Just boiling water, so should be okay, right?
There will be some corrosion issues, how fast and how bad will depend
on what the water chemistry is like. Tap water is not pure water and
has dissolved minerals in it. These minerals make it conductive and a
silver / copper / stainless battery will be set up if the stainless
is fully passivated then there will be minimal stainless corrosion
but if the passivation layer is damaged there will be corrosion.
Silver is the most noble of the metals in the mix so the copper will
also corrode, but because the silver will likely have the smallest
surface area exposed to the liquid there will likely be minimal
effect from it but, looking around the braze joint for evidence of
corrosion might not be a bad idea.
James Binnion Metal Arts