If your vacuum pump has lost pumping speed or is slow to pump down, the usual causes are a system leak, a blocked or undersized inlet line, contaminated oil, worn vanes or seals, or simply a pump undersized for the chamber. Pumping speed and ultimate vacuum are different things – see what is pumping speed.
1. Leaks
A leak adds gas load the pump must fight, slowing pump-down and capping the vacuum. Leak-test the system (see why a pump won’t reach vacuum).
2. Restricted or undersized pipework
Long, narrow or kinked inlet lines and clogged filters throttle effective pumping speed. Use short, wide, smooth connections matched to the inlet, and check filters.
3. Contaminated oil or worn vanes
Old oil and worn vanes reduce sealing and speed. Change the oil; if that doesn’t restore performance, the pump likely needs a service.
4. Pump undersized for the job
If pump-down was always slow, the pump may simply be too small, or need a booster. We can size a suitable pump.
Pump down taking too long?
Tell us the chamber size and pump model and we’ll find the bottleneck – or size a faster pump. Email [email protected] or request a quote.
Frequently asked questions
Why is my vacuum pump slow to pump down?
Usually a leak, restricted or undersized inlet pipework, a clogged filter, contaminated oil or worn vanes – or the pump is simply too small for the chamber.
How do I increase vacuum pump pumping speed?
Fix any leaks, use short wide inlet pipework, replace clogged filters and change degraded oil. If the pump is undersized, fit a larger pump or add a Roots booster.
Is losing pumping speed the same as losing ultimate vacuum?
No. Pumping speed is how fast the pump removes gas; ultimate vacuum is the deepest pressure it reaches. A pump can lose one, the other, or both – the causes overlap but differ.
Written by the Girovac technical team. Girovac Ltd has supplied and serviced industrial and laboratory vacuum equipment from its North Walsham workshop since 1983. Last updated: July 2026.