Waterpik WP-450 Battery Replacement Guide

This guide will take you through how to open the Waterpik WP-450 cordless water flosser and repair it by replacing the internal rechargeable battery.

Waterpik WP-450 battery replacement guide

The disassembly and repair tutorial is based on the Waterpik WP-450 flosser model shown above but is also applicable to other cordless Waterpik models such as the WP-440, WP-450E, WP-455, WP-460, WP-462, WP-463, WP-464, WP-465 plus the WP-466. The WP-360 Waterpik models were made with two different types of battery pack, so you might be able to repair your WP-360 if it is the later version fitted with the same side-by-side type of battery pack shown here. The model number of your Waterpik flosser is marked on a label on the bottom of the flosser or on the back of the Waterpik behind the water reservoir.

Waterpik WP-450 flosser model number

The basic method is:

  • Open and dismantle your Waterpik flosser
  • De-solder the old rechargeable battery
  • Solder in the replacement battery
  • Reassemble the Waterpik and recharge the new battery

This is documented in detail below along with lots of pictures.

Disclaimer

Any damage to yourself, your device or anything else is entirely your responsibility. This guide is for professional, educational purposes only and is offered without guarantee or liability.

Video

We have created a short video from this guide to Waterpik WP-450 water flosser battery replacement on our YouTube channel, which you can also watch below.

Tools / Parts / Equipment

  • Waterpik WP-450 water flosser
  • Compatible charger
  • Soldering iron: Electronics grade (about 18-25 watt)
  • Solder: Lead-free silver solder is great for this
  • Solder sucker (also known as a desoldering pump) and/or desoldering braid
  • Small cross-head screwdriver e.g. Phillips no. 1
  • Large flat-bladed screwdriver: 5 to 8mm wide
  • Temporary tape
  • Scrap of cardboard
  • Optional double-sided tape
  • Replacement 2.4V Ni-MH battery with solder tags. Available through Ionic Industries here

How-To

To start with, empty the water reservoir of your water flosser. Then release the clip underneath and slide the reservoir downwards and off the bottom of your Waterpik. Also remove the nozzle/jet/tip from the top.
(Click on any picture to enlarge it.)

Waterpik WP-450 battery reservoir removal

Temporarily tape a piece of cardboard to the top of the Waterpik to protect it from getting scratched.

waterpik-wp-450-flosser-remove-nozzle-holder-1

Using a large, flat-bladed screwdriver resting on the cardboard gently pry the nozzle holder out of the body of the Waterpik. Make sure it doesn’t fly off across the room!

waterpik-wp-450-flosser-remove-nozzle-holder-2 waterpik-wp-450-flosser-remove-nozzle-holder-3 waterpik-wp-450-flosser-remove-nozzle-holder-4 waterpik-wp-450-flosser-remove-nozzle-tip-holder-5

The removed piece:

waterpik-wp-450-flosser-tip-nozzle-holder

Using a small cross-head (phillips) screwdriver remove the 4 screws from the back of the flosser arrowed below.

waterpik-wp-450-how-to-open-screws

Lift up and unhook the back cover to remove it.

waterpik-wp-450-how-to-open-remove-back

Remove the 2 screws holding the inner plate.

how-to-open-waterpik-wp-450-screws-x2

Start to pry up the inner plate that carries the pipework.

waterpik-wp-450-pry-open-inner-plate

Turn over the Waterpik and check that the charging socket is coming away with the inner plate and isn’t stuck to the front of the flosser.

waterpik-wp-450-charging-socket

Continue to lift the inner plate and move it slightly to the right.

waterpik-wp-450-remove-inner-plate

Gently pull the inner plate away from the top of the flosser while twisting it slightly anti-clockwise to disengage the nozzle release mechanism from the blue nozzle release button (arrowed below).

waterpik-wp-450-nozzle-release-switch

Continue to twist and remove the inner plate until it is free from the body of the Waterpik. Don’t lose the blue nozzle release button!

waterpik-wp-450-twist-remove-pump-plate waterpik-wp-450-flosser-dismantle

Turn over the inner plate to see the motor and battery.

