Vacuum Testing - I want to compare different shop vacs and hoses

[Doug Hobkirk]

I connect several tools to my shop vac and I use a Thien design separator.

Saw table (Eureka Zone) tools (10" saw & router) have 1.5" fittings
Rigid sanding table = 2.25" (currently w/ 1.5" stepdown adaptor)
I also have other tools, but these are representative
I have at least two 2.25" hoses (not including the one to the separator) and two 1.5" hoses: 15' and 40' (a "pool" hose with rubber end fittings)
I also have a Porter Cable shop vac with 1.5" hose - it's suction is equal or better than the Craftsman
Separator is 30G metal can, plywood top I routed, Rockler fittings - it works well, I hear no leaks

I am re-configuring things. I have so many questions my brain is melting. So, experts and/or experienced people, please help me:

Does 2.25" hose intrinsically have better suction than 1.5"?
Does a longer hose intrinsically have better suction than a shorter hose (same size and construction)?
Is it significantly better to use a 2.25" hose to a 2.25" tool rather than a 1.5" hose into a stepdown adaptor at the tool?
Is there a better practical suction test than holding the end of the hose against a 1.5# plastic box?
Does suction automatically decrease for every additional volume of air space in the system? I.e., like the separator.
Is there a good test for leakage at the couplings?
Any general recommendations? Use the PC? Use 2 different hose systems after the separator (the fittings are easily accessible)? Forget about it and ride the bike for 2 hours?

Thanks, as always.

[Rod Sheridan]

I connect several tools to my shop vac and I use a Thien design separator.

Saw table (Eureka Zone) tools (10" saw & router) have 1.5" fittings
Rigid sanding table = 2.25" (currently w/ 1.5" stepdown adaptor)
I also have other tools, but these are representative
I have at least two 2.25" hoses (not including the one to the separator) and two 1.5" hoses: 15' and 40' (a "pool" hose with rubber end fittings)
I also have a Porter Cable shop vac with 1.5" hose - it's suction is equal or better than the Craftsman
Separator is 30G metal can, plywood top I routed, Rockler fittings - it works well, I hear no leaks

I am re-configuring things. I have so many questions my brain is melting. So, experts and/or experienced people, please help me:

Does 2.25" hose intrinsically have better suction than 1.5"?
Does a longer hose intrinsically have better suction than a shorter hose (same size and construction)?
Is it significantly better to use a 2.25" hose to a 2.25" tool rather than a 1.5" hose into a stepdown adaptor at the tool?
Is there a better practical suction test than holding the end of the hose against a 1.5# plastic box?
Does suction automatically decrease for every additional volume of air space in the system? I.e., like the separator.
Is there a good test for leakage at the couplings?
Any general recommendations? Use the PC? Use 2 different hose systems after the separator (the fittings are easily accessible)? Forget about it and ride the bike for 2 hours?

Thanks, as always.

Does 2.25" hose intrinsically have better suction than 1.5"?YES

Does a longer hose intrinsically have better suction than a shorter hose (same size and construction)?No, The opposite is true

Is it significantly better to use a 2.25" hose to a 2.25" tool rather than a 1.5" hose into a stepdown adaptor at the tool?YES

Is there a better practical suction test than holding the end of the hose against a 1.5# plastic box?Yes, you measure airflow and pressure for different pressures, the graph will allow you to compare it to other devices tested.

Does suction automatically decrease for every additional volume of air space in the system? I.e., like the separator.Suction isn't what you're worried about, it's airflow, and yes it decreases for every restriction such as smaller hoses, longer lengths etc.

Is there a good test for leakage at the couplings?

Any general recommendations? Use the PC? Use 2 different hose systems after the separator (the fittings are easily accessible)? Forget about it and ride the bike for 2 hours?

Regards, Rod.

[Art Mann]

I will just say that I agree with Rod on all counts.

[Mike Henderson]

I'll add to Rod's excellent comments: Most "name" shop vacs are good so pick the quietest. You're going to have to listen to it a lot. Some of them are real screamers.

Mike