This question is the last to be asked by someone thinking about switching from dental wet suction to a dry suction system. The answer should be “Relax, it will never happen, we have this safety and that switch all to protect your system”. But it does happen. Safety switches and floats can be switched off, unplugged or slow to respond letting water into a dry pump.
The result is normally not good. An oil lubricated pump (I like saying that, but how can it be dry, oil is wet!) will mix the liquid with the oil and the pump will fail due to lack of lubrication. Good news is it takes time to fail and if you catch it quickly and change the oil and everything will be OK. You will notice the pump cannot reach its ‘’Hg maximum because the oil water mixture no longer acts as a good seal inside the pump.
A turbine or regenerative blower vacuum pump is made of white metal and aluminum. Moisture will corrode the internal components eventually decreasing the required internal clearance causing pump failure. I have witnessed such pumps running full of water until the pump overloads and shuts off. The water often drains through the pump into the motor. This causes a motor failure when you try to restart the pump. If you catch the water in the pump and can take the pump apart and thoroughly drain and dry it, the pump may be OK.
The rotary carbon vane pumps come in two types, those with hydroscopic carbon vanes and the BaseVac design with non-hydroscopic carbon vanes. This is important because hydroscopic carbon vanes absorb water and swell in size. They then stick in the pump and do not slide in and out the way they should. This often results in broken vanes.
The BaseVac pump can actually work all day with water running through it. The vacuum level drops by 5’’Hg but it has 25’’ hg to start with. This has happened more than once. The trick is to do nothing until you have finished all dental suction for the day. At the end of the day, correct the water problem (usually caused by a closed drain valve at the water separator) and drain the pump. The front comes off the pump using an Allen key. Once the water is out you run the pump over night with all suction tools closed and the internal heat will dry the pump out. Ready to go again next morning. Not all dry vacs respond to water the same. BaseVac has the history of surviving and continues to work.