Decanting a 25 kg Bag in a Wet Sluice Room: The Case for Pre-Portioned Sachets

The bag arrives on a Monday, is opened with a knife, and is left folded over at the top because the scoop is inside and the next person will be back in ten minutes. By Wednesday the top two centimetres have gone stiff. By Friday there is a hard crust across the whole surface and the scoop comes out with a chunk attached. The sluice room is at 78 per cent relative humidity and 24 C, and nobody has done anything wrong except buy in bulk.

This article examines what actually happens to an open bag in a wet room, the real economics of bulk versus sachets, and the narrow set of circumstances where bulk is still the right purchase.

Moisture ingress is faster than most buyers assume

Powder at equilibrium with 78 per cent relative humidity will pick up 6 to 9 per cent of its own weight in water over five days if the bag is open to the room. That water is absorbed by the outer particles, which swell and fuse into agglomerates. The agglomerates do not re-disperse when dropped into urine; they sit on the bottom and swell slowly from the outside, which is exactly the failure mode that looks like a weak batch.

Measure it yourself. Weigh a 200 g sample, leave it open in the sluice for a week, and weigh it again. If the gain is above 4 per cent, the storage, not the product, is costing you money.

The hidden losses in decanting

Three losses, none of them on the invoice. Spillage during scooping runs at 1 to 3 per cent in a busy room, more when the scoop is used wet. Dust settling on surfaces is a cleaning cost and a small inhalation exposure for staff. And over-dosing from a heaped scoop against a level one can add another 15 to 20 per cent to consumption without anyone noticing.

Add those to the 6 per cent moisture gain and a 25 kg bag at 7.20 per kilo can deliver an effective 8.10 per kilo of usable powder. A sachet at 9.60 per kilo delivered has no spillage, no moisture gain and a fixed dose, which is why the sachet frequently wins on true cost even at a higher sticker price.

Where the sachet case is strongest

Any room under 60 per cent relative humidity control, any site with agency or rotating staff, any site where the dose is under 12 g, and any site with a dust sensitivity or a staff member with a known respiratory condition. In those settings the sachet is not a premium product, it is the correct engineering choice.

Four sachet sizes cover almost every need: 5 g for a 400 ml bottle, 8 g for a 650 ml bottle, 12 g for a litre, and 25 g for a 2 litre container. Order two sizes, not four, and label the tub by container rather than by weight.

Where bulk still wins

Three situations. High volume, meaning more than 30 kg a month, where the labour of opening sachets becomes the dominant cost. A sealed hopper with a auger or a dosing lid, which removes the open bag problem entirely. And industrial applications where the powder goes into a tank or a mixer rather than a bedside container, so dust and moisture are managed by the process.

Even in those cases, buy the bulk bag with a resealable liner and a rigid outer, store it on a pallet in a dry store rather than the sluice, and decant a week’s worth into a 2 kg lidded tub that lives on the trolley. That hybrid captures most of the bulk saving without the open-bag penalty.

The clause to add to the next order

Specify the moisture content at delivery, typically below 6 per cent, and the packaging format, meaning a polyethylene liner of at least 80 microns inside a woven outer with a stitched, not glued, closure. Ask for a % moisture value on the certificate of analysis, and reject anything above the agreed limit rather than accepting a credit. Wet powder that has been paid for is still wet powder.

We supply both formats from the same production batch, so a site can run sachets on the wards and bulk in the central store without a specification mismatch, and the pack options are listed at the SAP powder product pages.