diff --git a/ReleaseNotes2_3.md b/ReleaseNotes2_3.md
index 059b0d6..11f39d7 100644
--- a/ReleaseNotes2_3.md
+++ b/ReleaseNotes2_3.md
@@ -42,6 +42,8 @@ This document describes the changes and updates that have been made in version 2
 
  - `EN_PRESS_UNITS` can now be used with `EN_getoption` and `EN_setoption` to get or set the pressure unit used in EPANET.
 
+ - Decoupled pressure units from the flow unit system, allowing them to be set independently to support mixed-unit conventions (e.g., using LPS for flow and PSI for pressure).
+
  - The following constants can be used with EN_getnodevalue to retrieve the components of a node's total demand at a given point in time:
    - `EN_FULLDEMAND` - the consumer demand requested
    - `EN_DEMANDFLOW` - the consumer demand delivered
diff --git a/src/epanet.c b/src/epanet.c
index b872751..97603f9 100644
--- a/src/epanet.c
+++ b/src/epanet.c
@@ -1411,8 +1411,6 @@ int DLLEXPORT EN_setoption(EN_Project p, int option, double value)
     case EN_PRESS_UNITS:
         unit = ROUND(value);
         if (unit < 0 || unit > METERS) return 205;
-        if (p->parser.Unitsflag == US && unit > PSI) return 0;
-        if (p->parser.Unitsflag == SI && unit == PSI) return 0;
         p->parser.Pressflag = unit;
 
         dfactor = Ucf[DEMAND];
diff --git a/src/input1.c b/src/input1.c
index ad15dba..f187ea5 100644
--- a/src/input1.c
+++ b/src/input1.c
@@ -103,7 +103,7 @@ void setdefaults(Project *pr)
     pr->Warnflag = FALSE;       // Warning flag is off
     parser->Unitsflag = US;     // US unit system
     parser->Flowflag = GPM;     // Flow units are gpm
-    parser->Pressflag = PSI;    // Pressure units are psi
+    parser->Pressflag = UNITDEFAULT; // Pressure units set based on unit system
     out->Hydflag = SCRATCH;     // No external hydraulics file
     rpt->Tstatflag = SERIES;    // Generate time series output
 
@@ -269,8 +269,11 @@ void adjustdata(Project *pr)
     }
 
     // Revise pressure units depending on flow units
-    if (parser->Unitsflag != SI) parser->Pressflag = PSI;
-    else if (parser->Pressflag == PSI) parser->Pressflag = METERS;
+    if (parser->Pressflag == UNITDEFAULT)
+    {
+        if (parser->Unitsflag == SI) parser->Pressflag = METERS;
+        else parser->Pressflag = PSI;
+    }
     
     // Store value of viscosity & diffusivity
     ucf = 1.0;
@@ -404,8 +407,6 @@ void initunits(Project *pr)
         strcpy(rpt->Field[DEMAND].Units, RptFlowUnitsTxt[parser->Flowflag]);
         strcpy(rpt->Field[ELEV].Units, u_METERS);
         strcpy(rpt->Field[HEAD].Units, u_METERS);
-        if (parser->Pressflag == METERS) strcpy(rpt->Field[PRESSURE].Units, u_METERS);
-        else                             strcpy(rpt->Field[PRESSURE].Units, u_KPA);
         strcpy(rpt->Field[LENGTH].Units, u_METERS);
         strcpy(rpt->Field[DIAM].Units, u_MMETERS);
         strcpy(rpt->Field[FLOW].Units, RptFlowUnitsTxt[parser->Flowflag]);
@@ -423,8 +424,6 @@ void initunits(Project *pr)
         if (parser->Flowflag == CMS) qcf = CMSperCFS;
 
         hcf = MperFT;
-        if (parser->Pressflag == METERS) pcf = MperFT * hyd->SpGrav;
-        else pcf = KPAperPSI * PSIperFT * hyd->SpGrav;
         wcf = KWperHP;
     }
     else  // US units
@@ -448,10 +447,17 @@ void initunits(Project *pr)
         if (parser->Flowflag == IMGD) qcf = IMGDperCFS;
         if (parser->Flowflag == AFD)  qcf = AFDperCFS;
         hcf = 1.0;
-        pcf = PSIperFT * hyd->SpGrav;
         wcf = 1.0;
     }
 
