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Stopping the Drip, Drip, Drip of the Highspeed

Updated: May 20, 2022

Having trouble with a leaking handpiece? Of course, "leak" can mean water coming out from somewhere it isn't supposed to (for example, the seams of the coupler) or coming out WHEN it's not supposed to (generally, this means it just doesn't shut off but it may also start on its own as soon as you lift the handpiece up).


Just as with the syringe, if you've got water coming out from someplace it isn't supposed to, you've probably got a worn gasket or O-rings. Screw-on couplers use gaskets, swivel quick disconnect handpieces use O-rings. Familiarize yourself with what you have and keep spares on hand. If you've got water coming out under the unit when you run your handpiece, you've probably got water in the air line, i.e. cross-over. See previous discussion on that.


If water is coming out of its own volition (or just won't stop) there are a number of possible causes, one of the simplest to check and rectify is incorrect supply pressure.


In order to function properly, most delivery systems require 80 psi of air at the source (junction box). NOTE: this is not the air pressure shown on the gauge on the unit, that is for your drive air. You'll need to look at the gauge in your junction box (frequently at the foot of the chair, but it can be located other places as well). The gauge should read 80. If the gauge shows proper pressure, have an assistant hold down the air button of your syringe for a prolonged period (about a minute should be enough) and see if the pressure remains steady (it may dip by a couple pounds, but should stay at or very near 80). If the pressure remains steady, your pressure is fine and you can skip down to the "water relay" a few paragraphs below). If the pressure shows good pressure at rest but dips down once in use, you have a clog. Check your filters and trace the lines. We covered clogs in a previous post as well. If the air pressure shows low from the outset, continue on for how to adjust it.


The photo below shows a junction box with a Beaverstate air master regulator valve in place. To adjust the pressure in this valve, there is a set screw at the end of the valve, so you need to use a hex wrench to adjust the pressure. With this particular valve, there is also a lock nut which needs to be loosened. Most regulators will have some sort of locking mechanism (lock nuts are common) to prevent the pressure from slipping once set.



With the lock nut loosened, you can then turn the set screw, in to increase the pressure and out to decrease it (yes, this is counter-intuitive). IMPORTANT NOTE: In order to adjust the pressure, you must have an "active flow", that means the air needs to be moving. The simplest way to accomplish this is to have an assistant hold down the air button on the air/water syringe while you are turning the adjustment screw. You can then watch the gauge until you have the pressure where it needs to be. Once you've achieved proper pressure, tighten the lock nut to secure the adjustment.


If connected to municipal water, you will have a similar valve and means of adjusting the water pressure. The water should not be set to more than 1/2 the pressure of the air. In most cases, 40 psi max. High water pressure can allow the water to simply blow through valves and continue to leak regardless of what "should" be happening. If your water pressure is too high, repeat the above steps with the water valve (while holding down the WATER button on the syringe) until the pressure is set where it needs to be. If you don't have a gauge on the water (common if using water bottles) you can "eyeball" the water pressure with the air/water syringe. For every 10 psi of water pressure, you should get approximately 1' of water stream out of the syringe. This means that if your water pressure is set correctly, your syringe should shoot about 3'-4'. As you'll be operating the syringe while making the adjustment, you can simply watch the stream as you adjust.


After your pressure has been adjusted, run everything for a minute or two so that line pressure can be exhausted and the new setting will take effect. After that, test for performance again.


If difficulty persists after adjusting your pressure (or, if your pressure is fine), it is then time to look at one of the most common causes of water leakage from the handpiece, the water relay valve. This is an air-activated valve that turns the water on to the handpieces when you step on the foot control.



The photo shows the inside of a Beaverstate brand delivery system. The water relay is marked. There are many other styles of water valve, but almost all of them have the same number of connections, three. They have water connecting into the valve, water coming out of it, and an air line connecting to activate it. Many of these valves are cubical or cylindrical (usually brass) but almost all will have three lines connected. Replacement valves are available from most dealers and there are many after-market compatible valves for most units as well.


If you have an A-dec unit manufactured after 1982 (about), you will not have a separate water relay valve. A-dec units have water on/off function built into the control block. If you have an A-dec unit of more recent vintage (the vast majority of them in service) and your pressure is ok, you'll likely need a block re-build kit. There are kits available for the various blocks used by A-dec over the years. They can be purchased through A-dec's dealer network but there are also many good after-market sources of repair kits as well.


We encourage subscribers to reach out to us with the details of their unit for further assistance.


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