Acidic Water and pH Neutralisers

Water with a pH below 7. Taumata Arowai’s guideline for drinking water is pH 7.0 to 8.5. Rainwater is usually around pH 5.6 to 6, and bore water high in carbon dioxide can be acidic too.

Rain soaks up carbon dioxide from the air, which makes it slightly acidic, about pH 5.6. Rainwater is also very soft, with almost no minerals to balance that. A new concrete tank can raise the pH for its first few months, as lime leaches out of the concrete.

The pH itself isn’t a health risk. The risk is the metal it dissolves. Acidic water can pick up copper from pipes and lead from old brass fittings, roof flashings and lead-based paint, and lead is most harmful to babies, young children and unborn babies. A water test shows whether your water has picked any up.

Copper. Water that sits in copper pipes, usually overnight, dissolves tiny amounts of it, and above about 1 mg/L it leaves blue-green stains. A dripping tap can leave them too. Staining starts below the safe limit for copper, so stains on their own don’t mean the water is unsafe, but they show your pipes are slowly dissolving, so it’s worth testing.

It’s a common cause, but not the only one. Pinholes can also come from fast-flowing water, new pipe that hasn’t formed its protective layer yet, or hard bore water high in carbon dioxide. If you’re getting pinhole leaks, we test the water to find out whether pH is the problem.

Water flows through a tank of calcite, a crushed white marble. Acidic water dissolves a little of it, which raises the pH and adds some calcium. Calcite is self-limiting, so under normal conditions it brings the water to near neutral without overshooting.

Our standard is the upflow calcite neutraliser, in a manual or fully automatic version. The manual version needs no power, but you need to backwash it every two to four weeks. The automatic version backwashes itself, so you don’t have to think about it. We’ll tell you which suits your system at the free onsite visit.

A little harder, because it adds calcium. Rainwater is very soft to begin with, so the change is rarely a problem, and we test the hardness after we install it.

We check and refill the calcite every 6 to 12 months. How fast it goes down depends on how acidic your water is and how much you use. A manual neutraliser also needs backwashing every two to four weeks; an automatic one does it itself.

Not every home does, so test first. If your water is acidic and you have copper pipes or a copper hot water cylinder, a neutraliser is worth fitting. Rheem says rainwater from plastic tanks should be brought to pH 6.5 to 7.5 for its low pressure copper cylinders, or the warranty won’t cover them.

Use only the cold tap for drinking and cooking. Taumata Arowai advises running it for at least 10 seconds first thing in the morning, and for 2 minutes if the house has been empty for more than two days. That flushes out water that has sat in the pipes, but it doesn’t fix the water, so get it tested.