Quick Answer

Plumbers most often use core bits from 1-1/8" (28mm) up to 4" (100mm) for pipe and drain holes, while electricians typically use 1-1/8" (28mm) to 2" (50mm) bits for conduit. For holes through reinforced concrete, use a wet diamond core bit; for hollow block or brick, a dry core bit works. Always size the hole 5-10mm larger than the pipe or conduit so you can seal around it properly.

What Diameter Core Bits Do Plumbers Use Most?

• 28mm (1-1/8") — hot and cold water pipes, small conduits.
• 50mm (2") — soil vent pipes, larger electrical conduits.
• 100mm (4") — waste and drainage pipes, multi-duct runs.

If you run several conduits side by side, drill a single larger opening and install a grommet plate rather than drilling many small holes.

Wet or Dry Bit for Plumbing and Electrical Work?

Job Condition	Recommended Bit	Why
Reinforced concrete, indoors with water access	Wet diamond core bit	Fast, clean cut, longer life
Brick, block, lightweight walls	Dry core bit	No water cleanup, interval drilling
Tile before drilling the wall behind	Dry core bit, start slow	Avoids cracking the glaze

How to Use a Core Bit for Pipe Holes

• Mark the centre and use a pilot or starter guide to stop wandering.
• Drill at a 90° angle — use a level on the machine body.
• Keep a steady feed pressure; let the diamond segments do the cutting.
• For wet drilling, keep water flowing to the crown at all times.
• Break out the core cleanly with a chisel if it does not release on its own.

Safety Tips

• Anchor the drill with a base plate or vacuum pad to prevent kickback.
• Wear eye protection and a dust mask — silica dust is hazardous.
• Use a dust collector adapter when dry drilling indoors.
• Never force a binding bit; stop and check the pilot.

Frequently Asked Questions

Q: Can I drill through a pipe accidentally hidden in the wall?

A: Use a stud finder and check both sides of the wall first. Core drilling cuts through metal slowly and damages the bit, so verify the drilling path before starting.

Q: Do I need a special bit for concrete block?

A: No — a dry core bit handles brick and block well. For dense reinforced concrete, switch to a wet bit for speed and life. Browse our diamond core drill bits range for both options.

Q: How big should the hole be around a 32mm pipe?

A: Drill 40-45mm to leave room for the sealant and pipe movement. Check your local plumbing code for the required clearance.

Conclusion

Match the core bit diameter to your pipe or conduit, choose wet for reinforced concrete and dry for block and brick, and control the angle and feed rate for a clean hole every time. For professional-grade wet and dry bits in 28-100mm diameters, contact JOY TECH for bulk and OEM supply.