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Thread: Is it really necessary to tape the pvc joints of your DC plumbing?

  1. #16
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    Use silver/grey PVC tape. We call it duct tape here in Australia. It is flexible and behaves similarly to PVC electrical tape. It stretches into place and is easily removable if required with no residue. Keep it out of the sun and it is good for years. As an aside, what you guys call duct tape, we call 100mph tape and use it to patch bodywork on race cars. Cheers
    To break the rules, you must first master the rules.

  2. #17
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    Quote Originally Posted by Mike Dowell View Post
    Provided you aren't rich and can't afford plumbing such as NordFab, do you tape the joints in your PVC pipe? I'm about to buy the Clearview 1800 DC, and most of the youtube videos I see portraying PVC plumbing show the joints being taped. Seems like they are a pretty good fit to boot though.
    Who knows "necessary"? Taping/sealing could decrease losses but buy how much? It may be a matter of degree. My 5hp ClearVue is so powerful I can accidentally leave a second blast gate open and don't notice a big performance hit. I suspect that even if all joints leaked a little you would not detect a difference if measuring air flow/suction. Also, press 6" PVC into a fitting and it fits very tightly, quite difficult to get apart and the suction can only make it tighter.

    That said, I either glued or used aluminum tape all joins in my shop attic space. Since the most likely thing to need changes are the fittings and gates near the machines I fasten those with short self-tapping screws, three on each joint. Works for me.

    JKJ

  3. #18
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    Quote Originally Posted by Mike Dowell View Post
    Provided you aren't rich and can't afford plumbing such as NordFab...
    Many of us have used 26 gauge snap lock steel duct very successfully. Much less expensive than NordFab if you buy it locally from a sheet metal shop or an HVAC dealer, approaching the cost of thin wall pvc. AFAIK only hobbists use pvc for duct. Still baffled as to why so many think the only two choices are NordFab and pvc.
    Last edited by Ole Anderson; 07-14-2017 at 10:31 AM.

  4. #19
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    Quote Originally Posted by Dan Friedrichs View Post
    Silicone caulk. Easy to remove, later.
    +1. One screw and smeared some caulk around the edge and called it done. No leaks.
    Wood: a fickle medium....

    Did you know SMC is user supported? Please help.

  5. #20
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    Quote Originally Posted by Ole Anderson View Post
    Many of us have used 26 gauge snap lock steel duct very successfully. Much less expensive than NordFab if you buy it locally from a sheet metal shop or an HVAC dealer, approaching the cost of thin wall pvc. AFAIK only hobbists use pvc for duct. Still baffled as to why so many think the only two choices are NordFab and pvc.
    Not sure that being a Hobbyist is linked to the choice of PVC :-) I changed from snap lock steel to PVC because it was cheaper, easier to assemble/cut and has a smoother, slightly larger internal bore resulting in better flow. If I were in business (assuming there was no issue with insurance) I would choose PVC for the same reasons

  6. #21
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    Not too sure about this hobbyist and pvc connection either. It's a choice of cost vs return and that's all. In fact in my shops I have always used a combination because steel is cheap for the big bore stuff and pvc is cheap for the smaller stuff.

    I tape joints so they don't rattle apart. However they are still easy to pull apart to clear the occasional blockage. Cheers

  7. #22
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    I use three short sheet metal screws in each connection now. I used duct tape in the past but I got tired of having to clean the tape off of the fittings when I had to modify my system and the screws keep the joints tight even when there is vibration. I installed a DC swivel ball where my CNC Router hose connects to the pipe because the hose is constantly moving as the gantry moves all over the table. I also have a swivel joint at an overhead connection point that I use for my planer and other temporary connections like a long hose for floor sweeping.

    When you have the proper penetration PVC pipe joints don't leak, the screws assure that they stay tight.