+    if (parser->Pressflag == METERS)   strcpy(rpt->Field[PRESSURE].Units, u_METERS);
+    else if (parser->Pressflag == KPA) strcpy(rpt->Field[PRESSURE].Units, u_KPA);
+    else                               strcpy(rpt->Field[PRESSURE].Units, u_PSI);
+
+    if (parser->Pressflag == METERS) pcf = MperFT * hyd->SpGrav;
+    else if (parser->Pressflag == KPA) pcf = KPAperPSI * PSIperFT * hyd->SpGrav;
+    else pcf = PSIperFT * hyd->SpGrav;
+
     strcpy(rpt->Field[QUALITY].Units, "");
     ccf = 1.0;
     if (qual->Qualflag == CHEM)
diff --git a/src/types.h b/src/types.h
index 2bd2629..b48f84e 100755
--- a/src/types.h
+++ b/src/types.h
@@ -238,7 +238,8 @@ typedef enum {
 typedef enum {
   PSI,           // pounds per square inch
   KPA,           // kiloPascals
-  METERS         // meters
+  METERS,        // meters
+  UNITDEFAULT    // default based on unit system (SI or US)
 } PressureUnitsType;
 
 typedef enum {
diff --git a/tests/test_units.cpp b/tests/test_units.cpp
index 8397af9..53d8c5f 100644
--- a/tests/test_units.cpp
+++ b/tests/test_units.cpp
@@ -74,13 +74,13 @@ BOOST_FIXTURE_TEST_CASE(test_pressure_units, FixtureInitClose)
     BOOST_REQUIRE(error == 0);
     BOOST_CHECK(units == EN_PSI);
 
-    // Change to pressure from PSI to meters and check it's still PSI
+    // Change to pressure from PSI to meters and check it is meters
     error = EN_setoption(ph, EN_PRESS_UNITS, EN_METERS);
     BOOST_REQUIRE(error == 0);
 
     error = EN_getoption(ph, EN_PRESS_UNITS, &units);
     BOOST_REQUIRE(error == 0);
-    BOOST_CHECK(units == EN_PSI);
+    BOOST_CHECK(units == EN_METERS);
 
     // Change flow units to LPS to change to metric units and rerun simulation
     error = EN_setflowunits(ph, EN_LPS);
@@ -108,12 +108,12 @@ BOOST_FIXTURE_TEST_CASE(test_pressure_units, FixtureInitClose)
     BOOST_REQUIRE(error == 0);
     BOOST_CHECK(abs(p - 298.76035) < 1.e-5);
 
-    // Set pressure to PSI and check that it remains in kPa
+    // Set pressure to PSI and check that it has changed to PSI
     error = EN_setoption(ph, EN_PRESS_UNITS, EN_PSI);
     BOOST_REQUIRE(error == 0);
     error = EN_getoption(ph, EN_PRESS_UNITS, &units);
     BOOST_REQUIRE(error == 0);
-    BOOST_CHECK(units == EN_KPA);
+    BOOST_CHECK(units == EN_PSI);
 
     error = EN_closeH(ph);
     BOOST_REQUIRE(error == 0);
@@ -264,4 +264,197 @@ BOOST_FIXTURE_TEST_CASE(test_rule_unit_change,  FixtureOpenClose)
 
