Wet coring has two systems that matter more than the drill: water in and slurry out. Get either wrong and the bit overheats, the floor floods, or both.

Water supply sizing

Core size	Flow needed	Notes
25-50 mm	2-3 L/min	Garden tap with a proper hose is usually enough
50-100 mm	3-5 L/min	Use a flow valve at the rig
100-200 mm	5-8 L/min	Dedicated supply, not a shared tap
200 mm+	8-12 L/min	Tank and pump if supply is uncertain

Pressure matters less than flow. A 3 bar supply with a restricted hose delivers less water than a 1.5 bar supply with a clear line. Check at the bit, not at the tap.

Containment, wall work

1. Set a vacuum collar or slurry ring on the bit.
2. Place a catchment tray under the hole with a dam at the wall base.
3. Run the wet vacuum continuously; empty before it overflows, not after.
4. Protect the floor with sheeting and a mat over the sheet, so the sheet does not become a slip hazard.

Containment, floor work

• Core with the vacuum collar and a floor dam around the rig footprint.
• Keep a wet vacuum adjacent and running; slurry spreads faster than most crews expect.
• On finished floors, isolate the area with a temporary curb and seal the joints before starting.

Slurry disposal

Slurry is not drain-safe. It settles, hardens and blocks drains, and in many jurisdictions it is classified as trade waste. Options: settle in a tank or drum and dispose of the solids as construction waste, or use a slurry bag and dewater. Never hose it into a storm drain.

Water off at the right moment

Turn the water off 15-20 mm before the bit exits the wall. Running water as the bit breaks through washes out the edge and can flood the far side, which is exactly where the finish usually matters.

Three ways to get water to the rig

Most water problems on a coring job are supply problems dressed as cutting problems: a bit that glazes, a core that binds and a segment that wears out in half the expected life are often just starved of flow. Choose the supply before the rig is positioned.

Source	Practical flow	Best for	Fails when
Building tap with a regulated hose	6-12 l/min at 2-3 bar	Short runs, one rig, indoor work	Shared supply drops pressure when another tap opens
Tank plus pump (25-100 l)	10-20 l/min controlled	No tap nearby, upper floors, remote sites	Tank runs dry mid-hole and nobody notices
Pressure vessel or mains-fed cart	15-25 l/min	Large diameter, deep holes, multiple rigs	Refill logistics on a long shift

A 100 mm core at 300 mm depth needs roughly 15-25 litres of water, most of which returns as slurry. Sizing the supply to the hole, not to the hose, is the difference between a clean cut and a glazed crown.

Containment from the wall to the drain

• Collar dam on the wall: a putty or foam ring 40-50 mm high, with the vacuum nozzle inside it, catches everything that leaves the hole.
• Sheet and lip on the floor: poly sheeting taped at the edges with a raised lip, so a spill becomes a puddle rather than a flood.
• Wet vacuum running before the cut starts, not after the first overflow. Suction capacity should exceed the supply rate by a comfortable margin.
• Secondary tray under the rig's water fittings, because hose joints fail far more often than the dam does.
• Slurry settling: a tank or a filter bag before any drain. Never discharge to surface water or a storm drain.

The containment has to be built to survive a hose popping off at full flow. That is the failure that actually happens, and it happens at the worst possible moment: mid-cut, with the operator's hands full.

What "enough water" looks like at the crown

Judging flow by the sound of the hose is guesswork. Judge it at the crown, where the water has to do its work.

• Return flow at the collar should be continuous and slightly cloudy, not clear and intermittent. Clear return usually means the water is bypassing the cut.
• The crown should feel cool to the touch after a pull. A hot crown means insufficient flow or too much feed.
• Slurry should be thin enough to flow and thick enough to carry fines. Gritty, pasty slurry points to low flow.
• If the flow gauge or the tank level is available, log it at the start and the end of each hole. Two numbers catch a slow starvation that no sound reveals.

The shutdown sequence

Most spills happen at the end, when the cut is finished and attention has already moved on. Run water for 15-30 seconds after the bit clears the hole, let the vacuum take the last of it, then shut the water off before breaking the hose connection. Draining the line into a bucket rather than onto the floor is the difference between finishing clean and mopping a corridor at the end of the shift.

A 20-minute setup for water and containment saves an hour of cleanup, and it is the difference between a wet core and a flood.