FHA arsenic treatment - point of use or whole house?

[Rowdy B.]

I own a property in Pinal County, Arizona which has a well with water tested at 0.028 mg/L (28 PPB) arsenic. I have just built four manufactured homes which will be sharing water from the well. I believe more than 50% of my potential buyers will use FHA financing. To the best of my knowledge, most Arizona lenders use the EPA drinking water standards requiring a maximum of 0.010 mg/L (10 PPB) arsenic. Most of the builders in the area (it's a rural area not serviced by city water, only wells) are installing "point of use" RO (Reverse Osmosis) systems (about $500 installed under the kitchen sink). From speaking with several realtors, using just a single RO system has been accepted by nearly all FHA loans originated by local lenders. However, I have heard of one case where the lender required a "whole house" arsenic treatment system, which are about $2500-$3000 installed. I thought I read an article once which stated that a "whole house" arsenic treatment was required by FHA for all water in the house, as well as any drinking water for pets or livestock. Unfortunately, I have not been able to find that definitive FHA guideline. If anyone could provide me a link to the FHA guidelines, I would certainly appreciate it.

By the way, here's probably the best article I've found on the subject:

https://www.mass.gov/info-details/arsenic-in-private-well-water-faqs#:~:text=Unless%20your%20arsenic%20level%20is,not%20evaporate%20into%20the%20air.

One notable quote from it:

"Unless your arsenic level is over 500 ppb, showering, bathing and other household uses are safe. Arsenic is not absorbed through the skin and does not evaporate into the air."