 }
 
+BOOST_FIXTURE_TEST_CASE(test_decoupled_pressure_units, FixtureInitClose)
+{
+    int index;
+    long t;
+    double p, units;
+
+    // Create basic network
+    error = EN_addnode(ph, "R1", EN_RESERVOIR, &index);
+    BOOST_REQUIRE(error == 0);
+    error = EN_setnodevalue(ph, index, EN_ELEVATION, 100);
+    BOOST_REQUIRE(error == 0);
+    error = EN_addnode(ph, "J1", EN_JUNCTION, &index);
+    BOOST_REQUIRE(error == 0);
+    error = EN_addlink(ph, "P1", EN_PIPE, "R1", "J1", &index);
+    BOOST_REQUIRE(error == 0);
+
+    // Test 1: Start with US flow units (GPM) and change to PSI
+    error = EN_setflowunits(ph, EN_GPM);
+    BOOST_REQUIRE(error == 0);
+
+    // Should succeed in setting PSI pressure units
+    error = EN_setoption(ph, EN_PRESS_UNITS, EN_PSI);
+    BOOST_REQUIRE(error == 0);
+
+    error = EN_getoption(ph, EN_PRESS_UNITS, &units);
+    BOOST_REQUIRE(error == 0);
+    BOOST_CHECK(units == EN_PSI);
+
+    // Test 2: With US flow units, set pressure to meters (should now work)
+    error = EN_setoption(ph, EN_PRESS_UNITS, EN_METERS);
+    BOOST_REQUIRE(error == 0);
+
+    error = EN_getoption(ph, EN_PRESS_UNITS, &units);
+    BOOST_REQUIRE(error == 0);
+    BOOST_CHECK(units == EN_METERS);
+
+    // Test 3: With US flow units, set pressure to kPa (should now work)
+    error = EN_setoption(ph, EN_PRESS_UNITS, EN_KPA);
+    BOOST_REQUIRE(error == 0);
+
+    error = EN_getoption(ph, EN_PRESS_UNITS, &units);
+    BOOST_REQUIRE(error == 0);
+    BOOST_CHECK(units == EN_KPA);
+
+    // Test 4: Change to SI flow units (LPS) but keep kPa pressure
+    error = EN_setflowunits(ph, EN_LPS);
+    BOOST_REQUIRE(error == 0);
+
+    // Pressure units should remain kPa (not auto-changed to meters)
+    error = EN_getoption(ph, EN_PRESS_UNITS, &units);
+    BOOST_REQUIRE(error == 0);
+    BOOST_CHECK(units == EN_KPA);
+
+    // Test 5: With SI flow units, set pressure to PSI (should now work)
+    error = EN_setoption(ph, EN_PRESS_UNITS, EN_PSI);
+    BOOST_REQUIRE(error == 0);
+
+    error = EN_getoption(ph, EN_PRESS_UNITS, &units);
+    BOOST_REQUIRE(error == 0);
+    BOOST_CHECK(units == EN_PSI);
+
+    // Test 6: Run simulation and check pressure values are correctly converted
+    error = EN_openH(ph);
+    BOOST_REQUIRE(error == 0);
+    error = EN_initH(ph, EN_NOSAVE);
+    BOOST_REQUIRE(error == 0);
+    error = EN_runH(ph, &t);
+    BOOST_REQUIRE(error == 0);
+
+    // Get pressure in PSI (should be ~43.33 PSI for 100 ft head)
+    error = EN_getnodevalue(ph, 1, EN_PRESSURE, &p);
+    BOOST_REQUIRE(error == 0);
+    BOOST_CHECK(abs(p - 43.33) < 1.e-5);
+
+    // Change pressure units to meters during simulation
+    error = EN_setoption(ph, EN_PRESS_UNITS, EN_METERS);
+    BOOST_REQUIRE(error == 0);
+
+    // Pressure should now be in meters (~30.48 m for 100 ft head)
+    error = EN_getnodevalue(ph, 1, EN_PRESSURE, &p);
+    BOOST_REQUIRE(error == 0);
+    BOOST_CHECK(abs(p - 30.48) < 1.e-5);
+
+    error = EN_closeH(ph);
+    BOOST_REQUIRE(error == 0);
+}
+
+BOOST_FIXTURE_TEST_CASE(test_automatic_pressure_unit_switching, FixtureInitClose)
+{
+    int index;
+    double pressure_units;
+
+    // Create basic network
+    error = EN_addnode(ph, "R1", EN_RESERVOIR, &index);
+    BOOST_REQUIRE(error == 0);
+    error = EN_setnodevalue(ph, index, EN_ELEVATION, 100);
+    BOOST_REQUIRE(error == 0);
+    error = EN_addnode(ph, "J1", EN_JUNCTION, &index);
+    BOOST_REQUIRE(error == 0);
+    error = EN_addlink(ph, "P1", EN_PIPE, "R1", "J1", &index);
+    BOOST_REQUIRE(error == 0);
+
+    // Test 1: Start with US flow units (CFS) - should have PSI pressure units
+    error = EN_setflowunits(ph, EN_CFS);
+    BOOST_REQUIRE(error == 0);
+    error = EN_getoption(ph, EN_PRESS_UNITS, &pressure_units);
