# Wet vs dry dental suction systems

NHS England's HTM 02-01 (2026) classes dental vacuum systems as dry, semi-dry or wet: in dry systems an air separator removes liquids and debris before the air reaches a separate pump, while in wet systems air and liquid enter the pump to be separated; it says installations should be assessed individually.

In semi-dry systems, a similar separation takes place but the vacuum pump and the separator are combined in one device. In wet systems, a filter first removes the larger solids. HTM 02-01 does not describe the merits of each system, because installations should be assessed on an individual basis to find the most effective solution.

| HTM 02-01 (2026), Part A, chapter 11 | Dry system | Wet system |
|---|---|---|
| Separation | An air separator removes dental detritus, sputa and cooling water from the airflow and passes them to a drain before the air enters the pump; separator and pump are two different devices | A filter removes the larger solids; air and liquid then enter the vacuum pump, where they are separated |
| Vacuum line | Relatively dry and clean, which helps minimise bacterial contamination of the line; where the separator sits close to the pumps, much of the pipework still carries detritus | Liquid is also aspirated through the pipework (as in semi-dry systems) |
| Pipework layout | A series connection is often used, as only air is aspirated through the pumps | A star arrangement, with each chair draining back through its own pipe to the pump/separator unit, is quite common, because liquid in a series layout could cause a loss of performance at some chairs |
| Bacteria filter | May be feasible and is certainly desirable between the (condensate) separator and the pump inlets | Not practicable upstream; where upstream filtration is not possible, a bacteria filter should be fitted in the pump exhaust line |
| Plant conditions | Excessive condensation can occur where pipework is exposed to low temperatures; if necessary, a condensation separator with an automatic drain should be fitted | Keeping a minimum temperature of 10 °C is particularly important; freezing could cause considerable damage |

## Other points in HTM 02-01

- An amalgam separator should be included in all systems.
- Electrically driven side-channel pumps are frequently used in dental vacuum systems and may be combined with a separator unit; liquid ring pump systems typically include water-saving measures and may be fed from a reservoir or from the water mains via an air gap.
- Medical vacuum systems should not be used to extract bodily fluids during dental procedures.

See [what a dental central suction system is](https://library.ultracontrolo.com/answers/what-is-a-dental-central-suction-system/) for how HTM 02-01 sizes these plants.

## ULTRAVAC DENTAL

ULTRAVAC DENTAL is the Ultra Controlo centralised suction system for wet aspiration. It uses SCB side channel vacuum pumps with speed variation, a QuVAC controller that rotates the pumps and starts them progressively, and stainless steel vacuum stabilisation tanks. The datasheet table gives the number of chairs per model in two columns, 100% and 60%, from the V300 (1 chair) to the V18000 (60 chairs at 100%, 100 chairs at 60%).

### Can a dental suction system have a bacteria filter before the pump?

HTM 02-01 (2026) says it may be feasible and is certainly desirable in dry systems to fit one between the separator and the pump inlets; in wet systems this is not practicable.

### What minimum temperature does a wet dental vacuum plant need?

HTM 02-01 (2026) says maintaining a minimum temperature of 10 °C is particularly important for wet vacuum systems, because freezing could cause considerable damage.

## Sources

- [NHS England, HTM 02-01 Medical gas pipeline systems, Part A (2026 edition), paragraphs 10.14, 11.5, 11.6, 11.10, 11.11, 11.15, 11.16, 11.21 and 11.31 to 11.33](https://www.england.nhs.uk/wp-content/uploads/2016/05/health-technical-memorandum-02-01-medical-gas-pipeline-systems-part-a-design-installation-validation-verification-aug-2026.pdf)
- [ULTRAVAC DENTAL datasheet, pp. 2 and 3](https://www.ultracontrolo.com/products/ultravac-dental)

Reviewed: 2026-10-22. Ultra Controlo engineering. https://library.ultracontrolo.com/compare/wet-vs-dry-dental-suction/