Shop Vac Hose diameter and suction

[Kris R]

I have a 6hp Rigid shop vac with the 2.5 in hose. The hose is short and not very flexible. I about to order a custom 30' flexible shop vac hose for this vac. Buying 30' in 2.5"diameter is not only expensive but it will take a lot of room. I want to go down to 1.5 or 1 7/8th inch hose. Its more maneuverable in a vehicle interior. But my question is will the suction be increased or would it cause too much resistance and actually decrease? I don't mind if it stays the same or increases I just don't want to lose any suction. Thanks!

[MikeLW]

When you decrease diameter of hose with all other things being equal, it doesn't have to overcome as much area to pump air to create vacuum. You will be fine with 1.7/8ths hose diameter.

[ski2]

I have a Craftsman 5 hp vac that came with a 2.5" hose. I have switched over to a 1.25" hose as you say because it is more manuverable in the car and find the suction is not as great with the 1.25" hose, but sufficient.

[MikeLW]

When you decrease diameter of hose with all other things being equal, it doesn't have to overcome as much area to pump air to create vacuum. You will be fine with 1.7/8ths hose diameter.

There is a point where the pump will become restricted when the hose diameter is too small for the given application. I forgot to mention.

[SR99]

If you're just vacuuming up dust and small particles, your "6 HP" (haha) vacuum should probably be OK even with the long hose length and smaller diameter. If you're mainly picking up heavy debris like wood chunks in a wood shop, the increased friction from the longer and narrower hose may make it so the vacuum motor has a hard time pulling it the length of the hose, and you might have to pick up the bigger/heavier debris manually.

Here are some rules of thumb for hose diameter and length versus vacuum motor size (I'm guessing your "6 HP" vacuum has a single 3-stage vac motor). These numbers should be conservative since they are for a carpet extraction application where you have to transport water sucked out of the carpet through the hose (which is a lot heavier than if you're just sucking up small, dry debris)
What is the recommend maximum length of hose I can use with my extractor (http://www.steam-bright.net/showthread.php?53-What-is-the-recommend-maximum-length-of-hose-I-can-use-with-my-extractor)

(forgot to add that keeping your filter clean can make a big performance difference too. All bets are off if your filter is fairly clogged)