Navien Heating Box questions

klaus

I have Navien tankless water heater in combination with their Heating Box. It's less than a year old but our city water is quite hard (24 grains) and would like to clean it internally soon. Have you heard of TerraSol for cleaning these appliances? Is there any advantage to using this over a water and vinegar mixture? EMCO wants $30CDN /L for the TerraSol.

Also, the Heating Boxes have 2 pumps that create quite a bit of noise. They are Armstrong pumps. I wasn't sure if they were working right. I spoke indirectly to an Armstrong rep and it turns out that yes, the pumps installed in Heating Boxes *are* loud. Navien engineers replaced one pump with another brand (they said it was from a Navien-owned company) and it is much quieter, more along the lines of what i expected. So my question is, are these pumps designed specifically for this purpose? Is there any danger in changing them our to other brands? Are the Armstrongs any more durable than other brands?