heating system I installed in my home 10/14. 120 year old house underwent a gut renovation. I used a +/-25% propylene glycol mixture for freeze/ rust inhibitor in secondary loop. Governale cast iron baseboard and radiators. I spoke with Rinnai reps at a trade show and they were skeptical that this would work in the application. I have had no issues and it has worked great since install.

Rinnai tankless hot water heater, Taco x pump block, Uponor manifold, Taco mixing valve