Practice Tips #13: How to Repair a Leaky Syringe (Part 2)

In our last Practice Tips newsletter, Syringe Repair – Part 1, we discussed identifying and replacing your syringe buttons and other helpful tips. (Please visit our Practice Tips newsletter archive if you missed part 1 or if you would like to view any of our previous newsletters). This time, we show you how to correct leakage around the various orifices of the syringe.

Depending on the location of the leak, you will need to replace different o-rings. Getting to the o-rings in the “head” of your syringe is quite simple. All you need is a 5/32" allen wrench.

For most syringes, simply remove the syringe tip from the tip holding assembly. Put the wrench into the hexagonal hole, turn counter-clockwise, and the entire tip holding assembly will unscrew.

There are three different sized o-rings on most tip holding assemblies (for actual-size o-ring size identification print off our O-rings & Fittings Print Out:

  1. You will find one or two o-rings that fit inside the "tip nut" to hold the syringe tips in place (our o-ring #01-04). The tip nut is the chrome conical piece on the front of the syringe into which you place your tip. This is normally threaded onto the adaptor nut (brass piece with male threads that screws into the head of the syringe). For the “quick release” syringes, there will be two of these o-rings. For older style syringes, that have a nut that must be loosened to change tips, there will only be one. These o-rings are not used on “collar” style syringes.
  2. A skinny o-ring fits around the adaptor nut to help seal it to the syringe “head” (our o-ring #01-05). Replace this o-ring if you have leakage around the holding assembly.
  3. A small o-ring fits on the back of the adaptor nut (our o-ring #01-06); this o-ring keeps the air and water from mixing. HINT: Do you ever get that annoying blast of water when you press your air button? Replace this o-ring and that should fix the problem!

For the “collar” style syringes (push collar “ring” in to insert/remove syringe tip) you will use the same 5/32” allen wrench to remove the collar assembly. There are two visible o-rings for this style of assembly. To gain access to them, insert the wrench into hole where tip goes and turn counter-clockwise to remove the collar assembly. There is a spring behind the assembly, be careful not to lose it.

  1. Our #01-05 o-ring goes around the threaded portion of the collar assembly.
  2. Our #01-06 o-ring actually sits inside the head of the syringe where the collar assembly screws. You will see a small hole in the center of the syringe into which this o-ring will seat.


Both size o-rings serve the same purpose as with the tip nut assembly. Note: there are no tip o-rings (our #01-04) in the collar assembly- as the assembly holds onto the syringe tip with ball bearings.

Once you have replaced your o-rings, reassemble your syringe. Note: there is a notch in the collar on some collar syringes. Make certain that this notch is lined up with the pin at the bottom of the hole into which the collar assembly will screw into. Depress the collar fully before tightening to make certain it is properly aligned. If the notch is not aligned with the pin, you will be unable to depress the collar.

Once assembly is complete, turn the unit back on and test for proper function.

Congratulations! You are ready to go!


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