Replies

1. 
   forestgirl | Mar 17, 2008 06:41am | #1

   What DWV?  I know about S&D (Sewer and Drain), but haven't heard of DWV.

   forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 
   
1. 
   seajai | Mar 17, 2008 06:43am | #2

   DWV= Drain Waste Vent 

2. 
   BarryO | May 09, 2008 01:36am | #3

   I use ABS DWV, and have it installed under the concrete floor.  It's considerably stronger than either PVC S&D pipe or metal HVAC ducting, so it's a good choice  for this application.

1. 
   jrsosa | May 09, 2008 03:06am | #4

   BarryO

   What size did  you install and what size is your DC?

    

   Thanks Jerry S

1. 
   BarryO | May 09, 2008 08:59pm | #8

   It's 4".

   Many people quickly read the Bill Pentz site, and say "you need to run 6 inch pipe or ir won't work".  But if you read carefully, it's not that simple.

   4" pipe will support a 400 CFM flow with a reasonably-sized DC.  If you look at the chart on Bill's site, that's the flow that is required at the dust port on most tools.

   But some tools need two ports for efficient dust collection; e.g., table saws, which need 400 CFM at the cabinet and 400 CFM at the blade guard.  That's 800 CFM.  If you sum the flow from both ports together into one pipe, you need one with about twice the cross-section.   6" pipe has (6/4)^2 = 2.25 times the cross section of 4". so it will support that flow.  But so will two 4" pipes in parallel.  So I just run a second 4" for those tools that need them; e.g., the cabinet port on the TS goes to the underfloor 4" pipe; the port on the guard, which is overhead anyway, goes to the ceiling.

   I get by with a 2 HP DC.  My runs are relatively straight.  I don't use a cyclone, so I don't suffer the statis pressure loss inherent in using them.  Also, I don't use a filter bag but instead blow everything outside, so I don't get the backpressure from using a bag. 

3. 
   AZMO | May 09, 2008 05:10am | #5

   I used PVC drain material for mine. In the 8 weeks since it has been installed (overhead) not under the floor, I have had some chunks of wood etc get caught. The worst culprit is a bit of paper or plastic from a hardware bag etc. You really need to plan on how to clean out the system if it gets plugged. An underfloor system lets things fall in easy, but how do you get them out?

   Years ago I used a school shop in the evenings for an adult class. They had an underground sawdust collection. Well it was a receptacle only, completely plugged up and no way to clean it out. More worthless than a $2 dollar bill. The instructor was frustrated and advised all of us not to install under the floor.

   I would urge you to consider going overhead and do not glue the joints. Just tec screw so you can dissamble them. Over size the pipe, I used 6" and reduce only at the flex line to the machine. My 1.5 hp Delta with a .5 micron bag moves as much volume of air as a direct connect.

   Best place to review dust collection is http://billpentz.com/woodworking/cyclone/index.cfm Which is quite the missive, but worth reading!

   Good luck AZMO

                     

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   -------(*)/ (*)   http://www.EarthArtLandscape.com

1. 
   Don01 | May 09, 2008 09:17am | #6

   Hi Morgan,Why not get some light grating, the expanded metal type - aluminum, and fab up some suction inlet screens?
   The small portable "blower with a bag" units have that type of screen right at the blower suction inlet.Don

1. 
   AZMO | May 09, 2008 04:01pm | #7

   I have mine set up with a y tee at the portable DC inlet. I has some long nails going through on a criss cross pattern. I open the plug and reach in a pull out the plastic bag, chunk of wood, trimed edge from the TS etc etc. Works great. I would never want a DC duct work under a concrete floor. A wood floor with crawl space, now that would be great way to have a DC system.

   AZMO                  <!----><!----><!---->

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   -------(*)/ (*)   http://www.EarthArtLandscape.com

2. 
   doctom | May 12, 2008 04:06pm | #9

   I disagree that there would be no way to clean an underground system. Schedule 40 DWV ABS is made to go under concrete floors and is commonly used as sanitary drains. These drains do get clogged and are cleaned with mechanical sewer cleaners all of the time. The ABS stands up well to this cleaning.The very smooth interior and joint connections of a properly installed ABS (or PVC) system provide very little in the way of resistance to start a blockage, especially with proper air flow. And without proper air flow, a dust collection system system doesn't work anyway.It may well be that a high school shop system was plugged by vandals, but in my shop, I can easily ensure that I don't get anything near the intake that couldn't pass through my system.

1. 
   AZMO | May 12, 2008 04:43pm | #10

   Sanitary sewers are great, lots of liquid that slides around.

    Any pipe system that is cut and inserted into a fitting has a protruding lip left on the pipe. One piece of small trim from the cut off of your Table saw will drop down and into the system. Inadvertent but it will happen. That piece travels the pipe to a tee or 90 and can catch on the protruding pipe lip. It will at some point. Then other pieces catch and hang up. After some time it becomes plugged. If you use a floor sweep port, which I think are the Cat's Meow, then it easier yet to introduce the wrong material, especially when you are tired.  Then you will need to use a rotor rooter tool to dislodge the mess, and being in construction, I have seen pipes where they could not unplug them. Sawcutting concrete is no fun.

   My advice was to provide some service points so that it can be cleaned out, or go overhead so that you can service the system by simply undoing an unglued fitting. To each there own, but I really don't think I would like to rotor rooter my DC system.                  <!----><!----><!---->

   -----------_o

   ---------_'-,>

   -------(*)/ (*)   http://www.EarthArtLandscape.com