  8. #23
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    Quote Originally Posted by Andy Giddings View Post
    Not sure that being a Hobbyist is linked to the choice of PVC :-) I changed from snap lock steel to PVC because it was cheaper, easier to assemble/cut and has a smoother, slightly larger internal bore resulting in better flow. If I were in business (assuming there was no issue with insurance) I would choose PVC for the same reasons
    The issue you would run into as a business would be if you ended up with employees and came under the watch of OSHA...PVC isn't permitted for dust collection, if I'm not mistaken, in a commercial environment.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  9. #24
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    Quote Originally Posted by Dan Friedrichs View Post
    Silicone caulk. Easy to remove, later.
    I agree! Looks better too.
    No PHD, but I have a GED and my DD 214

  10. #25
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    Pvc tape is amazing stuff.

    Also gorilla tape is amazing too.

    I have not used either on ductwork but great products mentioned here.

    Anyone use butyl caulk? That is some super gummy stick stuff. Harder to remove but sprsy technologies used some on this new to me cyclones fittings and it did a great job sealing the hoses to fittings.

  11. #26
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    Quote Originally Posted by Mike Heidrick View Post
    Anyone use butyl caulk? That is some super gummy stick stuff. Harder to remove but sprsy technologies used some on this new to me cyclones fittings and it did a great job sealing the hoses to fittings.
    Using a pure silicone caulk, it is easy to remove later if you need to modify things yet it seals nicely.
    Wood: a fickle medium....

    Did you know SMC is user supported? Please help.

  12. #27
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    100% silicone for sure. Do not use latex or siliconized latex- too hard to remove. 100% silicone rubs off easily. All you need is a small, thin bead on the outside of joints- remember your duct is under negative pressure which pulls the caulk tighter.

  13. #28
    I'm not very learned on such things, but wanted to throw in my $.02.
    It seems to me the far bigger problem is on the inside, turbulence and head.
    I watched a show once where they demonstrated a new way to repair broken/cracked sewer/water lines with a membrane that they simply blew into an open end of the pipe and expanded it. The result was a pipeline as good as new.
    Not having tinkered much with conduit to transport air, I have afair amount of experience dealing with head on the pressure side of a water pump.
    For many years I kept koi and efficiently of the movement of the water column was where it was at.
    Most "well designed" systems used as few fittings as possible to limit head. And, when possible, fittings are not used. The pvc would simply be heated slightly and bent into the position required.
    Seems to me the membrane I mentioned would achieve nearly the same thing. This would also eliminate the need to tape anywhere on the outside.
    Perhaps there are those here with the wherewithal to even apply a thin film on the inside of pvc,perhaps by spray gun to achieve the same thing
    But as I said, we're talking water vs air.

    By the way, this may be common knowledge here at Sawmill Creek because there seems to be an unusually high number or great minds here, and this really has nothing to do with pulling/pushing air, but race boats do not strive for a perfectly smooth hull
    They use a specific grit of sandpaper to create an environment for air to accumulate. So, the boat skims across the water on a very thin layer of air, reducing drag.
    May not be worth $02, but wanted to throw my thoughts out there.

  14. #29
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    There isn't much you can do about internal turbulence and static pressure other than design duct runs as best as you can with minimal bends and fittings, optimize duct size, and use a blower designed to achieve the desired CFM with the duct SP restrictions.

    There are a whole host problems with a "liner"- first and most important- liners are designed to seal against leaks with pressure on the inside of the pipe- dust collection systems work with negative pressure on the inside. You seal the joint to keep air from leaking into the duct. It is most likely too difficult and I'm sure way too expensive to install a liner that would need to be rigid so it won't collapse, and frankly that level of sealing is just much easier and cheaper to do by other means from the outside. What do you do about openings for branch ducts and drops? How does it handle bends and wyes? Won't it be difficult to disassemble to change your duct configuration (a fact of life in most shops as people get more machines). And last but not least, high velocity wood chips would likely wear it out or tear it up in pretty short order. Also, a liner reduces the effective I.D. of the duct. I've never heard of any hobby or commercial use of such a liner in dust control ducting.

  15. #30
    I'm not trying to be contentious....just thinking out loud.
    I know koi keepers who would chase ideas to the ends of the Earth.

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