Practice Tips #18: Fixing Waterline Clogs

A lack of water flow in your dental unit causes concern, but fixing a waterline clog doesn't have to be stressful. Something we encounter every day are complaints of no water or very low water flow from various items in the dental unit. Lack of water flow from any part of the dental unit is almost always due to a clog. Clogs will happen.

No matter how many filters you have or what type of treatment system you use, debris gets into the waterlines. When dealing with the water that travels through a dental unit, this is a reality. How do you determine if it is a clog and not something else? No flow at all could be a clog or a failed valve. If you get good initial flow, but it rapidly falls of to nothing (or almost nothing), this is classic clog behavior.

Troubleshooting a Clog

Isolating the problem is a good rule for troubleshooting a delivery unit or any piece of dental equipment. If you systematically rule out the “working” items, you will end up isolating the problem so that you can take the appropriate corrective action. Let’s say you are getting insufficient water at the air/water syringe, try following these steps:

1. Check the syringe tip.

Is there an obstruction in the tip itself? Remove the tip and check the water flow. If everything is ok, try another tip or clean the clogged tip. Are you using disposables or barriers? Make sure a piece of the disposable tip did not break off in the syringe or a portion of the plastic from the barriers did not block the syringe hole. If you or your staff push the tips through the plastic barrier, you are almost certainly pushing a little piece of plastic into the syringe which will clog it up. If using disposable tips -- do your disposable tips need an adaptor? Check with the manufacturer of your disposable tips. Generally, if the disposable tip does not have a smaller skinny internal line, (just like a regular metal tip), it will require a specialized adaptor. Simply using the correct adaptor may correct the problem.

2. Check your syringe buttons.

Do they need replacing? For more information on syringe troubleshooting, see our Syringe Repair Practice Tips Part 1 & Part 2.

3. Remove the syringe from the tubing to check for flow.

Clamp off the tubing using a hemostat and remove the syringe from the tubing. Remove hemostat and check for water flow. If no flow, it is possible there is a clog in the tubing itself, try using some pressurized air to remove the clog or install new syringe tubing as biofilm may have built up in the line.

4. Check if there is flow where the syringe tubing attaches inside the unit.

Continue to trace the water backwards to the next juncture and so on until you find where the problem lies. You will use the same sort of isolation technique with other items.

Obviously, you will want to make sure you have water to the rest of the unit. If you have made sure that the compressor is on and that water is available to your unit from either a public water source or bottle unit, check to see whether you are getting water to the handpieces. Now that we’ve learned the basic technique of tracing the lines, here’s how to perform the same checks if you have no water to one of the handpieces:

  1. Check to make sure you have the water switch on, it is on either your unit or the foot control. Then, search for blockages as we did with the syringe above, noting that there could be a clog in the coolant waterline of the handpiece itself, (use a handpiece cleaning wire to remove any debris). Make sure to check the coupler.
  2. If that seems fine, you will have to move to the handpiece control block. Follow the handpiece tubing back to control block and remove the small coolant waterline tubing from the barb on the control block Check for flow, if you have flow, it is a clog in the tubing.

Insufficient Flow to Handpieces

If you are not getting sufficient flow to any of the handpieces:

1. Check your water relay valve.

There are normally three lines attached to this valve. One for air signal and an “in” and “out” port for water. Remove the outgoing line on the water relay valve and push your foot control.

  • If you have no water comes out, remove the airline from this valve and check for air signal. Detach the air line from this valve and step on your foot control. Air should come out of the hose.
  • If you have air, next verify that water flows into the valve. Disconnect the third line from the valve (water inlet) and see if you have water here.
  • If you have air and water going into the valve but not coming out, replace the valve.
  • If you have no air or water into the valve, continue to move backwards until you find where the air or water stops.

NOTE: Your handpiece water is air-activated, so you must have air to get water. So a clog in the airline could stop your waterline from flowing out of your handpiece too and need fixing.

2. Check your water filter (at the public water source).

Shut off the water at the manual shut-off, unscrew the filter cover, and remove the filter from the regulator/master valve. Leave the filter out, reassemble the valve, and check for flow. If the flow is fine, replace the filter. Some set-ups incorporate a separate filter from the master valve or regulator, but removing and fixing the filter should reveal whether or not the waterline clog occurred because of the filter. Fixing Waterline Clogs by Checking the Valve (#05-558)

3. Check the air and water pressures going to the unit.

Your water pressure could be set too low. Most delivery units operate best with a split of 80 PSI for air and 40 PSI for water. Please look at our Pneumatics Practice Tips for more information.

Fixing your waterline clogs helps run your practice with very little effort and cost. Regular dental unit maintenance and controlling the water quality with filters or self-contained water system keep things flowing.


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