Pointers on blowing a pull string through conduit

[CM1995]

OK here's the deal - I am bidding 1000' of a double run of 5" conduit (2000' total) and 250' of 4" conduit. This is a commercial development, easy access and we will running behind the curb in the ROW. There are 2 curb cuts but the seal coat has not been laid so patching will be easy.

I have ran a lot of shorter runs of 3,4 and 5" conduit for building services and 3 phase transformer pads but never had to install a pull string in them because they were short, from service pole/pedestal to the building. I have the specs from the power and phone co and I am comfortable with the project as far as the digging, conduit installation, etc goes.

My question is how to go about blowing your pull string. There will be 3 pull boxes along the route, approx, 300+/- ft. I have seen Asplundh use little parachutes and I have seen other people use a ball of tapped up rags. I have never done this before, only watched other folks on the jobsite do it.

Any tricks or pointers on how to blow a pull string through conduit? Thanks in advance.

 

[TheOldMan]

Greenlee makes a "mouse" made from foam rubber that you tie your line to and suck through with a vacuum cleaner - works great.

 

[jxm7202]

i always used a piece of grocery bag taped to a string, and a cordless dewalt vacuum. never tried it on a conduit bigger than 2" though. i think your biggest problem is finding a piece of string long enough. i always use string line string which is 260' rolls, i have tied a few together before.

 

[Trashman]

I use a fishing bobber that is just small enough to fit in the conduit. Attach the bobber to the string and then pull the bobber through the conduit with a shopvac

 

[boaterri]

A shop vac with the "mouse" works well as long as there is no water in the line. The water will stop what ever the ball is on the end dead.

Good luck,

Rick

 

[sstocker31]

I used to do this some time ago, with similar runs as your going to do. We used something similar to the "mouse" "TheOldMan" suggested. If you can picture a foam rubber ball with a plastic/metal tail that goes through the centre of the ball and extends 8 or 10 inches behind the ball. We tied our string to this tail and then shoved the whole thing inside the pipe. Next we set up the string to spool freely off the roll and then sealed up the pipe end just leaving enough room for the string to move freely and to stick the end of a jackhammer hose inside.....fire up the compressor and it will shoot that thing through there like no tommorow.....just make sure a piece of plywood is setup at the other end so the "mouse" has something to bang into so the other pipes in the basin don't get damaged.

Thats how we did it....never any problems

 

[stumpjumper83]

why not just put the rope in as you go? Just set a spool of well rope where you start, tie the end to a 12 cressent wrench and chuck it thru the joints of pipe as you go.

 

[FRISKY]

why not just put the rope in as you go? Just set a spool of well rope where you start, tie the end to a 12 cressent wrench and chuck it thru the joints of pipe as you go.

That works as long as the pipe uses O-rings and not glue to put the joints together.

 

[digger242j]

why not just put the rope in as you go? Just set a spool of well rope where you start, tie the end to a 12 cressent wrench and chuck it thru the joints of pipe as you go.

I'd sooner use a piece of rebar, maybe 10 feet long, because that way the end is already halfway through the section. You don't need to chuck it as hard.

That works as long as the pipe uses O-rings and not glue to put the joints together.

We've done it with the glued type too. You just need to be careful to be sure it's still free after each joint you put in.

A shop vac with the "mouse" works well as long as there is no water in the line.

...stick the end of a jackhammer hose inside.....fire up the compressor and it will shoot that thing through there like no tommorow...

I saw a guy from the cable TV company get an unexpected shower one day with this method, cause there was water in the line. :roll Stand back...

 

[dirty4fun]

We have used the grocery bags, with the twine that comes in a box fro pulling wire. A shop vac on the other end, it doesn't take long at all. Has always worked great.

 

[stumpjumper83]

I've never had any problem with glue on the rope, if your doing it right your moving all the time and that glue is specially designed for the pipe, not the rope.

 

[digger242j]

I've never had any problem with glue on the rope, if your doing it right your moving all the time and that glue is specially designed for the pipe, not the rope.

I never did either, although once I got the string (cause it was a "string", like mason's line), somehow caught in the joint between the two sections.

 

[WColtharp]

Now after reading some of these responses I might have to try one or two out at work, thanks guys! We usually just cut a 20 oz bottle in half and use it as a kite to carry the string down the pipe while pushing air through the line with an air compressor. Granted this is usually with smaller sewer line, but it seems to do the trick!

 

[robin yates uk]

the Irish lads doing Telecom in the uk used a tightly wadded plastic with the draw cord firmly attached to the middle, then blow it through with the compressor airline. I have seen them do 600 metre runs like that.

 

[nedly05]

Ive worked on jobs where we used a hooked the string to a ping pong ball and pushed it through with a leaf blower, then tie the pull rope to the string, hook the string to a dowel in a cordless drill and while winding the string up on the dowel, you pull your pull rope through. Works well.

 

[FP-Z71]

I worked for a crew that did the rebar trick, but we used mule tape because we had to pull uphill, worked great, never had the tape get stuck in the joint.

Muletape

 

[buckfever]

We use pull string that comes in 5200' five gallon bucket. For a parachute we use plastic that they use for packing. That stuff thats like heavy-duty plastic wrap. For pulling the string we use a shop-vac, this works really well and it also help get any small rocks or pieces of dirt that got in the pipe when you were putting it togeter.

 

[CM1995]

Thank you all for the responses.:thumbsup I have worked two 14 hour days and I am dog tired.:dizzy, so I will be working on this bid this weekend. Keep the info coming, it has been very helpful.

 

[JDOFMEMI]

CM

I have done many of these jobs. I would leave trhe shop vac in the shop where it belongs. Also the crescent wrenches, rebar, packing tape, and so forth.
Your pipe distributer will have a proper sized mouse for the job. It is a rubber cone, with a metal rod to tie the string onto. You get a blow up plug, like a sewer test plug, with a fitting for the air compressor hose, a ball valve for control, and a wye with a small hole in a plug to feed the blow string in. Blow string is about 1/8", and lightweight. It is cheap and I always considered it an expendable item. As mentioned above, protect the other pipes in the pull box from damage, as the mouse is really traveling. The rate can be controlled with the ball valve and an eye on the string feed. If it is moving too fast, choke the air down a bit. Still, no one should be in the box at the other end.

On most of the lines I ran for the power and phone companies, they had to be mandreled after backfill, to test for crushed or deflected pipe. Again, your pipe supplier has these. Usually the mandrel spec is 1/4" smaller than the pipe. Say 4-3/4" for 5" conduit. On most of our power conduits, proper pull string had to be placed after the mandrel test. Pull string, as opposed to blow string, is a heavy duty rope, with foot markers on it so the true length is verified prior to pulling the cables through. The pull rope we were required to use I believe was 1100# test.

 

[digger242j]

I have done many of these jobs. I would leave trhe shop vac in the shop where it belongs. Also the crescent wrenches, rebar, packing tape, and so forth.

Leave it to a professional to stifle everybody's creative energy....