Detergents in the UK come with very specific dose amounts. This is because water hardness varies all over the United Kingdom.
In the UK detergent is dosed by metric volume- in millilitres (mL) to ensure accurate dosage each time, and maintain dosing consistency. Any appropriate container with mL measurements can be used (eg a measuring jug or even an unused baby bottle). Both Unilever and Proctor & Gamble send out free dosing devices on request.
For more information on what is in detergents and the function of the raw materials see our information on Mainstream Detergents, Fragrance in Detergent, Enzymes, Optical Brighteners and Plant based, Sensitive & “Eco” Detergents, and the WashWise information sheet on Laundry Detergent Ingredients.
Dosing accurately relies on three things:
- Amount of soiling (light, medium or heavy)
- Water hardness (soft, moderate or hard)
- Drum size
To calculate how much detergent needed for both pre-wash and main wash it’s easiest to work out the total amount needed for the main wash. Once this amount is calculated, the pre-wash amount will be exactly half required for the main wash.
How To Calculate The Detergent Amount Needed For a Main Wash
PLEASE NOTE: the dosages in the graphics below are specific to the detergent used in this example. Please check your detergent label carefully.
Turn to the dose instructions on the side/back of the detergent label (both powders and liquids).
1. Establish the water quality (ie hardness).
Water hardness varies all over the United Kingdom. The majority of people will know the water hardness, especially if living in a hard water area, due to the limescale build-up that is visible. If unsure, visit your local water authority’s website.
2. Always treat nappies as heavily soiled laundry.
Nappies are very dirty laundry, for this reason, always refer to the appropriate dosing for heavy soiling.
3. Find the appropriate amount for heavy soiling in relation to water hardness.
Follow the guide for the heavily soiling column for the appropriate water hardness, see the corresponding dose.
In this example, the amount needed to wash nappies in hard water is 190 ml
4. Add the additional amount specified for larger machines.
All mainstream detergents will recommend adding extra detergent for machines larger than 5kg. This will be specified somewhere on the pack.
In this example, if you are washing nappies in an 8 kg machine in a hard water area, you would add an additional 40ml to the 190ml specified. This means a total of 230ml will be used for the main wash.
If the machine is very large, 10kg or bigger, add twice the additional amount.
How To Calculate The Detergent Amount Needed For a Prewash
Divide the dose amount for the main wash BY HALF. Eg. If the main wash needs 230 ml, a pre-wash will require 115 ml.
No two brands are the same, quality can vary. If nappies don’t appear to be cleaning very well (and other troubleshooting methods have been ruled out), consider increasing/ decreasing dosage, do this in 30-40 ml increments.