Shop Vac hose question?

[imported_Lawdog]

This is for the Autopians who studied hydralics, or stayed at a Holiday Inn and know the answer. I have a 12 gallon 5 hp shop vac which is in like new condition ie has great suction. I want to lengthen the hose so I don't have to have it so close to the vehicle. I think it would be easier to use the smaller diameter 1 1/4" I think, than it would the 2+inch hose that came on it. So I was going to put a reducer on the hose and run an extra length of smaller hose. Question is, will going out the vac with the standard hose and reducing it to a smaller diameter hose increase or decrease the suction? Inquiring minds want to know

 

[LouisanaJeeper]

well, the easiest way to explain it is this way



you will be moving the same VOLUME of air. with the smaller tube the air will be moving faster in a smaller area, in the larger tube the air will be moving slower.

Q (flow) = V (speed)* A (cross sectional area)



there are also flow restrictions induced by the fittings and piping (drag) which take up some of that flow energy in the form of heat, which is insignifigant with air flow.



but basicly if you have the same fitting on the end, and you aint extending the hose an extra 15 feet it's not going to make a whole bunch of real world difference in suction