clock menu more-arrow no yes mobile

How to Identify and Treat Soft Water

Ask This Old House plumbing and heating expert Richard Trethewey answers an email about a shower stained green and why it may be linked to soft water


  1. Richard explains a green-stained shower is likely caused by soft water.
  2. Richard says when the pH level of the water drops below 6.5, the water becomes acidic. That means elements like iron, manganese, lead and sodium could be in the water.
  3. When the water becomes acidic, it can start to eat away at the copper pipes.
  4. To illustrate how acidity works, Richard places a copper pipe into a vinegar and sodium solution for 45 minutes. Then lets it sit for another 45 minutes. That quickly you can see a buildup of patina from oxidation.
  5. That greenish/blue oxidation can build up over time. When water flows through the pipes, it picks up that corrosion and comes out of the showerhead and into the shower itself.
  6. Richard explains to combat soft water, homeowners could get a calcite acid neutralizer tank. That uses white marble limestone to dissolve into the water and neutralize those extra elements and bring up the pH level of the water.