I discovered a small leak in the old RV-style water system, just under the shower faucets in the master head (bathroom). A water leak is no good anywhere, but it is particularly problematic on a boat!
After poking around for a while, I isolated the leak at this old t-fitting.
Rather than try to replace the fitting with the same old RV-style plumbing, I upgraded that portion to PEX tubing and fittings. The new stuff is color-coded, too!