How to Make A Simple Shop-Vac Muffler

shop vac silencer stuffed with towels noise reductionSo, how do you make a muffler for your Shop-Vac?  It’s really not that hard, and I’ll walk you through everything in this post.  This is kind of part 3 of me installing Shop-Vac for my CNC router, so be sure to see part 1 – the CNC router holder, and part 2 – an overview and results of how I reduced the Shop-Vac’s noise.

The muffler/silencer cost around $20 to make, but some of the smaller bits (like duct tape) were already on hand.  Here’s what I used to make it:

  • 10 inches of 4″ PVC pipe
  • 8 inches of 1″ PVC pipe
  • 4″ to 2″ PVC pipe reducer
  • 4″ pipe cap
  • 1 1/4″ to 2″ converter for Shop Vac
  • String
  • Zip Ties
  • Old towels

This would seem more shop vac muffler parts silencercomplicated, given all the “ingredients”, but once you have the pipes cut to the length specified, there’s not that much more to do.  Cut slits all down the 1″ piece of pipe to allow air to escape as freely as possible, and cut a few slits on one side of the 4″ pipe as shown in the picture.  The slits should be placed away from the vacuum to allow room for the sound to absorb as it travels down the inner pipe.

Wrap the 1″ pipe in towel or other scrap cloth, then slide it into the 4″ pipe.  It should fit without moving around too much, but it doesn’t need to be too snug.  The slits in the 1″ pipe should face the opposite direction as the 4″ pipe slits, so the air has a longer path to travel before it hits your ears.

shop vac muffler silencer configuration noise panellsCap the end of the 4 inch pipe closest to the slits, then put the 4″ to 2″ reducer on the other.  The towel can cover the end that’s capped, but try to keep the non-capped end free so air can flow into it.  Butt the PVC reducer up to the 1 1/4″ to 2″ Shop Vac part, and tape the two together so air can’t get out.  Plug this into your vac, then tie the string around the muffler and something above it or even the Shop Vac’s upper handle to provide support.

After using this for a bit, you may see the duct tape start to get holes in it where air can escape.  This won’t totally destroy your sound insulating capabilities, but to prevent this, you can tighten a zip tie around the tape to keep everything secure.  One thing that I haven’t tried would be to put a 90 degree elbow on the reducer.  This would allow the muffler to sit facing the ground, and possibly eliminate the need for a supporting string.  If it was made a bit shorter, it could possibly be made portable instead of fixed as seen here.  As to why you would want a fixed shop vac, check back for a post of me using it with my CNC router to remove MDF chips!

The disadvantage to using a system like this is a partial loss of suction (although it’s still pretty sucky), and seemingly more strain on the motor.  Like nearly everything else on Jcopro, this is highly experimental, and you should use your own judgement when constructing this.  I wouldn’t let it run totally unmonitored.  Another idea would be to build a box around it like this one.

Be sure to see the overview of this “silencing” project for the noise reduction levels achieved, and how I placed some panelling around the Shop-Vac to reduce the noise further.