diff --git a/MaterialLib/Fluid/Density/IdealGasLaw.h b/MaterialLib/Fluid/Density/IdealGasLaw.h
index 466767e3288bbe9a3fa14b0429f66ceaa8f0970b..6a22e8a3c0713db56b2afe8ad7f15cb9899ab49b 100644
--- a/MaterialLib/Fluid/Density/IdealGasLaw.h
+++ b/MaterialLib/Fluid/Density/IdealGasLaw.h
@@ -43,7 +43,7 @@ public:
     double getValue(const ArrayType& var_vals) const override
     {
         return _molar_mass *
-               var_vals[static_cast<int>(PropertyVariableType::pg)] /
+               var_vals[static_cast<int>(PropertyVariableType::p)] /
                (PhysicalConstant::IdealGasConstant *
                 var_vals[static_cast<int>(PropertyVariableType::T)]);
     }
@@ -57,12 +57,12 @@ public:
                      const PropertyVariableType var) const override
     {
         const double T = var_vals[static_cast<int>(PropertyVariableType::T)];
-        const double p = var_vals[static_cast<int>(PropertyVariableType::pg)];
+        const double p = var_vals[static_cast<int>(PropertyVariableType::p)];
         switch (var)
         {
             case PropertyVariableType::T:
                 return dIdealGasLaw_dT(T, p);
-            case PropertyVariableType::pg:
+            case PropertyVariableType::p:
                 return dIdealGasLaw_dp(T, p);
             default:
                 return 0.;
diff --git a/MaterialLib/Fluid/Density/LiquidDensity.h b/MaterialLib/Fluid/Density/LiquidDensity.h
index e2f37e39d57b1dae4909e5fb9e7df34603a007cf..a615111249c0910fb1699347b3bd520841e0f591 100644
--- a/MaterialLib/Fluid/Density/LiquidDensity.h
+++ b/MaterialLib/Fluid/Density/LiquidDensity.h
@@ -71,7 +71,7 @@ public:
     double getValue(const ArrayType& var_vals) const override
     {
         const double T = var_vals[static_cast<int>(PropertyVariableType::T)];
-        const double p = var_vals[static_cast<int>(PropertyVariableType::pl)];
+        const double p = var_vals[static_cast<int>(PropertyVariableType::p)];
         return _rho0 / (1. + _beta * (T - _temperature0)) /
                (1. - (p - _p0) / _bulk_modulus);
     }
@@ -85,12 +85,12 @@ public:
                      const PropertyVariableType var) const override
     {
         const double T = var_vals[static_cast<int>(PropertyVariableType::T)];
-        const double p = var_vals[static_cast<int>(PropertyVariableType::pl)];
+        const double p = var_vals[static_cast<int>(PropertyVariableType::p)];
         switch (var)
         {
             case PropertyVariableType::T:
                 return dLiquidDensity_dT(T, p);
-            case PropertyVariableType::pl:
+            case PropertyVariableType::p:
                 return dLiquidDensity_dp(T, p);
             default:
                 return 0.;
diff --git a/MaterialLib/Fluid/FluidProperty.h b/MaterialLib/Fluid/FluidProperty.h
index 7673e79b73c21403178c4525b2e6a040b542c197..fce5a89dc3e900b64e456cd28cc042e618a3bb90 100644
--- a/MaterialLib/Fluid/FluidProperty.h
+++ b/MaterialLib/Fluid/FluidProperty.h
@@ -23,10 +23,9 @@ namespace Fluid
 /// Variable that determine the property.
 enum class PropertyVariableType
 {
-    T = 0,   ///< temperature.
-    pl = 1,  ///< pressure of the liquid phase (1st phase for some cases).
-    pg = 2,  ///< pressure of the gas phase (2nd phase for some cases).
-    number_of_variables = 3  ///< Number of property variables.
+    T = 0,                   ///< temperature.
+    p = 1,                   ///< pressure.
+    number_of_variables = 2  ///< Number of property variables.
 };
 
 const unsigned PropertyVariableNumber =
diff --git a/MaterialLib/Fluid/Viscosity/LinearPressureDependentViscosity.h b/MaterialLib/Fluid/Viscosity/LinearPressureDependentViscosity.h
index 379521fdd198b50b04d8936e26d1d272a78ecd88..0ff7fbb3c8becb480e0d3202fd3eec753caa154b 100644
--- a/MaterialLib/Fluid/Viscosity/LinearPressureDependentViscosity.h
+++ b/MaterialLib/Fluid/Viscosity/LinearPressureDependentViscosity.h
@@ -60,7 +60,7 @@ public:
      */
     double getValue(const ArrayType& var_vals) const override
     {
-        const double p = var_vals[static_cast<int>(PropertyVariableType::pl)];
+        const double p = var_vals[static_cast<int>(PropertyVariableType::p)];
         return _mu0 * (1 + _gamma * (p - _p0));
     }
 
