Repairing yourBestway, Coleman or Lay-Z-Spa water flow sensor.

What is the water flow sensor.

water flow sensorThe water flow sensor is just as it's name says, it is use to tell a system that water is flowing. Seen to the right is the water flow sensor used in many of the Bestway, Coleman and Lay-Z-Spa branded inflatable hot tub models. These sensors are one way flow sensors meaning that they will only sense water flowing in one direction. Failure of this sensor is one of the causes of the dreaded E01 or E02 errors seen on the pump/heater unit of many of the listed brands of inflatable hot tubs.

How does the flow sensor work?

The operation of the water flow sensor is very simple. reed switchThere are three main components to the sensor. The first part is the main sensor housing. The housing has water inlet and outlet ports for the water to flow through. The second part is the magnetic reed switch, or proximity switch. This part is the small black tubular piece with the two wires coming off of it like the one seen to the right. When this piece senses a magnetic field, a small switch inside makes contact completing the circuit in the two wires. original sensor flapThe third part of the sensor, quite obviously, is the magnet. The magnet is housed in a small plastic paddle like the one seen to the left. When water is pushed through the sensor housing, this magnetic paddle will get pushed up near the proximity switch triggering it telling the system that water is in fact moving. This sensor is a one way sensor meaning that it will only sense the flow of water in one direction. Because of this, care must be taken to install this sensor in the correct direction for proper operation.

The main problem with these sensors.

The biggest problem with these sensors is that the magnetic paddles in them fail. The reason for this is because magnets can easily start to rust if exposed to water. rusty sensor flapWhy do magnets rust? Magnets work because they are made of ferrous metals which contain iron. Magnets need iron to attract, and iron rusts when exposed to oxygen and water. Rust reduces the attraction of a magnet. This is why the sensors fail when the magnet gets rusty. The original sensor paddles have the magnet inset into a hole in the center and then a dab of epoxy glue is put on top. Over time, the dab of epoxy can come loose from the paddle exposing the magnet to the water eventually causing it to rust and fail. The plastic around the magnet will start to crack because of the magnet swelling which allows more water in causing it to snowball into failure.

Inspecting your sensor.

pump/heater unitHow do you find out if your sensor has failed or is starting to fail. The first thing is to unplug your pump from the mains socket. Never work water stopperon your unit with the power plugged in. Now place your black rubber water stopper caps, seen on the left, over the water ports inside your tub. This is to prevent water flowing out of the flow sensor when you take the cap off. Next, remove the cover from your pump/heater unit by removing the six screws in the middle of the unit as indicated in the picture to the right. Once those screws are removed, carefully lift the top off being careful of the ribbon cable. inside pump/heaterNow, separate the black connectors on the ribbon cable slightly down from the control panel inside and set the cover to the side. In the picture to the left, the arrow points to the water flow sensor. Start by disconnecting the small plug on the two wires attached to the top of the sensor. Now remove the four screws from the top of the sensor and set them aside. cover with flapCarefully lift the top of the sensor off being careful not to loose the round o-ring seal under the cap. Inspect the plastic paddle under the cap looking for signs of cracks in the plastic, and signs of rust like the one shown to the right. If you see any of these things or other damage to the paddle, it is best to replace it. While you have the top off, you should also inspect the o-ring for any signs of wear. If there is even the slightest bit of wear on the o-ring, it is best to just replace it. Some would have you replace the entire water flow sensor assembly which can cost you between $50 and $75 US dollars just for the part. On top of that you would have to dismantle the unit even further to be able to remove the old one and install the new one. Why replace the whole sensor when you can just repair it.

Testing the sensor

To test the water flow sensor you will need a multimeter set to the continuity setting that will indicate an open or short condition. If your multimeter does not have a continuity setting you can put it on a resistance setting to show either infinite resistance or zero ohms (or near zero). You will also need two small pieces of stiff wire like in the picture to the right. The wires will be used to connect to the sensor to do the tests. Start by wrapping the small wires around the tip of the test probes and inserting them in the two holes in the connector. You will feel a bit of resistance when pushing the wires in, but they should be inserted enough to make a good connection with the connectors inside. Once connected, the water flow sensor should show an open or infinite resistance when the paddle is hanging down and a short or zero ohms when the paddle is in the upward position resting on the cover plate. If you don't read a shorted condition when the paddle is in the up position, you most likely have a problem with the paddle magnet. The sensor that senses the magnetic paddle is the black tube looking part that the wires connect to. It is extremely rare that that part will fail. If you have another small neodimium rare earth magnet (refrigerator magnets may not be strong enough) you can place it near where the paddle will hit the cover and see if the sensor triggers. If it does, then your paddle needs to be replaced. I sell both the replacement paddles as well as kits that include the paddle and the o-ring seal for the top of the sensor housing. Both the paddle and the kit version come with a replacement nylon pin to attach the paddle as many times these get broken. You can get both at my web store by clicking here. On the extremely rare chance that the sensor ( black tube) is bad, you may need to contact Bestway or purcase a new water flow sensor, but as mentioned, it is extremely rare that this part goes bad.

Repairing the sensor.

To repair the flow sensor you should by now know what parts you will need for the repair from the inspection you just did above. Whether you nee just the paddle, or the paddle and o-ring, we have you covered. If all you need is the water flow sensor paddle, this can be purchased from our store as a kit that now includes the retaining pin for $12.49 plus shipping by clicking here. If you also need the o-ring, we sell a kt that contains the paddle, retaining pin and the o-ring. These kits can be purchased from our store for $13.49 plus shipping by clicking here. If you decide that you want to go to someon else to purchase the paddle, there are some things that you need to watch out for. Be weary of the ones like the one on the right. In this style, the magnet is mounted directly on the top, completely exposed to the water. Because of this, the magnet will start to rust and fail significantly quicker than the ones that I sell in which the magnet is completely sealed in plasic. The other thing with paddles like this one is that people make these out of PLA plastic. This type of plastic has a lower melting point and if exposed to too much heat, it will start to deform. Once the plastic deforms, the magnet can pop out of it's hole causing another failure. Our paddles, seen on the left, are made completely from ABS plastic which is more flexible and has a lot higher melting point making it less prone to deforming and failure. Also the magnets on our sensors are completely encapsulated in plastic with little to no chance of the magnet touching water and rusting. Buy our parts with confidence.

