I have a 25 year old passive solar hot water system that still works
fine, but the pressure in the transfer fluid is low. The person who
installed the system is long out of business and there is no one in
the area to consult. I looked into pumping more Syltherm into the
system and the stuff costs $50/5gal. Yikes! Is there any reason I
can't drain the Syltherm out and replace it with Noburst or other
propylene glycol based fluid?