diff --git a/ProcessLib/HydroMechanics/HydroMechanicsProcess.cpp b/ProcessLib/HydroMechanics/HydroMechanicsProcess.cpp
index 585c0d8bba8a3e1c84a5f52b6d1a1bfcd3b74e0f..eb8078e80c549244b5d6b04298676fffbdc82f56 100644
--- a/ProcessLib/HydroMechanics/HydroMechanicsProcess.cpp
+++ b/ProcessLib/HydroMechanics/HydroMechanicsProcess.cpp
@@ -297,11 +297,9 @@ void HydroMechanicsProcess<DisplacementDim>::assembleConcreteProcess(
     std::vector<std::reference_wrapper<NumLib::LocalToGlobalIndexMap>>
         dof_table = {std::ref(*_local_to_global_index_map)};
 
-    ProcessLib::ProcessVariable const& pv = getProcessVariables(process_id)[0];
-
     GlobalExecutor::executeSelectedMemberDereferenced(
         _global_assembler, &VectorMatrixAssembler::assemble, _local_assemblers,
-        pv.getActiveElementIDs(), dof_table, t, dt, x, x_prev, process_id, M, K,
+        getActiveElementIDs(), dof_table, t, dt, x, x_prev, process_id, M, K,
         b);
 }
 
@@ -342,12 +340,10 @@ void HydroMechanicsProcess<DisplacementDim>::
         dof_tables.emplace_back(*_local_to_global_index_map);
     }
 
-    ProcessLib::ProcessVariable const& pv = getProcessVariables(process_id)[0];
-
     GlobalExecutor::executeSelectedMemberDereferenced(
         _global_assembler, &VectorMatrixAssembler::assembleWithJacobian,
-        _local_assemblers, pv.getActiveElementIDs(), dof_tables, t, dt, x,
-        x_prev, process_id, M, K, b, Jac);
+        _local_assemblers, getActiveElementIDs(), dof_tables, t, dt, x, x_prev,
+        process_id, M, K, b, Jac);
 
     auto copyRhs = [&](int const variable_id, auto& output_vector)
     {
@@ -383,12 +379,10 @@ void HydroMechanicsProcess<DisplacementDim>::preTimestepConcreteProcess(
 
     if (hasMechanicalProcess(process_id))
     {
-        ProcessLib::ProcessVariable const& pv =
-            getProcessVariables(process_id)[0];
         GlobalExecutor::executeSelectedMemberOnDereferenced(
             &LocalAssemblerIF::preTimestep, _local_assemblers,
-            pv.getActiveElementIDs(), *_local_to_global_index_map,
-            *x[process_id], t, dt);
+            getActiveElementIDs(), *_local_to_global_index_map, *x[process_id],
+            t, dt);
     }
 }
 
@@ -412,11 +406,10 @@ void HydroMechanicsProcess<DisplacementDim>::postTimestepConcreteProcess(
         dof_tables.push_back(&getDOFTable(process_id));
     }
 
-    ProcessLib::ProcessVariable const& pv = getProcessVariables(process_id)[0];
     GlobalExecutor::executeSelectedMemberOnDereferenced(
         &LocalAssemblerIF::postTimestep, _local_assemblers,
-        pv.getActiveElementIDs(), dof_tables, x, x_prev, t, dt,
-        false /*unused*/, process_id);
+        getActiveElementIDs(), dof_tables, x, x_prev, t, dt, false /*unused*/,
+        process_id);
 }
 
 template <int DisplacementDim>
@@ -428,10 +421,9 @@ void HydroMechanicsProcess<DisplacementDim>::postNonLinearSolverConcreteProcess(
     DBUG("PostNonLinearSolver HydroMechanicsProcess.");
 
     // Calculate strain, stress or other internal variables of mechanics.
-    ProcessLib::ProcessVariable const& pv = getProcessVariables(process_id)[0];
     GlobalExecutor::executeSelectedMemberOnDereferenced(
         &LocalAssemblerIF::postNonLinearSolver, _local_assemblers,
-        pv.getActiveElementIDs(), getDOFTable(process_id), x, x_prev, t, dt,
+        getActiveElementIDs(), getDOFTable(process_id), x, x_prev, t, dt,
         false /*unused*/, process_id);
 }
 
@@ -448,10 +440,9 @@ void HydroMechanicsProcess<DisplacementDim>::
 
     DBUG("Set initial conditions of HydroMechanicsProcess.");
 
-    ProcessLib::ProcessVariable const& pv = getProcessVariables(process_id)[0];
     GlobalExecutor::executeSelectedMemberOnDereferenced(
         &LocalAssemblerIF::setInitialConditions, _local_assemblers,
-        pv.getActiveElementIDs(), getDOFTable(process_id), *x[process_id], t,
+        getActiveElementIDs(), getDOFTable(process_id), *x[process_id], t,
         _process_data.isMonolithicSchemeUsed(), process_id);
 }
 