waterpik-wp-450-motor-battery-removal

Note how this battery is right at the bottom of its compartment with a gap at the top. You will need to re-fit your new battery in a similar location to your original battery to ensure that the wires can reach the solder tags on the new battery.

waterpik-wp-450-battery-in-compartment

Note how the wires pass through cutouts in the battery retaining clamp.

waterpik-wp-450-flosser-battery-charging-wires

Remove the battery retaining clamp and note the polarity of the battery and its wires. The red wire goes to the positive battery terminal.

waterpik-wp-450-flosser-remove-battery-clamp

Time to get your soldering iron warmed up now! Using the soldering iron and a desoldering pump or some desoldering braid first desolder the black motor wire from the negative battery terminal. You might need to cut the wire where it is soldered to the battery tag if you have one continuous wire from the motor to the battery to the charging socket.

waterpik-wp-450-desolder-negative-wire-1

Desolder the wire from the charging socket where it is soldered to the negative battery tag.

waterpik-wp-450-desolder-negative-wire-2

Desolder the two wires from the positive battery tag. The black ‘wire’ in this photo is actually a sleeved electronic component – probably a diode to prevent damage in case the charger is somehow connected with reverse polarity.

waterpik-wp-450-desolder-positive-battery-wires

Pry the original battery out of its compartment. This one was held in with some weak glue.

waterpik-wp-450-cordless-original-battery-removal

Compare the original battery to its replacement, available from our shop here. Your original battery will be 2.4V and will probably have a capacity of between 1300mAh and 1500mAh. This can be safely upgraded to our 1800mAh 2.4V pack to give a longer running time between recharges.

waterpik-wp-450-flosser-old-new-battery

Note the relative positions of the positive battery terminals arrowed below. They are in opposite locations. On the left side of the original battery pack and on the right side of the new replacement battery pack.

waterpik-wp-450-flosser-new-battery-positives

We can easily reverse the polarity of the new battery pack by folding the solder tags back on themselves. First, fold the tags outwards.

waterpik-wp-450-flosser-new-battery-tags-out

Turn the battery pack over.

waterpik-wp-450-flosser-new-battery-pack-turn

Fold the tags upright, then slightly towards the back of the pack.

waterpik-wp-450-flosser-new-battery-pack-tags-upright waterpik-wp-450-flosser-new-battery-pack-tags-back

Trim the solder tags to a similar length as the tags on the original battery pack. You can leave them slightly longer for a bit of flexibility in fitting if required.

waterpik-wp-450-flosser-new-battery-pack-tags waterpik-wp-450-flosser-new-battery-pack-tags-trimmed

Test the fitment of the new battery and that the wires reach the solder tags. Once you’re happy with its position you can use a little double-sided tape to hold it in place. This is not essential as the retaining clamp will hold it in place later.

waterpik-wp-450-install-new-battery

Tin the two solder tags with solder, making sure that you do not melt the plastic sleeving of the battery cells as this could cause a short circuit.

waterpik-wp-450-tin-new-battery-tags

Solder the 4 wires to the new battery’s solder tags.

waterpik-wp-450-flosser-new-battery-soldered

Re-fit the battery retaining clamp, making sure that the wires pass through the slots in the clamp.

waterpik-wp-450-re-fit-battery-clamp

Re-fit the nozzle release button in the flosser’s casing and temporarily tape it into place so it doesn’t fall out.

waterpik-wp-450-tip-nozzle-jet-release waterpik-wp-450-nozzle-jet-release-tape

Check that the power switch is still off and that the speed selector switch is still in the position that matches the lever on the inner panel (both down in the photos below).

waterpik-wp-450-power-switch-speed

Hook the inner plate into the Waterpik’s casing at an angle so it goes behind the screw towers. First on the left side:

waterpik-wp-450-flosser-insert-motor-plate-0

Then on the right side:

waterpik-wp-450-flosser-insert-motor-plate-1

Manoeuvre the inner plate it so that the blue nozzle release button connects with the release mechanism correctly (arrowed).

waterpik-wp-450-flosser-insert-pump-plate-2

Remove the tape from the nozzle release button and check that it can be pressed in and springs out.

waterpik-wp-450-tip-nozzle-jet-release

The inner plate can be pushed fully into place.

waterpik-wp-450-flosser-motor-battery-repair

Check that the speed selector switch has engaged and moves the internal lever correctly.

waterpik-wp-450-flosser-speed-1 waterpik-wp-450-flosser-speed-selector-switch-2

While holding the inner plate into the casing by hand you can now lift up the whole Waterpik assembly and check that the power switch works by switching it on for a second or two. There should be enough charge in the new battery to run the motor a little.

