A hot caustic cycle, minute by minute
Cycle 2 takes fifty-one minutes and most of it is waiting. Here is exactly what happens, what the water does afterwards, and why contact time beats pressure every single time.
- Sheet
- 68
- Revision
- 2026-10
- Scale
- 1:1
- Drawn at
- Peoria IL
People assume washing a tote is a pressure-washer job. It is a chemistry and temperature job with a pressure washer at either end, and the difference matters because pressure moves residue around while heat and contact time actually remove it.
Heel removal
The container arrives drained but never empty. We pull the remaining half-gallon to a gallon and a half out of the sump and log it against the declaration. If it does not look like what the paperwork says, the cycle stops here.
Pre-rinse, recovered water
Ambient recovered water, moderate pressure, through the top opening and out through the open valve so the valve body gets rinsed too. This is the step most operations skip and it is the reason their valves still smell.
Caustic fill
Roughly 10% of container volume of caustic solution at 180°F. Not a full fill — the point is a hot, circulating film across the whole internal surface, not a bath.
Recirculation
Twenty-two minutes of recirculation through a spinning head. This is the part that cannot be rushed. Sugar, oil and fat films come off on a time curve, and shortening it by five minutes shows up as a tacky residue three weeks later.
Drain and neutralise
Caustic drains to the recovery sump. The container gets a neutralising rinse and we read pH on the drain stream — not on a sample from a bucket, on the stream.
Final rinse
Fresh potable water, single pass, drained through the valve. For a food-grade release this is sampled and the sample goes to the lab with the lot.
Drain down and air
Cap off, valve open, inverted on the rack. A sealed damp container grows things, and a container that goes out damp will arrive smelling of exactly what it grew.
Record
Cycle type, temperature log, operator initials, pH reading, serial. Seven-year retention. A wash you cannot document is a wash that did not happen as far as the next buyer is concerned.
Where the water goes
Every drop from that cycle except the final rinse ends up in a 6,000-gallon sump under the bays. From there it goes through an oil-water separator, settles, passes a 25-micron bag filter and then a 5-micron cartridge, and comes back to do pre-rinse and detergent duty on the next container. Net fresh water consumption for a cycle 2 is about four gallons.
| Stage | Water source | Volume | Where it goes next |
|---|---|---|---|
| Heel removal | — | ~1 gal recovered | Drummed, licensed processor |
| Pre-rinse | Recovered, filtered | 22 gal | Back to the sump |
| Caustic cycle | Recovered, heated | 27 gal | Neutralised, back to the sump |
| Neutralising rinse | Recovered | 14 gal | Back to the sump |
| Final rinse | Fresh potable | 4 gal | Sump, then make-up loss |
- Caustic is neutralised and pH-verified before it enters the recovery sump, never after.
- Food-grade final rinses are single-pass potable and are never recovered back into a product-contact rinse.
- The bays and the paved yard share the same drainage. Nothing reaches the storm system.
- Filter media is our one consumable with no recycling route. It is the largest line in our residual stream and we are not proud of it.
Four residues that beat cycle 2
- Polymerised latex and cured adhesive. Nothing rinses these. They get cut out at rebottling and the bottle is granulated.
- Absorbed aromatics. Solvent exposure goes into the polyethylene wall, not onto it. No cycle recovers that bottle for product duty, which is why we will not sell a washed solvent tote as anything but Grade C.
- Mineral scale from hard-water products. Needs acid, not caustic — a different cycle and a different neutralisation.
- Anything undeclared. We will not run a cycle against a residue we cannot name, because the wash bay operator is the person standing next to it.
Rinsing on site before we collect?
Send the records with the load. Documented rinses move containers up a price band, often by more than the rinse cost you.