+    BOOST_REQUIRE(error == 0);
+    BOOST_CHECK(pressure_units == EN_PSI);
+
+    // Test 2: Change from US flow units (CFS) to metric flow units (LPS)
+    // Pressure units should automatically change from PSI to METERS
+    error = EN_setflowunits(ph, EN_LPS);
+    BOOST_REQUIRE(error == 0);
+    error = EN_getoption(ph, EN_PRESS_UNITS, &pressure_units);
+    BOOST_REQUIRE(error == 0);
+    BOOST_CHECK(pressure_units == EN_METERS);
+
+    // Test 3: Change from metric flow units (LPS) back to US flow units (GPM)
+    // Pressure units should automatically change from METERS to PSI
+    error = EN_setflowunits(ph, EN_GPM);
+    BOOST_REQUIRE(error == 0);
+    error = EN_getoption(ph, EN_PRESS_UNITS, &pressure_units);
+    BOOST_REQUIRE(error == 0);
+    BOOST_CHECK(pressure_units == EN_PSI);
+
+    // Test 4: Change from US flow units (GPM) to another metric flow unit (MLD)
+    // Pressure units should automatically change from PSI to METERS
+    error = EN_setflowunits(ph, EN_MLD);
+    BOOST_REQUIRE(error == 0);
+    error = EN_getoption(ph, EN_PRESS_UNITS, &pressure_units);
+    BOOST_REQUIRE(error == 0);
+    BOOST_CHECK(pressure_units == EN_METERS);
+
+    // Test 5: Manually set pressure units to kPa while using metric flow units
+    error = EN_setoption(ph, EN_PRESS_UNITS, EN_KPA);
+    BOOST_REQUIRE(error == 0);
+    error = EN_getoption(ph, EN_PRESS_UNITS, &pressure_units);
+    BOOST_REQUIRE(error == 0);
+    BOOST_CHECK(pressure_units == EN_KPA);
+
+    // Test 6: Change from metric flow units (MLD) to US flow units (MGD)
+    // Pressure units should automatically change from kPa to PSI
+    error = EN_setflowunits(ph, EN_MGD);
+    BOOST_REQUIRE(error == 0);
+    error = EN_getoption(ph, EN_PRESS_UNITS, &pressure_units);
+    BOOST_REQUIRE(error == 0);
+    BOOST_CHECK(pressure_units == EN_PSI);
+
+    // Test 7: Change from US flow units (MGD) to metric flow units (CMH)
+    // Pressure units should automatically change from PSI to METERS
+    error = EN_setflowunits(ph, EN_CMH);
+    BOOST_REQUIRE(error == 0);
+    error = EN_getoption(ph, EN_PRESS_UNITS, &pressure_units);
+    BOOST_REQUIRE(error == 0);
+    BOOST_CHECK(pressure_units == EN_METERS);
+
+    // Test 8: Set pressure to kPa again with metric flow units
+    error = EN_setoption(ph, EN_PRESS_UNITS, EN_KPA);
+    BOOST_REQUIRE(error == 0);
+
+    // Test 9: Change between metric flow units (CMH to CMD)
+    // Pressure units should remain kPa (not changed to METERS since not switching from PSI)
+    error = EN_setflowunits(ph, EN_CMD);
+    BOOST_REQUIRE(error == 0);
+    error = EN_getoption(ph, EN_PRESS_UNITS, &pressure_units);
+    BOOST_REQUIRE(error == 0);
+    BOOST_CHECK(pressure_units == EN_KPA);
+
+    // Test 10: Change from metric flow units (CMD) to US flow units (AFD)
+    // Pressure units should automatically change from kPa to PSI
+    error = EN_setflowunits(ph, EN_AFD);
+    BOOST_REQUIRE(error == 0);
+    error = EN_getoption(ph, EN_PRESS_UNITS, &pressure_units);
+    BOOST_REQUIRE(error == 0);
+    BOOST_CHECK(pressure_units == EN_PSI);
+
+    // Test 11: Change between US flow units (AFD to IMGD)
+    // Pressure units should remain PSI
+    error = EN_setflowunits(ph, EN_IMGD);
+    BOOST_REQUIRE(error == 0);
+    error = EN_getoption(ph, EN_PRESS_UNITS, &pressure_units);
+    BOOST_REQUIRE(error == 0);
+    BOOST_CHECK(pressure_units == EN_PSI);
+
+    // Test 12: Final test - metric flow units (CMS) should change PSI to METERS
+    error = EN_setflowunits(ph, EN_CMS);
+    BOOST_REQUIRE(error == 0);
+    error = EN_getoption(ph, EN_PRESS_UNITS, &pressure_units);
+    BOOST_REQUIRE(error == 0);
+    BOOST_CHECK(pressure_units == EN_METERS);
+}
+
+
 BOOST_AUTO_TEST_SUITE_END()