First post here, so be kind
I have 450' of 3" schedule 40 electrical conduit in a 36" deep trench. Total of maybe 340 degree, 90s are 36" sweeps. All covered now with wire arriving on Tuesday.
So today I tried to pull the leader string. Started with a crumpled up paper tied on the string at the uphill opening, shop vac at the lower opening. Seemed to pull in just fine, but when I came to the end of 600' of string, I figured I may have an issue.
Pulled it all out and replaced the paper with a 2" styro ball on the string. I also reduced the end of the 3" conduit to 2" at the string end and taped the shop vac in the lower conduit opening. Same exact thing, pulled in 600' of string until I stopped. If I try to pull the string back out, with the vac running, I get a very slight tension, like I am pulling the ball, but maybe not.
Eventually the entire string and ball come back out.

I think one of a couple things has gone wrong:
I may have some glue drip, preventing the ball from going any further, but still leaving an opening for the vacuum to pull the string. Thought here is to just keeping dumping string in until the loop of string comes out the other end.
Failing this approach, I am thinking of a towable compressor, hooked at the top opening and dump air into the conduit, hopefully pushing the ball by any obstruction.
May be rock, clump of dirt, partially collapsed pipe or even a dead rodent. Then I am clueless. Any suggestions?
Thanks

 

Welcome to the forums! How long has the conduit been buried? Have the ends been capped? You may be pulling against the flow of joints and it could be hanging up on the overlap. Can you pull the leader string in the opposite direction? I would try a piece of cloth rather than paper for a rat. I'd also try direct hard suction from both ends to see if something has occluded the conduit. It may take a rather large vacuum to do that, however.

 

I have had luck with a crumpled up plastic sandwich bag and braided fishing line, but I was pulling only about 220', but you could you try that.

Otherwise, I would hate to get the ball stuck in there trying to push it with compressed air.

Maybe try a "real" tool for the job like this: 3 Gardner Bender FC9 Foam Conduit Piston 3 1 2 in Grey | eBay

 

I have also used a leaf blower. A big backpack one can generate enough volume to even get a small thing moving in a big pipe. Once I had to drop all the way down to a foam earplug on the end of kite string.

 

It's too small for a 3" conduit. The mouse must be just slightly smaller than the ID of the conduit and just the typical shop vac may not be powerful enough for the length of conduit. Be prepared, once you get the string and then a pull rope in, 340 degrees of bends will be a hard pull.

 

Especially if you didn't use steel 90's.

 

I'm lost..... you have 450' of conduit and 600' of string wasn't enough ?

I've pulled way over 450' with a central house vacuum and a large garbage bag.
You are using the poly pull line....right ?

Don't use a ball..... it WILL get stuck. Use a plastic bag or a pull mouse like Tolyn mentioned.

 

PJ, I think what has happened is the string was sucked past the 2" ball. Just an assumption on my part, but I don't see how else the OP could have pulled in 600 feet of string.

 

That what I was thinking but what was holding the string bound on the first pull when he used crumpled paper ?

The paper has no strength.

 

By all means use poly string for ease of pulling and strength. You can find it at the box stores or at electrical supply houses. Kite string won't cut it. Last pull I had, I let my new helper do it. It was only 100 ft, but after a minute or so, I told him to stop. He had 250' or poly string in the vacuum Bird's nest.

 

Masons string will cut through PVC like a saw blade, especially the 90s.

 

Just an update: Went with poly string and a plastic bag pulled by an shop vac. Worked like a champ! Run the mule tape and got the 2/0 conductors pulled in just fine. Actually we didn't even need to pull, just pushed by hand!

 

Glad you got it worked out. Sometimes little adjustments mean all the world. Welcome back anytime.