Quote Originally Posted by Lonnie View Post
One aspect of this shop vacuum hose thread that seems to be important is suction and, hence, air flow. While trying not to get too technical about it, this suction amount is measured in inches of mercury or in/Hg. This measurement is derived by how far in inches the heavy liquid mercury can be moved up a tube when suction is applied to it. This is "different" than air flow, which is cubic feet per minute, or cfm and is how much air (cubic feet being volume) can be moved through a opening (orifice) in one minute of time. You have all seen pictures in vacuum cleaner advertisements of a particular make and model of vacuum cleaner being able to lift a bowling ball up. Suction is air flow, but in reverse, because it creates lift, hence the in/Hg measurement, with the Hg being kind of the weight part of it with how far a suction can lift it up the tube. There are four things that have an effect on creating this suction in a shop vac:
1) The power (horsepower) and speed (revolutions per minute) of the electric motor
2) The impeller mechanical design and housing that produces the actual suction
3) The filter media, which will limit the canister air movement and cause air resistance
4) The hose media and nozzle attachments, which also causes air resistance

There is a reason Dyson spent millions of dollars on design and trial-and-error development of item two: the unique and patented super-efficient lightweight impeller and housing design for a consumer vacuum.

The Metro has a more powerful and "robust" motor design, item 1, than most shop vacs, and its metal construction verses molded plastic canister and housing of typical shop vacs, but it is also the reason it is more expensive. You do get what you pay for, sometimes.

My long-winded point is that filter media is overlooked and keeping that clean to provide less resistance is sometimes forgotten, or the media type itself. I have Sears Craftsmen Shop Vac that can be fitted with thee different filter medias:
1) Standard paper (AKA, Original Equipment of Manufacturer that came with it
2) Upgraded paper for fine debris, like fireplace ash
3) HEPA-grade media for ultra-fine debris, like sheet rock particle board dust

With each "upgrade" in a filter media, the more resistance in air flow it creates, and hence its reduction in suction. I "learned" this from a HVAC service tech, who informed me my allergen-rated furnace filter will greatly reduce my furnace fan motor life due to its higher air-restriction because of the finer media needed for its allergen rating.

I use the"upgraded paper" filter on my Shop Vac because I deal with dried clay debris or home construction debris in the carpets of vehicles I clean, so it is not sucked through the filter and exhausted into the air in my garage when vacuuming. Its a small trade-off I am willing to live with. With that, though, I do try to keep my filter clean as possible. I clean it after every dirty job, if possible, even just knocking out the trapped dirt in the filter. The other thing I do is to wash (scrub and clean) the inside of the nozzle attachments periodically and the hose as well. If you use your shop vac as a carpet extractor OR vacuum when your carpets are damp, you probably have solidified mud in both the nozzle attachments and hose. While it may offer a minimal amount of air movement resistance, keeping your filter media clean and the hose and nozzle attachments clean can help contribute to optimal shop vac suction performance. (Which only proves that you REALLY are an Obsessive-Compulsive Detailer, Captain Obvious!)

Edit: I forgot to post this tip about keeping a filter clean when vacuuming a REALLY dirty environment, like dried clay silt after a flood or a lot of fine/short animal (darn cats and dogs!) hair, is to wrap paper toweling (like Bounty, but not the hard, brown or white hand toweling) around the filter, just enough to encircle the filter once and tape it on with masking or duct tape along the edges seam and then to the filter at the top and bottom. Yes, it restricts the air flow a lot, BUT it makes for easy clean-up of the filter. You may even find it necessary to put an new piece of toweling on should you do a lot of vacuuming. Just a hint that might save your from having to discard/throw-away a shop vac filter after such usage.
I appreciate the write up, Thanks.

Have you tried the Gore, Hepa filter from Shop Vac? The filter supposed to have a non stick surface, while maintaining its suction power. Clean up is supposed to be just a tap and everything should fall out of it.