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I am working on sending some cables (RG6, Cat5 and speaker cables) from basement to the attic. This is a typical 2-story house.

After reading some posts found over the Internet, I am now considering to build a conduit using PVC pipes. The conduit will be 3" in diameter, enough to put many wires inside.

However due to the location of the utility room, as well as the wall chosen to embed the conduit, it will have 6 bends in a total length around 55 feet. I am little bit worried about I really can add wires through this conduit after I build it, considering that it is quite long and has 6 bends in the total run.

What is your opinion? Thanks

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  • Are the bends inside the wall? If so, how do you plan to install? are you opening up the wall?
    – DA01
    May 22 '15 at 16:53
  • If you open things enough to run conduit, don't put the cables you're running NOW in it -- leave them strapped to the outside. Cat5e, RG6 and speaker cables have been and will continue to be useful for years. The conduit is for new cables you don't know you need (or don't exist) yet. You may also want mechanical protection, but that's probably better done with either a separate conduit (where needed) and/or strategically-placed nail plates.
    – gregmac
    May 22 '15 at 21:32
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This is actually quite simple.

Step one - use PVC electrical conduit, not PVC pipe.

Step two - provide an access point (such as an LB, or a junction box) for every 360 degrees (at most) of turn. This will be something that remains accessible by removing a panel when the walls are closed back up, like any other junction box access.

If you have 6 90 degree turns, either put in 3 90's and an access point (if using an LB, that can be the access point) or 4 90's an an access point, depending how the run works out best for placing the access point. Use electrical conduit sweeps, not plumbing 90's or 45's.

3, access point, 3 would be most balanced, but

4, access point, 2 is also fine.

There's no need to get too excited about leaving a pull string in place - you can always vacuum one in, or pull one in while pulling an old cable out. Do it, or don't do it, as you prefer. Do make sure that the ends of your conduit terminate in junction boxes from which the cables leave by fairly tight holes or grooves (or through proper cable clamps, but that can be tricky with pre-terminated cables), so that your conduit does not become your new rodent pathway and nest.

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While you're building the run, you can put a chase string in place, and use it to pull cables.

You'll want a chase string to be 2x the total length of the run, and tie it off to each end of the run by tying it to an eye hook or a screw.

Then it won't (generally) matter how convoluted the run is, you'll always have the chase string to guide wires from one end to the other.

I like to use mason's twine for chase string- tough enough to not break, but supple enough to go anywhere.

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    I would also suggest adding a backup pull string just in case the first one fails.
    – Jason Hutchinson
    May 22 '15 at 19:22
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I'm assuming you're talking about not using proper plastic electrical conduit.

If you want the capability of adding wires later, it sounds like the only solution with that many turns. Be sure to use the longest sweeps you can - normal vent 90's will not work. Many manufacturers make extra long sweeps for regular pvc that is not in the home center - hopefully you can find a supplier for these that will send you just 6.

Alternatively, you can use paired 45's or even try bend your own using a high-end heatgun - but with 3" pipe, that's going to be rough.

After the run is created, be sure to leave a leader in the conduit for ease of pulling new cable. One way to do this is to snake a length of string clear through the pipe and attach the string to the other end of the conduit (leave the string attached to the spool). Pull the snake out and tie a loop in the string at the starting point (plus a 2' of slack, then pull this through the conduit as well until the loop comes out the other side). Finally, with the loop at the far end, cut the sting off the spool and attach the string to the conduit. Neatly gather the extra at one end and leave it there. This gives you a string to shuttle wire back and forth the conduit without snaking it every time. Occasionally, replace the string if it starts to look worn.

There are other ways to shuttle as well. Any way you do it, the conduit is key and will make the task of upgrading very easy.

Note - I believe code requires you not to mix high and low voltage wires in the same conduit, so don't plan to use this to run new outlets later on.

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Don't worry, you can do it. There is a special tool that can be used to install a pull string in any 3" pipe no matter how many bends. It looks like this:

hamster

Be sure to use lots of lubricant when you do the pull. Hmm, that came out sounding wrong.

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I would try to include a couple of PVC cleanouts at a couple of the interior bends, ideally evenly spaced (eg. bend - cleanout - bend - bend - cleanout - bend). This way you could start a cable and pull it through the cleanout before feeding it back in and pulling to the next cleanout. This means each pull only has to traverse one or two bends at a time, cutting down on friction and lessening your chances of damaging the wires.

Incorporate TX-Turner's suggestion and include the chase string between each cleanout.

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Depending how many bends are in the conduit it can be difficult to pull wires. Not having more than 360 degrees in the total is a good rule to follow. So as long as all your bends (90 degrees, plus 90 degrees, plus 90 degrees etc..) doesn't add up to more than 360, it should be good.

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