How can I pull a wire through a pipe that has too many turns for fish tape?

36

6

I need to replace a sump pump, but have run into a problem. The route for the cord goes through a 2" pipe with two 90 degree bends, and fish tape is ineffective. The pipe appears poorly jointed as well and uneven. Is there a way to get the cord through this convoluted pipe?

The old cord is already out of the pipe, and cannot be used to drag a pull string.

Getting a power cord through a pipe with many turns without fish tape

Bryce

Posted 2016-10-02T00:51:06.423

Reputation: 7 140

7I once managed this by shoving a cheap metal tape measure through a pipe like that. The tape wants to stay straight but will buckle neatly at the bends and continue on it's way, then pull it back through with a cord attached.Wossname 2016-10-02T09:41:38.950

3I wonder if a sewer snake might work better.Hot Licks 2016-10-03T01:38:53.457

1I don't have any wiring to do, but the answers seem so fun that I could try them anyway...algiogia 2016-10-04T10:50:46.373

@HotLicks I tried a sewer snake. No possible way. In fact even that cord end in the picture would not go through WITH a pull string, until I pulled another trick or two. -OPBryce 2016-10-04T15:09:37.397

Answers

73

This technique worked great. I tied a string to the cord, tied a plastic bag to the string, and sucked that bag right through the pipe using a vacuum cleaner.

plastic bag as fish tape alternative

Just be a little cautious: the bag can travel through the pipe in a blink of an eye, and you might not want to have to fish the bag out of the vacuum.

Once the bag is through, pull the cord through, and untie the string.

Bryce

Posted 2016-10-02T00:51:06.423

Reputation: 7 140

2Electricians have small foam plugs called "mice" that they use for this -- probably easier to work with than a plastic grocery bag.ThreePhaseEel 2016-10-02T01:24:04.890

6You can solve the problem of sucking the bad by using some sort of mesh at the end. Air-confitioner filters could work great with this. Also, for situations where the vacuum cleaner tube is too small, you can use a paper sheet with a hole smaller than the vacuum cleaner's tube diameter.Ismael Miguel 2016-10-02T11:41:47.343

2Or just duct-tape 2 pieces of rope in 'X' fashion to tube's exit if you don't have a mesh on hand.Daerdemandt 2016-10-03T09:43:37.830

I've made a bullet to do this using the tapered part of a marker pen. A light ball (ping pong ball or smaller hollow ball from a toy) also works well. You can get more suction by removing fine filters from the vacuum, but keep something to protect the motor. There is an upper limit to the bends you can get round this way -- if it starts to resemble a coil, the fish string will pull tight.Chris H 2016-10-03T13:02:41.513

1@ThreePhaseEel foam plugs have their place I suppose, but this is a DIY site, no? Gotta give a star or two for using materials on hand. This by the way took all of like 60 seconds start to finish, including finding the bag, it went very easy.Bryce 2016-10-04T15:14:13.323

@Bryce -- yeah, definitely a +1 for the bag-rat xDThreePhaseEel 2016-10-04T22:17:22.713

25

As a wireman with 30+ years of experience, I've had to do lots of tricks to complete the task. While a vacuum and rat (plastic bag) works most of the time, it sometimes fails for many reasons. You might want to go the opposite of that idea. Get some nylon string and a living rat from a local store. Be sure to size the rat for the specific size conduit. Get some compressed air from somewhere. I have known them to run 1/4 mile before. And the rat will go fast. Have a helper to dole out string as it enters the conduit. It's best to have a good lead laid out on the ground, because when you start, the first hundred feet will be run in seconds. Good luck

user60794

Posted 2016-10-02T00:51:06.423

Reputation: 251

18Just remember to feed and water the rat and release it when finished.Chloe 2016-10-02T21:21:38.623

1I've no idea if this would work consistently (what if the rat stays in the middle of the system?) but it's ingenious even if it doesn't.enderland 2016-10-03T18:35:33.550

14@enderland If that happens then you need to use an electricians snake to get the rat out.Freiheit 2016-10-03T18:37:30.007

5@Chloe That's silly - why would you simply release a rat after having gone through all the trouble of training it to pull cables through things?Crashworks 2016-10-04T01:27:59.690

1Amusingly I believe weasels have been used to pull wiring in planes before?!djsmiley2k 2016-10-04T10:03:18.940

5@djsmiley2k, yep, trained ferrets were used by Boeing to drag the pull cord for air liner wiring runs. I don't think they do it any more -- not since the Federal Ferret Workers' Union strike of 1964.Wossname 2016-10-04T13:49:13.447

1This is a joke answer, right? What motivation does a rat have to pull your string/fishwire/whatever for you? I had to make sure it wasn't April 1st!Nick DeVore 2016-10-04T17:53:16.410

15

Another trick that works is to use weed-whacker line. It's essentially really thick monofilament and it turns corners better than fish tape. I've used a lot of it on my boat to pull wires.

Eric

Posted 2016-10-02T00:51:06.423

Reputation: 251

Heavy fishing line might or might not also work; same idea.keshlam 2016-10-03T00:38:42.073

PTFE-insulate wire as well.Chris H 2016-10-03T13:03:24.410

7

In the past I have used

  • micro RC cars - tie the string to the body and drive.
  • hexbugs - (A hexbug is a small oscillating, buzzing "robot". The oscillation in combination with its flexible rubber legs makes it move.) tie a string to it (lightweight monofilament) and go for a cup of tea, come back when the bug has gone through the conduit
  • magnets - one tied to the end of the string one outside the wall to pull it through the pipe, doesn't work so well on ferrous pipes :D
  • hoover with a bag and string - as described above
  • small fishing float - tied to a light line, close the "bottom" end of the pipe, flood it and watch the float come up voila pipe traversed.
  • leaf blower and bag and string - similar to the vacuum, more fun to do though, and seems to develop more pressure for pushing the bag.
  • bearded dragon - put him in one end, release live food at the other and off he goes.....just remember to tie a light string to a harness or its basically just a fun run for your lizard! (guilty!)

Hopefully some of these can help you, maybe not the bearded dragon for that size of pipe though.

GMasucci

Posted 2016-10-02T00:51:06.423

Reputation: 179

1Suction is limited to 1 atmosphere (which cannot be realized), while pressure is not. Same problem as pumping water up out of coal mines: pushing works better than pulling.Yakk 2016-10-04T13:15:16.543

Thanks, never looked at why the leafblower was so good, but that certainly explains it:) I have tried industrial vacuum generators, with the sometimes funny side effect of collapsing the piping (not so funny when it has to be replaced, but makes the walls look rather cool:)GMasucci 2016-10-04T13:25:46.507

@GMasucci : gecko. Have you ever tried a gecko? Of course that animal is nocturnal, so you'll have to tie the string, put him in, and he'll hide in the pipe until nightfall. Come out at night with a flashlight and grab him....Bryce 2016-10-04T15:12:30.303

Lol not tried a gecko, though they can climb on just about any surface so might be worth a go, and I get a new pet out of it:)GMasucci 2016-10-07T13:48:15.233