@@ -474,10 +465,9 @@ void HydroMechanicsProcess<DisplacementDim>::computeSecondaryVariableConcrete(
         dof_tables.push_back(&getDOFTable(process_id));
     }
 
-    ProcessLib::ProcessVariable const& pv = getProcessVariables(process_id)[0];
     GlobalExecutor::executeSelectedMemberOnDereferenced(
         &LocalAssemblerIF::computeSecondaryVariable, _local_assemblers,
-        pv.getActiveElementIDs(), dof_tables, t, dt, x, x_prev, process_id);
+        getActiveElementIDs(), dof_tables, t, dt, x, x_prev, process_id);
 }
 
 template <int DisplacementDim>
diff --git a/ProcessLib/HydroMechanics/Tests.cmake b/ProcessLib/HydroMechanics/Tests.cmake
index fdbefd469a6210bf279a403de778c356ce99a6e2..6d234d2be61b16ea9b664061e5e516bb8f38d505 100644
--- a/ProcessLib/HydroMechanics/Tests.cmake
+++ b/ProcessLib/HydroMechanics/Tests.cmake
@@ -320,6 +320,21 @@ AddTest(
     output_ts_1_t_1.000000.vtu output_ts_1_t_1.000000.vtu principal_stress_values principal_stress_values 0 1e-10
 )
 
+AddTest(
+    NAME HydroMechanics_hydraulic_deactivation
+    PATH HydroMechanics/HydraulicDeactivation
+    EXECUTABLE ogs
+    EXECUTABLE_ARGS simHM_deactivate_H.prj
+    WRAPPER time
+    TESTER vtkdiff
+    REQUIREMENTS NOT OGS_USE_MPI
+    DIFF_DATA
+    hydraulic_deactivation_ts_1_t_1e+00.vtu hydraulic_deactivation_ts_1_t_1e+00.vtu pressure pressure 0 1e-12
+    hydraulic_deactivation_ts_1_t_1e+00.vtu hydraulic_deactivation_ts_1_t_1e+00.vtu displacement displacement 1e-14 0
+    hydraulic_deactivation_ts_1_t_1e+00.vtu hydraulic_deactivation_ts_1_t_1e+00.vtu sigma sigma 1e-10 0
+    hydraulic_deactivation_ts_1_t_1e+00.vtu hydraulic_deactivation_ts_1_t_1e+00.vtu epsilon epsilon 1e-14 0
+)
+
 ## Tests for Ideal gas
 # flow_no_strain
 AddTest(
diff --git a/ProcessLib/Process.cpp b/ProcessLib/Process.cpp
index 9004b0840ccfb9fbbdafe48e516c014d1fbdf8e2..e0a8ee0c38c79cc74a62dbe3d806ccdd474695c9 100644
--- a/ProcessLib/Process.cpp
+++ b/ProcessLib/Process.cpp
@@ -10,6 +10,11 @@
 
 #include "Process.h"
 
+#include <range/v3/algorithm/any_of.hpp>
+#include <range/v3/algorithm/set_algorithm.hpp>
+#include <range/v3/view/drop.hpp>
+#include <range/v3/view/transform.hpp>
+
 #include "NumLib/DOF/ComputeSparsityPattern.h"
 #include "NumLib/Extrapolation/LocalLinearLeastSquaresExtrapolator.h"
 #include "NumLib/ODESolver/ConvergenceCriterionPerComponent.h"
@@ -202,6 +207,37 @@ void Process::updateDeactivatedSubdomains(double const time,
     {
         variable.get().updateDeactivatedSubdomains(time);
     }
+
+    _ids_of_active_elements.clear();
+
+    auto active_elements_ids = ranges::views::transform(
+        [](auto const& variable)
+        { return variable.get().getActiveElementIDs(); });
+
+    // Early return if there's any process variable with all elements active.
+    if (ranges::any_of(variables_per_process | active_elements_ids,
+                       [](auto const& vector) { return vector.empty(); }))
+    {
+        return;
+    }
+
+    // Some process variable has deactivated elements. Create union of active
+    // ids.
+
+    _ids_of_active_elements =  // there is at least one process variable.
+        variables_per_process[0].get().getActiveElementIDs();
+
+    for (auto const& pv_active_element_ids :
+         variables_per_process | ranges::views::drop(1) | active_elements_ids)
+    {
+        std::vector<std::size_t> new_active_elements;
+        new_active_elements.reserve(_ids_of_active_elements.size() +
+                                    pv_active_element_ids.size());
+        ranges::set_union(_ids_of_active_elements, pv_active_element_ids,
+                          std::back_inserter(new_active_elements));
+
+        _ids_of_active_elements = std::move(new_active_elements);
+    }
 }
 
 void Process::preAssemble(const double t, double const dt,
diff --git a/ProcessLib/Process.h b/ProcessLib/Process.h
index ad90e756c2bee1902c78f059f325a44a6e6da35f..dcf6f2b0ad71f780707d4f9f7ce0c585c96e51fa 100644
--- a/ProcessLib/Process.h
+++ b/ProcessLib/Process.h
@@ -157,6 +157,11 @@ public:
         return _process_variables[process_id];
     }
 