Now on to replacing the sensor paddle. These sensors use a small nylon retaining pin to secure the paddle to the sensor cap. This can easily be removed by pushing on the back side of the pin, the side with the slot in it, with something flat. The pin should come out pretty easy. Simply pull the pin out enough to allow you to get the old paddle off. Put the new paddle in place and push the pin back through the hole. Our kits now include the retaining pin. It's that simple. Once you have that done, if needed, remove the old o-ring and drop the new one in it's place. Be sure to inspect and clean the channel that the o-ring sits in prior to installing the new one.


So that's it, you just repaired your water flow sensor for under $16 US dollars rather than spending $50 plus and all the extra time and effort

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15 Replies to “Repairing yourBestway, Coleman or Lay-Z-Spa water flow sensor.”

  1. Wow, glad Ive just found your site. I love my Colemen, but have problems as well. One “egg” suddenly stopped heating. I wont go into what I know and dont know right now , but this is my 3rd tub so I do have many parts. Just need to learn more. Rex

  2. Dan can the magnetic reed switch be tested ? Did a continuity, with no results, did put a magnet on the end and still no continuity… I have been looking for this part online with no success, so if you know where it could be purchased, I’d appreciate the info. ….. thanks for your Knowledge….. Ron

    1. It’s very rare that these fail, but not impossible. Are you sure you had good contact with the connector when you tested?

  3. Thanks for the info! I was having an intermittent E02 code. I suspected flow sensor issue, and when I got it apart, the plastic pin was barely hanging in there (very worn and not a tight fit). My guess is that the flap has been getting stuck because of it. any suggestions on what to replace the pin with? small machine screw and nut could work, but rust is not my friend here.

    I did try to cheat it and force the flow sensor to stay closed, but that set and E01 code as soon as turning it on, lol. Couldn’t trick the computer.

    1. Trevor, I have been trying to find a place to get replacement nylon pins from, but have been less than successful. I sell replacement magnetic flaps and would like to include a replacement pin with my kits, but I have to find a place to get them first. I have seen pics though of people using what looks to be an aluminum pin. Another option would be a small screw with a nylock nut, but if you go that route, you would have to go stainless, because as you pointed out, rust is not your friend in that situation.

      1. Thanks Dan! I will probably go with a small stainless screw and a nylock nut. Should at least last for awhile.

        1. Trevor, I just found a supplier for the nylon pins. I just received my samples from the manufacturer and they look perfect. I ordered a large quantity and soon I will have these available in my web store. I will include them in my kits with the replacement paddle.

    2. I did the same, and also got the E01 code. It’s
      because on start up, the unit needs to know there is no water flowing (circuit open). If the sensor is taped together, the system will always think that water is flowing (circuit closed), even on start up.
      (1): I removed the sensor flap from inside, and used electrical tape to hold the sensor flap and sensor together externally. (2): Then, I ran the sensor wire and clip through a small hole in the outside of the unit, leaving it outside the unit once reassembled. (Make sure the connector clip is on the outside of the unit when the case is all screwed back together. You will need to disconnect and reconnect in an upcoming step). (3): Disconnect the sensor at the clip. (4): plug in the unit. (5): power on the unit, and press the pump button to start the water flow. (6): As soon as the water starts flowing (within 1-3 seconds) plug the sensor back into the clip.
      This sequence allows the system to start with an open circuit, the remain running by tricking it into thinking water is flowing.
      This 100% worked for me, and is a way of hacking the pump.

  4. I was receiving the E02 error and reached the point where i had to open the egg. i inspected and, cleaned out the flow sensor and replaced the impellar. The pump works now. 2 problems:

    1. Did i re- install the flow sensor leaf/paddle in the correct direction? I have the leaf positioned closer to heater to it would flip toward the tub. Is this correct?

    2. I am getting leaking at each hose i unconnected. The old O-rings appear normal and i cinched the straps down well, still leaking. I am also getting leaking at the impeller box. Suggestions appreciated.



  5. Dear Dan and everyone else who posted here,

    Thank you for the invaluable information!
    I was fighting a random E002 for months and would never have been able to fix it without your help.

    My problem was that the nylon pin that holds the flow sensor magnet had eroded over a period of two years.
    It still held the magnet in place but instead of allowing the magnet to go up and down with water flow the magnet was more or less flopping around never making proper contact with the black reed switch above.
    Sometimes it would work for days, sometimes it was only a few minutes before the E002 appeared.
    To diagnose the problem I connected an ohm meter across the black sensor lead plug and a garden hose on the inlet (no need to power up the unit – just turn on the garden hose and watch the ohm meter reading)
    I recommend using a cheap $10 analog meter with a needle display as opposed to a digital display meter.
    With the water running through the unit I could clearly observe the meter needle bouncing as opposed to be solid to one side.

    The fix was to remove the nylon pin and replace it.
    I found a 3/16 aluminum (!) rivet and cut off the shank.
    Cut to the right length the new pin is held in place by contacting each side of the sensor housing and the magnet is held in place.
    Now the magnet can move as it is meant to during water flow and the ohm meter reading indicates solid contact.
    This fixed my problem after so much grieve!

    Hope this helps someone else!


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