When a truck already has treated water on board and you top it up, the two waters blend. Enter what's on the truck, what you're adding, and the free residual you want to deliver. The calculator works out the blended residual and the manual dose to add to reach your target.
How it's worked out
These steps use your numbers and change as you type. Answers that just changed flash, so you can see which steps each box affects.
mg/L means milligrams of chlorine in every litre of water. Multiply by litres and you get the milligrams in the whole load: mg/L × L = mg. Divide milligrams by litres and you're back to a residual: mg ÷ L = mg/L. Every step below is one of those two moves.
On the truck
- Use only chlorine certified for drinking water (NSF/ANSI/CAN 60), and keep it in its own marked measuring jug.
- Test the free residual of the water already on board, and of the source you're filling from.
- Add the dose early in the fill, so the incoming water mixes it through the tank. For calcium hypochlorite, dissolve it in a pail of treated water first and pour in the liquid, not the undissolved grit.
- Let it mix and sit for the contact time your plant uses, then test the free residual again before delivering.
- If the reading is low, add a top-up worked out from the new reading. If it's high, top up with more treated water or let it sit, then retest.
- Record the volumes, the dose added, and both residual readings in the truck log.
This page is for training. Deliver water at the residual your operating permit and water delivery procedures require, and confirm every load with a test.