diff --git a/src/pyEQL/engines.py b/src/pyEQL/engines.py
index 9ba9c338..d62b1ebb 100644
--- a/src/pyEQL/engines.py
+++ b/src/pyEQL/engines.py
@@ -761,7 +761,7 @@ def equilibrate(
         # tolerance (in moles) for detecting cases where an element amount
         # is no longer balanced because of species that are not recognized
         # by PHREEQC.
-        _atol = 1e-16
+        _rtol = 0.05  # differing by more than 5%
 
         new_el_dict = solution.get_el_amt_dict(nested=True)
         for el in orig_el_dict:
@@ -770,7 +770,8 @@ def equilibrate(
 
             # If this element went "missing", add back all components that
             # contain this element (for any valence value)
-            if orig_el_amount - new_el_amount > _atol:
+            # if orig_el_amount - new_el_amount > _atol:
+            if new_el_amount == 0 and orig_el_amount > 0:
                 logger.info(
                     f"PHREEQC discarded element {el} during equilibration. Adding all components for this element."
                 )
@@ -782,6 +783,12 @@ def equilibrate(
                         if component not in solution.components
                     }
                 )
+            elif abs(orig_el_amount - new_el_amount) / orig_el_amount > _rtol:
+                logger.warning(
+                    f"PHREEQC returned a total Element {el} concentration of {new_el_amount} mol, "
+                    f"which differs from the original concentration of {orig_el_amount}. This "
+                    "should never occur and indicates an error in the PHREEQC database or calculation."
+                )
 
         # re-adjust charge balance for any missing species
         # note that if balance_charge is set, it will have been passed to PHREEQC, so the only reason to re-adjust charge balance here is to account for any missing species.