If the unit does reach the required mmhg level, then there is a problem with the accessories. Replace 1 item at a time and repeat points 2-4 above until you have located the part that is causing the problem. Replace the dysfunctional part/s.
If you find that suction is not reaching the above mmhg then something in the unit is causing a problem. It will need to be repaired professionally. See below.
** Please note that in-warranty DeVilbiss suction units may take up to 2 - 4 weeks to be returned to you due to ongoing delays relating to COVID-19. If this is likely to impact your business, we highly recommend having a backup unit if you do not already have one. **