Check that the charging socket is flush with the front of the flosser housing.

waterpik-wp-450-flosser-charging-plug-socket

Re-fit the 2 screws that hold the inner plate in place. These are self-tapping screws so to avoid cross-threading them drop each one into its hole then, before tightening each one, first give it half a turn or so anti-clockwise until they ‘click’ and drop into their thread.

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Re-fit the 4 screws that hold the back cover in place.

waterpik-wp-450-how-to-open-screws

Clip the nozzle holder back into place.

waterpik-wp-450-tip-nozzle-jet-holder-insert-1 waterpik-wp-450-tip-nozzle-jet-holder-insert-2

Check that the motor still runs then plug your Waterpik flosser in to charge for a full 24 hours.

Waterpik WP-450 battery replacement guide

You now have a fully repaired Waterpik water flosser! We’d love to hear about your Waterpik repair experience so please leave any questions, hints or tips in the comments section below.

Notes on Charging

The original charger supplied with the Waterpik flosser shown above is rated with an output current of 100mA. To fully charge the higher capacity 1800mAh battery from empty this will take 18 hours, plus the recommended additional 50% to compensate for losses (an extra 9 hours). This takes it up to 27 hours of charging for a full slow charge using the original Waterpik charger. Check your own charger to see if it is rated at a different output current.

12 thoughts on “Waterpik WP-450 Battery Replacement Guide

  1. Dear Friends

    I am 81 years old and I am unable to replace myself the batter of my waterpick model WP-462W / WP-462C.
    I live in Miami, Florida, USA
    Could I send my waterpick somewhare in Miami, or anywhare else, to replace the battery?

    Thanks so much for your help

    1. Dear Eladio,
      I believe your local TV repair shop or small appliance repair shop will be able to help you, especially if you can show them our repair guide. They will probably ask you to order the battery and then carry out the repair for you once the battery arrives.
      Hope that helps!

  2. Waterpik 450 replacement battery. Purchased the replacement battery and followed the instructions on your website video.

    Unfortunately it leaves out a vital step, the two screws holding the assembly into position under the main cover.

    1. Thanks for letting us know Stephen, we’ve now added the additional step to the guide.

      1. Yes the guide is ok but not the video!

        1. As a stop-gap an information flag has been added to the existing video about 55 seconds in. It will need to be re-edited from the source material and uploaded again.

  3. Hello, im looking for battery replacement for Waterpik Wp-450. What is the battery markings? The link on your site brings me to site in England. Anything in US? Thank you

    1. The link on our shop page should redirect you to eBay USA if you are physically in the USA when clicking on it. Alternatively, you can use this link to take you to Waterpik batteries on ebay.com

  4. In my unit the motor doesn’t work. Where I can get a replacement?

    Thanks

    1. The motor is probably rated at 2.4V – 3V. See the photo below for the markings on the Waterpik WP-450 motor used in the guide. It looks like the part numbers are FC-280SA-3540 and BD435505 although the latter might be a batch/serial number. It’s a common size of motor by Mabuchi but the main issue will be how the motor’s output shaft connects to the mechanism it’s driving. The output bush/cam/cog might be pressed on to the motor’s metal shaft and you will need to use a puller to remove it from the old motor and press it onto the new one. Does a drop of light oil on each motor bearing allow it to run?

      Waterpik motor WP-450

  5. Ionic admin.
    Was you able to pull out the metal gear , and pressed it onto the new one?

    thanks in advance!

    1. We haven’t tried this as we don’t have a puller.

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