Rich,
How ever you think of it, the 'steam' pipes are
going to be part of your antenna 'system', they
will have RF on them. Filters may 'help', but they
won't remove the RF from the pipes, and the possibility
for RFI is still going tobe there.
Especially at 100 watts, I seriously doubt if you
have to worry about 'blowing up' the boiler room. I
would be more worried about irrate neighbors...
'Doc

PS - Give it a try. If there are complaints, stop!