Vacuum hose size vs efficiency.

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Old 12-18-03, 02:15 PM
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Vacuum hose size vs efficiency.

I have a small Shop Vac that has 1 1/4 hookup and a 6 foot hose! I will be getting a large Wet/Dry with a 2 1/2 inch hookup.
Neither of these Vac's have a long enough hose, I want at least 12 feet of flexible hose.
If I use 2 1/2" hose on the small Vac will it change it's suction properties very much, how about the added length on both vac's?

Changeling
 
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Old 12-18-03, 03:46 PM
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Vacuums depend upon static pressure or speed of moving air to do their assigned tasks. A larger hose will move the same amount of air with less velocity.

When I needed a longer hose for my small vac, I got a length of bilge pump hose from lowes and slipped it over the end of the small hose on the vac and had what I needed. I bought about 8 feet. An added benefit is that the white bilge hose won't rub off on things the way the black vac hose will. It seems to vacuum as well with the extra length.

Hope this helps.
 
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Old 12-19-03, 05:17 AM
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Changeling:

You would likely be ok with a 2 1/2" x 12' hose on the bigger vac but you would probably loose too much velocity on the small one.
 
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Old 12-19-03, 12:07 PM
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Is the static pressure and velocity directly related to horse power?
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Old 12-19-03, 12:42 PM
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I'll try.

changeling:

No, static pressure is directly related to the performance capability of the fan in conjunction with flow characteristics of the hose. The smaller the hose the higher the static the higher the the velocity but the smaller the volume.
You want a high volume and velocity but also in a larger hose to not plug up. If you put a large hose on a small machine the volume goes up but the velocity and static go down.
In other words a large hose on a small vac will cause debris to stall half way and plug the hose. A small hose on any vac will cause material to plug if too much debris is sucked up.
This is why bigger is better, big hose to allow stuff to pass and power from the vac to maintain velocity and volume.

The fan is what does the sucking and is directly responsible for the vac's hp requirements.
When looking for a vac, mfr's will state the vac's hp as a measure of it's capability.

The problem is the rating they use to determine hp is not one that is accepted as a true measure of it's continuous power capability.
What you need to do is find the actual cfm at x static rating.
For a mfr to give you the cfm without telling you at what static pressure their rating was taken at, would be a totally useless number.

Most better vac's will give this info, although usually at the back of the manual and in fine print.

If I get a chance I'll go out to my shop and dig out the book for my recently purchased wet/dry Craftsman shopvac to see what the specs are.
For what I paid for it and how well it works as an econo dust collector you may find something like that would suit you.
 

Last edited by GregH; 12-19-03 at 05:46 PM.
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Old 12-20-03, 11:31 AM
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Thanks Greg, awesome answer, I understand. I really appreciate the help. It would be nice to see the figures on your Craftsman for comparison.
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