Laundry Chemical Dosing: How Much to Use Per Load

Quick answer: Laundry chemical dosing is set by two numbers: the dry weight of the load and the hardness of the water. Weigh the load, read the hardness once, and take the dose from the chart that ships with each product, adjusting up one step for hard water or heavy soil. Under-dosing causes redeposition and rewashes; over-dosing causes residue, extra rinsing and wasted product. Both cost more than getting it right.

Laundry chemical dosing starts with load weight and water hardness

Every dosing chart in the trade is written in terms of chemical per kilogram of dry linen. That means the first tool in the dosing process is a weighing scale at the loading point, not a measuring jug. Fill the machine to its rated capacity by dry weight, not by how full the drum looks; a drum that looks full of towels weighs far less than the same drum full of denim.

The second number is water hardness. Calcium and magnesium in hard water bind part of the detergent before it ever touches the soil, so the same load in hard water needs a higher dose, or a water softener upstream. Test the water at the machine inlet with a hardness strip, write the result on the wall next to the dosing chart, and test again whenever the water source changes. Borewell and tanker water in many Indian cities is considerably harder than municipal supply.

Soil level is the third adjustment. Light hotel linen, everyday shirts and heavy kitchen uniforms are three different jobs. Most charts give a light, medium and heavy column; choose by the dirtiest item in the load, because the load is only clean when that item is clean. The products these charts refer to are described in the guide to laundry chemical names and uses.

Under-dosing and over-dosing both cost money

Under-dosing looks like saving. It is not. When there is too little detergent in the water, soil that has been lifted from the fabric has nothing to hold it in suspension, so it settles back onto the load. This redeposition is why under-dosed whites go grey rather than dirty. The result is a rewash, which costs a full cycle of water, power, labour and chemical on top of the first one, plus the wear of an extra wash on the linen.

Over-dosing is the more common fault and the better hidden. Once the correct dose is reached, extra detergent does not clean more. It stays in the fabric as residue, which makes towels stiff and scratchy, causes guest and customer skin complaints, dulls colours, attracts soil faster between washes, and demands extra rinse cycles. Over-dosed softener coats fibres until towels stop absorbing water. Over-dosed bleach yellows polyester and shortens the life of cotton. The guide on hotel laundry chemicals covers how this shows up in a hotel's linen replacement budget.

The honest way to see the cost is to count rewashes and rinse extensions for a month. A laundry with no dosing discipline usually finds both numbers higher than it expected.

A worked example, in words

1. Weigh the load. The operator loads the washer with a mix of cotton shirts and trousers and checks the scale: the dry weight is a little under the machine's rated capacity. Good; the drum is full but not packed.
2. Read the wall. The hardness card by the machine says the inlet water tested as moderately hard last month, and the source has not changed.
3. Classify the soil. The shirts are everyday office wear with a few collar rings, so the load is medium soil. The collar rings are pre-spotted by hand at the sorting table before loading, as described in the guide on removing sweat stains from shirt collars.
4. Take the dose from the chart. The operator follows the dosing chart that ships with each product: main-wash detergent at the medium-soil rate for that weight, stepped up one column for moderately hard water. Softener goes in the final rinse at the rate on its own chart. No bleach, because the load is coloured.
5. Measure, do not pour. The dose is measured with the marked jug or the dosing pump, never estimated from the drum.
6. Check the result. At unloading, the operator looks for grey tide marks (under-dose), a slippery feel or foam in the final rinse (over-dose), and records the load.

The point of the example is that no step involved guessing a figure. The chart gives the figure; the operator only supplies weight, hardness and soil level.

Diluting spotters

Spotting chemicals are concentrated and most are diluted before they reach the board. A spotter used neat where the chart calls for dilution does not remove the stain faster; it removes dye and weakens fibre. Each Purolix spotter ships with its own dilution guidance, so the method is simple: make up the diluted working bottle from the concentrate, label it with the product name, the dilution and the date, and never top up a working bottle with concentrate. Make a fresh bottle when it runs out. How the six spotters are used in sequence is covered in the guide to the stain removers dry cleaners actually use, and the full set is on the spotting system page.

Record keeping

A dosing record is one sheet per machine with a line per load: date, operator, load type, dry weight, soil level, products used and the dose of each, and a one-word result. It takes thirty seconds per load and gives you three things. It shows which operator is over-dosing without anyone having to say so. It lets you reconcile chemical consumption against loads washed at month end, which is the only honest check on whether product is being wasted or walking out of the store. And it gives Purolix support something to work from when a result is wrong; a photo of the sheet usually answers the question faster than a phone call.

Stocking the shelf

Good dosing does not need special products, only the chart, a scale and a measuring jug. Where it does change your shelf is in pack size: a laundry that doses correctly buys less, and can plan reorders from the record sheet instead of from an empty drum. Every product on the Purolix Wash and Rinse page ships with its dosing chart, with prices published per litre, GST extra. If you want help translating your machine capacity and water test into a starting dose, send both through the contact page and we will reply with a chart marked up for your store.