3 inch emt........

Status
Not open for further replies.
C

chevyx92

Senior Member
Location
VA BCH, VA
Started a job today in a mall, where there is an existing 3" emt conduit stubbed into the unit where I am working. The run goes all the way back to the switchgear in the electrical room. The run is over 650 ft. with a pull box at about the 400' mark that has (2) 90's and (1) 45. I am having no luck sucking a jet line through. I am using a 5 hp shop vac and a field made head to suck through. I barely have any suction to get that line through. I have done this many times, not on a 3" pipe before but.. am I doing something wrong here? All fitting are set screw type. Do I need a bigger vacuum?
 
You may have a nasty blockage in there. :( As I posted here before, one time I had this same problem with a 2" because a bunch of dead mice were blocking the pipe.
 
Try suck an empty bread bad through the conduit with a nylon string tied on the bag.
I have used this trick many times. It works.
 
Duct tape the fittings or snake both ways with 200' snakes.

Leave one snake hook open and tie a bunch of folded over poly pull line on the other snake. I have good luck snagging one snake with the other.
 
We always use Bob's method, but if all else fails buy a fiberglass snake made for ducts. They come up to 1000' long.


rodder_1.jpg



http://www.contractor-books.com/KI/Tapes.htm
 
A standard shop vac only develops enough vacuum to lift a column of water 50"-60". A 2-stage vacuum will only go to about 85"-90". Greenlee's vacuums are 3-stage and will lift a column of water about 130"-140". With a conduit that large and set screw fittings if you do not have the Greenlee vac, (or another 3-stage vac), I don't believe you will be able to vac a string in.

If you have access to a nitrogen bottle, hose and nozzle (make sure the nozzle and hose have working pressure ratings greater than the pressure the Nitrogen comes with) then you could blow a string through. You would have to use some kind of a "Y" fitting between the nozzle and the conduit. Feed the string through a small hole in one section of the Y and blow through the large opening in the other section of the Y. A light plastic bag with the jet line tied to it should do the trick.

Don't forget to secure the area you will be blowing into. Safety glasses, etc. for the workers.
 
We have used a combination of both methods together on occasion -- Greenlee vacuum on one end and Jetline on the other end.

I agree with Don and Bob -- I'd duct tape all of the SS fittings that you can get to.

And I agree with HWS -- you'll never get there with a 5HP shop vac.

Or find an accessible point somewhere mid-way and separate the conduit at a coupling. Snake each way, tie the string together, and recouple the conduit.

We've had to do this every 100' or so on some occasions.
 
Hardworkingstiff,

Used trailer compressor before and it is unmatched.

I find that a "Kite" string works the best. It is light and thin for blowing mice or plastic bag.

We usually use compression type fittings. When using set screw type install the couplings on ten feet with clear silicon around one side. When installing the EMT put as much of a bead as possible around the other side.

Also used duct tape but this eliminates the need to remove the duct tape.

Justin J. Walecka
 
At this point, I'd rent the longer, fiberglass fishtape. I imagine taping all the fittings as it passes over the other occupied tenants would be a real PITA.

Goodluck
 
Well thanks for all the good sugestions guys. Today I did manage to get a pull strip through. I had one vacuum sucking on one end and another vacuum blowing the mouse through on the other. Worked really good. In response the last post, the 3" emt run was overhead. Thanks again.
 
3" dia.?

1. Small terrier with string tied to collar at one end;

2. Chunk of beef jerky at the other.

Problem solved. :D
 
had a short (125ft) run of 2 1/2 inch that we were having a real hard time with. The solution that worked was to tape a matchbox car to the end of the fish tape and "drive" it through the conduit. I was amazed at how well it actually worked.
 
Status
Not open for further replies.
Top