I have a high capacity whole house humidifier.  My humidifier gets water from a tap in the household plumbing and uses electricity to boil the water and feed the steam into the central air ducts.  I (and my HVAC service company) recently discovered that scale builds up pretty fast inside the humidifier with the local water (4.9- 9.9 GPG according to my water company).

My HVAC service company has recommended installing a water softener or reverse osmosis system to combat the scale.  I’ve been trying to research the pros and cons of these systems.  I am having some difficulty finding reliable information, especially as it pertains to my main concern–scale buildup.

Having just discovered this blog and finding that your answers to questions seem more reasonable (and informed) than most other sites, I would like to get your opinion.

Answer:  You normally would not use reverse osmosis to resolve this problem – the most economical solution is to go with a traditional cation exchange water softener.  Scale (calcium and magnesium) will be removed by the water softener and the problem should be resolved.  The reason to avoid reverse osmosis in this application is that RO water is very pure – it has nothing in it – and it wants something in it.  This makes RO water very corrosive to any piping or mechanism that is not either stainless or plastic.  Most humidifier systems are supplied with water through copper tubing, and the humidifier’s internal parts may not be 100% compatible with RO water.  You can look at some of the water softener systems that we offer on our site.  With a hardness of around 10 GPG, you should be fine with a 32,000 grain capacity system for a family up to 5 or 6 people. Hope this helps!