Placing cable in a conduit containing trapped water

Running a pull-string through a conduit containing trapped water can be challenging. If you know in advance that water is present, you can blow both the pull-string and the water through the conduit. Another alternative is to run a long fish tape through the conduit--or run fish tapes from each end, hoping you can hook them up in the middle. However, if you do not have the proper equipment to implement these solutions, you may have to resort to items from the local hardware store.

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Bob Jensen and Scott Morgan,

FOT Datacom

Problem

Running a pull-string through a conduit containing trapped water can be challenging. If you know in advance that water is present, you can blow both the pull-string and the water through the conduit. Another alternative is to run a long fish tape through the conduit--or run fish tapes from each end, hoping you can hook them up in the middle. However, if you do not have the proper equipment to implement these solutions, you may have to resort to items from the local hardware store.

Solution

You can do the job with a shop vacuum cleaner, pull-string, plastic bag and a garden hose or two, depending on the length of the conduit. The shop vac can be attached to the garden hose to remove the trapped water from the conduit. The plastic bag can then be attached to the pull-string to form a parachute, and with the shop vac you can blow the parachute through the conduit. Longer runs may require a second shop vac to provide suction at the other end.

Procedure

1) Blow the pull-string into the conduit from either end to locate the trapped water.

2) Extend the garden hose through the conduit and into the trapped water.

3) Use the shop vac attached to the garden hose to remove the water.

4) Tie the pull-string onto the plastic bag to form a parachute, leaving enough slack in the string to extend through the conduit and out the other end.

5) Place the parachute and the slack pull-string into the end of the conduit. Secure the free end of the pull-string to prevent it from disappearing into the conduit.

6) Attach the shop-vac hose to the conduit and blow the parachute through it.

7) Attach a pull-rope to the pull-string. Once the pull-rope has been pulled through the conduit, attach the cable to it and pull it through.

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Click here to enlarge image

A garden hose and shop vacuum can be used to remove trapped water from a conduit; the vacuum can then be used to blow a parachute through the conduit.

Bob Jensen is operations manager and Scott Morgan is a project manager at FOT Datacom, Austin, TX.

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