diff --git a/MaterialLib/TwoPhaseModels/TwoPhaseFlowWithPPMaterialProperties.cpp b/MaterialLib/TwoPhaseModels/TwoPhaseFlowWithPPMaterialProperties.cpp
index e9c2c6d007f0fa17be8ac104f74d876f71821b2a..839f21956e13fe092b8edaab9e3b5aa88a15c08d 100644
--- a/MaterialLib/TwoPhaseModels/TwoPhaseFlowWithPPMaterialProperties.cpp
+++ b/MaterialLib/TwoPhaseModels/TwoPhaseFlowWithPPMaterialProperties.cpp
@@ -71,7 +71,7 @@ double TwoPhaseFlowWithPPMaterialProperties::getLiquidDensity(
 {
     ArrayType vars;
     vars[static_cast<int>(MaterialLib::Fluid::PropertyVariableType::T)] = T;
-    vars[static_cast<int>(MaterialLib::Fluid::PropertyVariableType::pl)] = p;
+    vars[static_cast<int>(MaterialLib::Fluid::PropertyVariableType::p)] = p;
     return _liquid_density->getValue(vars);
 }
 
@@ -80,7 +80,7 @@ double TwoPhaseFlowWithPPMaterialProperties::getGasDensity(const double p,
 {
     ArrayType vars;
     vars[static_cast<int>(MaterialLib::Fluid::PropertyVariableType::T)] = T;
-    vars[static_cast<int>(MaterialLib::Fluid::PropertyVariableType::pg)] = p;
+    vars[static_cast<int>(MaterialLib::Fluid::PropertyVariableType::p)] = p;
     return _gas_density->getValue(vars);
 }
 
@@ -89,17 +89,17 @@ double TwoPhaseFlowWithPPMaterialProperties::getDerivGasDensity(
 {
     ArrayType vars;
     vars[static_cast<int>(MaterialLib::Fluid::PropertyVariableType::T)] = T;
-    vars[static_cast<int>(MaterialLib::Fluid::PropertyVariableType::pg)] = p;
+    vars[static_cast<int>(MaterialLib::Fluid::PropertyVariableType::p)] = p;
 
     return _gas_density->getdValue(
-        vars, MaterialLib::Fluid::PropertyVariableType::pg);
+        vars, MaterialLib::Fluid::PropertyVariableType::p);
 }
 double TwoPhaseFlowWithPPMaterialProperties::getLiquidViscosity(
     const double p, const double T) const
 {
     ArrayType vars;
     vars[static_cast<int>(MaterialLib::Fluid::PropertyVariableType::T)] = T;
-    vars[static_cast<int>(MaterialLib::Fluid::PropertyVariableType::pl)] = p;
+    vars[static_cast<int>(MaterialLib::Fluid::PropertyVariableType::p)] = p;
     return _viscosity->getValue(vars);
 }
 
@@ -108,7 +108,7 @@ double TwoPhaseFlowWithPPMaterialProperties::getGasViscosity(
 {
     ArrayType vars;
     vars[static_cast<int>(MaterialLib::Fluid::PropertyVariableType::T)] = T;
-    vars[static_cast<int>(MaterialLib::Fluid::PropertyVariableType::pg)] = p;
+    vars[static_cast<int>(MaterialLib::Fluid::PropertyVariableType::p)] = p;
     return _gas_viscosity->getValue(vars);
 }
 
diff --git a/ProcessLib/LiquidFlow/LiquidFlowMaterialProperties.cpp b/ProcessLib/LiquidFlow/LiquidFlowMaterialProperties.cpp
index 063a1cfb6cd8a11f08e883c46db9d9c092f43788..e06196ed3e82d007f8accba6ccdbbfbc82f4051e 100644
--- a/ProcessLib/LiquidFlow/LiquidFlowMaterialProperties.cpp
+++ b/ProcessLib/LiquidFlow/LiquidFlowMaterialProperties.cpp
@@ -97,7 +97,7 @@ double LiquidFlowMaterialProperties::getLiquidDensity(const double p,
 {
     ArrayType vars;
     vars[static_cast<int>(MaterialLib::Fluid::PropertyVariableType::T)] = T;
-    vars[static_cast<int>(MaterialLib::Fluid::PropertyVariableType::pl)] = p;
+    vars[static_cast<int>(MaterialLib::Fluid::PropertyVariableType::p)] = p;
     return _liquid_density->getValue(vars);
 }
 
