Neptune Systems

1" Flow Sensor FS100

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$65.99 $65.99

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Know Your Flow!

1" Flow Sensor for the Fluid Metering Module from Neptune. 

The FS-100 will work with flow rates from 150-1500 gph, and will connect to any standard 1" Slip PVC.


Usually used with a return pump, this flow sensor can be placed in line with the flow on any pipe, connected to the FMM, and communicate to your Apex the flow rate of water through that pipe. The flow sensor itself uses British Standard Parallel Pipe (BSPP) threads so all BRS customers we have included two specially designed PVC unions with slip fittings to adapt it to standard 1″ PVC plumbing.


What's Included?

1x 1" Flow Sensor

2x BSPP x 1" Slip Unions


More Information
UPC 019962171550
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Product Questions

Do you have spigot adapters for these so I can use flexible pipe in and out and reduce the head pressure?
Question by: Dan Fain on Dec 18, 2023, 1:19 PM
Hey there, you can find those barbs here https://www.bulkreefsupply.com/gray-male-pipe-adapter-spigot-x-barb.html SKU:207927 Thanks!
Answer by: Codey on Jan 8, 2024, 2:10 PM
Can i use aquarium silicone to seal the entry where the cord makes contact? The unit is gonna be placed about 6 inches from water level in the sump, can it get wet? Reading others questions that pertain. How do i take it apart? Those screws on the face? Why are we still making aquarium equipment that isnt 100% waterproof? Seriously? I dont even want to see the flow meter and it takes up room so my idea was it to be in the return section of water.
Question by: Sean Hein on Jun 15, 2023, 7:19 PM
Flow sensors are water-resistant, and will withstand the occasional splash or drip. But they are not waterproof. For the best resistance to such splashes and drips, when installing, orient them so that the point where the cable enters the body of the flow sensor is pointing down if possible.

Don't take them apart. A good way to clean them is during a service, remove the sensor. Place the sensor in a bucket with Vinegar water solution. The solution should be filled to just below where the screws are. Do not submerge the screws.
Answer by: Scott F. (BRS Staff) on Jul 28, 2023, 10:35 AM
Hi, can this be used without purchasing the fmk kit? I have an FMM module on my Apex ATO. Can I just plug in to that? I really just need to monitor return flow for UV. Thanks.
Question by: A.C. Celik on Apr 26, 2022, 10:30 AM
Thanks for the question! The flow sensors just need an FMM module to connect to, the FMK is for those that don't already have one and want more than one sensor. Since you have the FMM you can pick up a sensor and connect it to the existing FMM.
Answer by: Kyle Thomas (BRS Staff) on Apr 26, 2022, 2:37 PM
Will BRS carry the replacement Union fittings for the FS-100 now that you all are partnered with Neptune?
Question by: David Holbrook on Dec 4, 2021, 11:21 AM
Thank you for your question. I spoke with our product team and they advised that we do not currently have plans to carry them but we may in the future. You can order replacement unions from Neptune by contacting them at 408-275-2205 or support@neptunesystems.com
Answer by: William Glenn (BRS Staff) on Dec 14, 2021, 2:51 PM
Can the 16' cord length be extended?
Question by: Marty on Nov 23, 2017, 8:26 AM
You could use a standard 1/4" headphone extension cable but you will want to make sure that it has the three black rings. Standard headphone jacks only have two rings, and the Neptune flow sensors do require the third ring for additional data to be sent.
Answer by: Charlie on Nov 24, 2017, 10:31 AM
The easiest place for me to add this would be at the end of my submerged return pump. Can you submerge the whole thing? Is it water proof or is it just water resistant?
Question by: Kevin on Oct 23, 2017, 2:59 PM
Hi Kevin, great question!

Do not submerge the FS100 flow sensor as it is not waterproof. According to the manufacturer, you should orient the sensor so that the point where the cable enters the body of the flow sensor is pointing down if possible. This will provide the best resistance to splashes and drips.

Please refer to Neptune's Flow Sensor installation guide for full list of tips and recommendations. https://forum.neptunesystems.com/showthread.php?18184-Flow-Sensor-Installation
Answer by: Nick on Nov 10, 2017, 1:15 PM
Does BRS plan to stock replacement BSPT fittings for these? Can't find unions anywhere for less than $45 for a 1". And the BSPT fittings are not widely available..
Question by: Elisabeth Duarte on Mar 5, 2017, 9:45 PM
Hey there,
If Neptune offers a fittings kit, we would most likely carry this, but currently I don't have any info indicating we would be carrying BSPT fittings or unions outside of this. That said, I'm happy to bring this up with our product team to evaluate whether this is something we should start bringing in!

Have a great day!
Answer by: Zack on Mar 9, 2017, 1:36 PM
What is the length of this unit with the unions installed?
Question by: John Flagg on Feb 23, 2017, 12:13 AM
Hey John,
The 1" flow monitor measures 4 1/4" and has a cord length of 16'. If you have any other questions, let us know!
Answer by: Jason Smith on Feb 23, 2017, 1:40 PM