaterRower monitor with built in Bluetooth capability for some time, however at the time of writing this was not available to buy.  The rumors have suggested this could be called the Series 5 Monitor, but we expect this to now be named as Series 4 with BLE (Bluetooth Low Energy ) capability.  We will keep this article updated if that changes!

The latest version of the asensei app has been updated to be compatible with the WaterRower S4 Bluetooth monitor which we expect to be released before the end of 2022. 

Can You Control the WaterRower S4 Monitor via the ComModule?

While it might be nice for the WaterRower S4 monitor to be controlled by your smart device, this is not currently possible via the ComModule, for the reason that the USB port into which it plugs does not allow control over the S4 monitor.  The workout data comes out via this USB port, but currently you can't send control information back in by this route.  This means that any apps that make use of the ComModule can't change what is displayed on the S4 monitor, so you must rely on the data that is shown by the app.

What is the FTMS Protocol used by the WaterRower ComModule?

The WaterRower with ComModule communicates using the FTMS (Fitness Machine Service) device in Bluetooth, which is a standard protocol designed to allow Fitness Machines like your WaterRower to connect to compatible fitness applications. 

While FTMS is a standard and supports rowing machines as well as a range of other equipment like stationary bikes and treadmills, there is also scope for quite a lot of variation in the way each manufacturer implements it.  So for example the WaterRower with ComModule isn't configurable via the FTMS protocol, it only transmits data.  And the data that it sends is not as extensive as say a SmartRow device.


asensei is free to download and with no commitment you can trial the first 3 workouts in the (RE)COMMIT program and also workouts from MASTER THE BASICS, (RE)FOCUS, SWEAT FACTORY and BE A DARK HORSE.

All you need is an iPhone or iPad and access to an asensei Compatible rowing machine from Concept 2, WaterRower or FluidRower with a bluetooth capable monitor.

download asensei from the appstore



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