The obvious is no water required in most dry vac systems. What is often overlooked is the need for exhaust and piping. With a wet system the air goes down the drain with the exhausted air and debris.

With dry vac you require a good air-water separator to allow the liquids to drop out of the air stream so they do not go through the pump. There are many different types that we can look at another time.

The exhaust piping is required to move the always hot, sometimes moist, mostly smelly air from the pump exhaust to outside the building. The only dry vac I know of that doesn’t have hot exhaust is the one using oil sealed rotary vane pumps. In this case they have very specific requirements for exhaust piping in order to collect all the waste oil from blowing out the pipe. It is important to note that the manufacturer of the oil system dry vacs asks that the exhaust pipe slopes uphill from the pump at a slow angle. This type of hook up should not be used on any other dry vac. Why? Condensation. We have talked about how dry vacs handle water. Condensation forms lots of water in the exhaust piping when the air cools down. This water has to go somewhere. In the sloping up from the pump exhaust pipe scenario that water will run back down into the pump. So if you are replacing an oil lubricated dry vac with any other type of dry vac you should not reuse the first sloped section of pipe.

Some of the dry suction turbine or regenerative type pumps have an exhaust cooler to try to keep the hot very exhaust air from causing issues. With this type of pump the exhaust flow is very high compared to the inlet flow (remember you can only suck air through the suction tools that’s all the air you get into the high flow pump. The high flow system has a vacuum relief valve that allows the pump to suck in full flow (high flow) when it can’t get the air from your operations. This full flow has to be exhausted. Lots of hot air brings the potential for lots of condensation.

Note: in short exhaust pipe systems, 25-40 ft, most of the hot moist air doesn’t condense. The problem is with long runs or piping that goes through cool areas like unheated garages.

If the installer slopes the exhaust piping away from the pump (understanding the first 8 feet may be straight up, vertical), condensation is not an issue. The BaseVac dry suction system includes a self draining P trap on the pump made of high temp plastic. This trap collects any potential pipe related condensation and drains it to a floor drain by way of a small flexible hose.

How you pipe exhaust is important. In a low flow BaseVac system with an exhaust piping system of over 150 feet we have experienced gallons of condensation in a single day.

Be careful when you hear “this pump runs so hot it will burn that moisture off”. What it really means is “don’t worry, this hot pump will absorb the moisture from dentistry in the hot dry air creating hot moist air and it will keep the pump dry exhausting the moisture with the waste air. Condensation will form somewhere as the air cools, just be aware.