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Sondex Q&A

Question: How do you install Sondex pipe with inclinometer casing?

Answer: You will need Sondex pipe (corrugated plastic pipe used for drains), Sondex pipe couplings, Sondex sensing rings, Strong cable ties (16 inches or longer) or wire, mastic tape, and vinyl tape. The Sondex couplings are used to join lengths of Sondex pipe. The cable ties or wire are used to secure the Sondex pipe to the bottom of the casing and to hold the Sondex couplings onto the Sondex pipe. The mastic tape an vinyl tape are used to seal the bottom and each coupling so that grout cannot enter in the void between the Sondex pipe and the inclinometer casing. You should also consider installing a grout pipe (or hose) along with the casing and Sondex pipe, since it can be difficult to work a grout pipe between the Sondex pipe and the borehole wall.

  1. Cut an 8 foot section of Sondex pipe. This will be attached to the bottom section of inclinometer casing. Cut the remaining Sondex pipe into 10 foot sections.
  2. Attach sensing rings to the Sondex pipe at specified intervals. Protect the rings from corrosion with mastic and tape.
  3. Prepare the bottom section of casing as usual, then secure the bottom 12 to 18 inches of the 8 foot section of Sondex pipe to the bottom of the casing. This can be difficult because (1) the Sondex pipe is quite strong and larger in diameter than the casing, and (2) the bottom of the Sondex pipe must be sealed against entry of grout. Some people seal the bottom of the Sondex pipe using a Sondex cap, mastic and tape. Then they rivet the Sondex pipe to one side of the casing, and waterproof the rivet holes. Other people do not use the Sondex cap. They slit the bottom of the Sondex pipe to flatten it against the pipe, secure it to the casing with cable ties or wire, and then carefully waterproof it.
  4. Lower the first section into the borehole so you can connect the next section. If the borehole is full of water, you must fill the casing and Sondex pipe with water to counter buoyancy.
  5. Slide a 10 foot length of Sondex pipe over a 10 foot length of casing. Join the casing, then joint the Sondex pipe. Fit the Sondex coupling onto the butted ends of Sondex pipe. Secure with cable ties and then waterproof the entire coupling.
  6. Lower the pipe into the borehole so you can connect the next section. Join the casing, then join the Sondex pipe. Continue until the casing has reached the specified depth.
  7. Protect the top of the casing and Sondex pipe from grout spills,
  8. Backfill the borehole with grout. We recommend using our inclinometer grout mix.

Question: What is a Sondex coupling?

Answer: A Sondex coupling is a short section of drain pipe that is made to link two lengths of Sondex pipe together. The couplings are also corrugated pipe, but their corrugations are spaced so that they key into the Sondex pipe corrugations. They fit tightly and are easy to waterproof. Slope Indicator's part number is 50801601.

Question: Can I make couplings?

Answer: Yes, if you have no other choice. But first check if you can buy the couplings at local stores that sell drain pipe. They are commonly used by builders who have to install drain pipes.

If you must make couplings, cut some 8 to 12 inch lengths of Sondex pipe and slit them. To use, but the two lengths of Sondex pipe together, then fit the coupling onto the joint. Use cable ties to secure the coupling. Then use mastic and tape to waterproof the joint.



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