@@ -106,7 +106,7 @@ double LiquidFlowMaterialProperties::getViscosity(const double p,
 {
     ArrayType vars;
     vars[static_cast<int>(MaterialLib::Fluid::PropertyVariableType::T)] = T;
-    vars[static_cast<int>(MaterialLib::Fluid::PropertyVariableType::pl)] = p;
+    vars[static_cast<int>(MaterialLib::Fluid::PropertyVariableType::p)] = p;
     return _viscosity->getValue(vars);
 }
 
@@ -117,9 +117,9 @@ double LiquidFlowMaterialProperties::getMassCoefficient(
 {
     ArrayType vars;
     vars[static_cast<int>(MaterialLib::Fluid::PropertyVariableType::T)] = T;
-    vars[static_cast<int>(MaterialLib::Fluid::PropertyVariableType::pl)] = p;
+    vars[static_cast<int>(MaterialLib::Fluid::PropertyVariableType::p)] = p;
     const double drho_dp = _liquid_density->getdValue(
-        vars, MaterialLib::Fluid::PropertyVariableType::pl);
+        vars, MaterialLib::Fluid::PropertyVariableType::p);
     const double rho = _liquid_density->getValue(vars);
     assert(rho > 0.);
 
diff --git a/Tests/MaterialLib/TestFluidDensity.cpp b/Tests/MaterialLib/TestFluidDensity.cpp
index 6e3db0b5dd40a62c710a5fc64071361c553ead20..392890e1555ba42e659de4d230df05ce7998faf8 100644
--- a/Tests/MaterialLib/TestFluidDensity.cpp
+++ b/Tests/MaterialLib/TestFluidDensity.cpp
@@ -65,7 +65,7 @@ TEST(Material, checkIdealGasLaw)
     const double p = 1.e+5;
     const double R = PhysicalConstant::IdealGasConstant;
     const double expected_air_dens = molar_air * p / (R * T);
-    ArrayType vars = {{290, 0, 1.e+5}};
+    ArrayType vars = {{290, 1.e+5}};
     ASSERT_NEAR(expected_air_dens, rho->getValue(vars), 1.e-10);
 
     const double expected_d_air_dens_dT = -molar_air * p / (R * T * T);
@@ -74,7 +74,7 @@ TEST(Material, checkIdealGasLaw)
 
     const double expected_d_air_dens_dp = molar_air / (R * T);
     ASSERT_NEAR(expected_d_air_dens_dp,
-                rho->getdValue(vars, Fluid::PropertyVariableType::pg), 1.e-10);
+                rho->getdValue(vars, Fluid::PropertyVariableType::p), 1.e-10);
 }
 
 TEST(Material, checkLinearTemperatureDependentDensity)
@@ -110,7 +110,7 @@ TEST(Material, checkLiquidDensity)
         "</density>";
     const auto rho = createTestFluidDensityModel(xml);
 
-    const ArrayType vars = {{273.15 + 60.0, 1.e+6, 0.}};
+    const ArrayType vars = {{273.15 + 60.0, 1.e+6}};
     const double T0 = 273.15;
     const double p0 = 1.e+5;
     const double rho0 = 999.8;
@@ -130,5 +130,5 @@ TEST(Material, checkLiquidDensity)
     // Test the derivative with respect to pressure.
     const double fac_p = 1. - (p - p0) / K;
     ASSERT_NEAR(rho0 / (1. + beta * (T - T0)) / (fac_p * fac_p * K),
-                rho->getdValue(vars, Fluid::PropertyVariableType::pl), 1.e-10);
+                rho->getdValue(vars, Fluid::PropertyVariableType::p), 1.e-10);
 }
diff --git a/Tests/MaterialLib/TestFluidViscosity.cpp b/Tests/MaterialLib/TestFluidViscosity.cpp
index 35baaeeecb260c2b6af4977df0642c72636842a6..2ad04baeac3973d2f0013c6cb25d094c730a12ee 100644
--- a/Tests/MaterialLib/TestFluidViscosity.cpp
+++ b/Tests/MaterialLib/TestFluidViscosity.cpp
@@ -86,7 +86,7 @@ TEST(Material, checkLinearPressureDependentViscosity)
     ASSERT_NEAR(1.e-3 * (1. + 1.e-6 * (vars[1] - 1.e+5)), mu->getValue(vars),
                 1.e-10);
     ASSERT_NEAR(1.e-9,
-                mu->getdValue(vars, MaterialLib::Fluid::PropertyVariableType::pl),
+                mu->getdValue(vars, MaterialLib::Fluid::PropertyVariableType::p),
                 1.e-10);
 }