Most coolant concentrates are made to be diluted with demineralised water. Mixing with tap water works against the coolant you paid for.
What hard water does to a cooling system
Calcium and magnesium in tap water form scale on hot surfaces, which narrows radiator tubes and engine passages and cuts heat transfer. Chlorides and other dissolved salts also use up the coolant's corrosion inhibitors faster, so the mix stops protecting the metal sooner.
Mixing it right
- Check the coolant maker's ratio. A 50/50 mix is common, but not universal.
- Mix in a clean container kept for coolant, never one that held other chemicals.
- Use demineralised water for the mix and for later top-ups.
- Label the mixed coolant with the date and ratio.
Pre-mixed or concentrate?
Pre-mixed coolant is convenient but you pay to freight the water. Workshops and fleets that go through a lot of coolant often buy concentrate and mix it on site with demineralised water from a 200 L drum or a 1,000 L IBC.
Getting demineralised water for the workshop
We supply demineralised water in 20 L drums, 200 L drums and 1,000 L IBCs, and it can come on the same delivery as your AdBlue®.
See demineralised water prices and sizes, IBC and bulk supply or the spec sheet.