New Tarm Solo Innova 30

You're right. But what concerns me is that the copper coils would be happier with a PH sightly lower than 8 - 10.

Well, my brothers is nearly identical and gone for 10 years so far. Should probably check it out, but there's Ben no problems. Mine's easy enough to drain and get into, I'll be keeping an eye on it.

This isn't a significant issue. Copper is adversely affected with pH below 7.0 (acidic). Copper dissolves in acidic solutions, and blue/green stain is evidence of this. Copper pitting can occur in high pH water with low dissolved inorganic carbon and in the presence of chloride. While ideal pH for copper is 7-8, the ideal pH for steel is in the 8-9 level (and can be higher) to prevent steel corrosion, which is the major problem with steel boiler systems. 8.8 to 9.2 pH might be the best compromise for both. Water treatments are available for both steel and copper which address these problems, thus my statement of 8-10 pH. Also, the relatively low temperature of water in a home boiler system (much less than 400F) results in minimal impacts on copper. For more info than you might want to know, take a look at this article.

http://www.gewater.com/handbook/boiler_water_systems/ch_11_preboiler.jsp