TWO vacs in parallel

Hi Y'all,
I've been away for a while, but I'm spending more time in the shop again and have more to share.

About a year ago, I posted photos of a massive cart I built to carry my dust deputy and vacuum. This is an update to that post.

http://www.routerforums.com/show-n-tell/89578-i-kicked-bucket-man-sucks.html

I still love the dust deputy, but the cart was always in the way. I finally moved it to the crawl space under the floor (about 4 feet of vertical clearance) and piped the suction up through the floor in several places. I just plug the ones I'm not using.

I really like this setup, but now, in order to vacuum the floor in the farthest corner, I must hook together 3 seven-foot hoses. All that piping and corregated hose cut the suction down to where it would pick up, but so slowly it missed some.

So, I dragged my spare vacuum under the shop and hooked it up in parallel with the first. I added a flapper-type check valve in line in front of Vac #2 so Vac #1 can be used alone without backflow through #2. I have two switches in the shop so I can turn on either or both vacs. With two vacs running, I have excellent suction even at the end of 21 feet of hose and a lot of piping and elbows. I'm really pleased with the result. If I'm sanding, I can use vac #2 alone. some air will backflow through vac #1, keeping the suction at the sander down and helping cool the running vac.

Here's a schematic of the setup and a picture of a vacuum stub in the shop. Might give someone an idea . . .