diff --git a/src/cal_tools/calcat_interface2.py b/src/cal_tools/calcat_interface2.py
index 4a0e3ea124528bc4770efc63bc9f0ecdff618152..9e819c5bb9adc39ecf944863932f6457c6304944 100644
--- a/src/cal_tools/calcat_interface2.py
+++ b/src/cal_tools/calcat_interface2.py
@@ -215,10 +215,16 @@ def setup_client(
 _default_caldb_root = None
 
 def set_default_caldb_root(p: Path):
+    """Override the default root directory for constants in CalCat"""
     global _default_caldb_root
     _default_caldb_root = p
 
-def _get_default_caldb_root():
+def get_default_caldb_root():
+    """Get the root directory for constants in CalCat.
+
+    The default location is different on Maxwell & ONC; this checks which one
+    exists. Calling ``set_default_caldb_root()`` overrides this.
+    """
     global _default_caldb_root
     if _default_caldb_root is None:
         onc_path = Path("/common/cal/caldb_store")
@@ -265,7 +271,7 @@ class SingleConstant:
         if caldb_root is not None:
             caldb_root = Path(caldb_root)
         else:
-            caldb_root = _get_default_caldb_root()
+            caldb_root = get_default_caldb_root()
         return caldb_root / self.path
 
     def dataset_obj(self, caldb_root=None) -> h5py.Dataset:
diff --git a/src/cal_tools/constants.py b/src/cal_tools/constants.py
index cd4abb00f819ef75f2da7b3315adaf4f863bd3c6..21b047c003b5c8c0541479e2b75aeefc9c3f85e3 100644
--- a/src/cal_tools/constants.py
+++ b/src/cal_tools/constants.py
@@ -11,7 +11,7 @@ import numpy as np
 import h5py
 
 from calibration_client import CalibrationClient
-from cal_tools.calcat_interface2 import _get_default_caldb_root, get_client
+from cal_tools.calcat_interface2 import get_default_caldb_root, get_client
 from cal_tools.tools import run_prop_seq_from_path
 from cal_tools.restful_config import calibration_client
 
@@ -187,7 +187,7 @@ def inject_ccv(const_src, ccv_root, report_to=None):
             'file_path': str(report_path)
         }
 
-    const_dest = _get_default_caldb_root() / const_rel_path / const_filename
+    const_dest = get_default_caldb_root() / const_rel_path / const_filename
     const_dest.parent.mkdir(parents=True, exist_ok=True)
     copyfile(const_src, const_dest)