+    std::vector<std::size_t> const& getActiveElementIDs() const
+    {
+        return _ids_of_active_elements;
+    }
+
     SecondaryVariableCollection const& getSecondaryVariables() const
     {
         return _secondary_variables;
@@ -393,6 +398,9 @@ private:
     std::vector<SourceTermCollection> _source_term_collections;
 
     ExtrapolatorData _extrapolator_data;
+
+    /// Union of active element ids per process variable
+    std::vector<std::size_t> _ids_of_active_elements;
 };
 
 }  // namespace ProcessLib
diff --git a/Tests/Data/HydroMechanics/HydraulicDeactivation/hydraulic_deactivation_ts_1_t_1e+00.vtu b/Tests/Data/HydroMechanics/HydraulicDeactivation/hydraulic_deactivation_ts_1_t_1e+00.vtu
new file mode 100644
index 0000000000000000000000000000000000000000..c5a0da9e8e9c4dccb869946239f0c8101ffcb294
--- /dev/null
+++ b/Tests/Data/HydroMechanics/HydraulicDeactivation/hydraulic_deactivation_ts_1_t_1e+00.vtu
@@ -0,0 +1,43 @@
+<?xml version="1.0"?>
+<VTKFile type="UnstructuredGrid" version="1.0" byte_order="LittleEndian" header_type="UInt64" compressor="vtkZLibDataCompressor">
+  <UnstructuredGrid>
+    <FieldData>
+      <DataArray type="Int8" Name="IntegrationPointMetaData" NumberOfTuples="166" format="appended" RangeMin="34"                   RangeMax="125"                  offset="0"                   />
+      <DataArray type="Int8" Name="OGS_VERSION" NumberOfTuples="24" format="appended" RangeMin="45"                   RangeMax="121"                  offset="176"                 />
+      <DataArray type="Float64" Name="epsilon_ip" NumberOfComponents="4" NumberOfTuples="60" format="appended" RangeMin="1.8582926052e-08"     RangeMax="0.00013530325714"     offset="264"                 />
+      <DataArray type="Float64" Name="sigma_ip" NumberOfComponents="4" NumberOfTuples="60" format="appended" RangeMin="2.9251501014"         RangeMax="21298.170979"         offset="1224"                />
+    </FieldData>
+    <Piece NumberOfPoints="32"                   NumberOfCells="15"                  >
+      <PointData>
+        <DataArray type="Float64" Name="MassFlowRate" format="appended" RangeMin="-0.00096157952648"    RangeMax="3.7773603689e-15"     offset="2344"                />
+        <DataArray type="Float64" Name="NodalForces" NumberOfComponents="2" format="appended" RangeMin="17.056813113"         RangeMax="11845.680641"         offset="2616"                />
+        <DataArray type="Float64" Name="displacement" NumberOfComponents="2" format="appended" RangeMin="0"                    RangeMax="3.9832379075e-05"     offset="3072"                />
+        <DataArray type="Float64" Name="epsilon" NumberOfComponents="4" format="appended" RangeMin="1.8582926052e-08"     RangeMax="0.0001292304"         offset="3376"                />
+        <DataArray type="UInt64" Name="original_node_number" format="appended" RangeMin="0"                    RangeMax="31"                   offset="4072"                />
+        <DataArray type="Float64" Name="pressure" format="appended" RangeMin="0"                    RangeMax="23154.828264"         offset="4204"                />
+        <DataArray type="Float64" Name="pressure_interpolated" format="appended" RangeMin="0"                    RangeMax="23154.828264"         offset="4436"                />
+        <DataArray type="Float64" Name="sigma" NumberOfComponents="4" format="appended" RangeMin="2.9251501014"         RangeMax="20342.238709"         offset="4668"                />
+      </PointData>
+      <CellData>
+        <DataArray type="Int32" Name="MaterialIDs" format="appended" RangeMin="0"                    RangeMax="4"                    offset="5572"                />
+        <DataArray type="Float64" Name="permeability" NumberOfComponents="4" format="appended" RangeMin="1.7320508076e-14"     RangeMax="1.7320508076e-14"     offset="5648"                />
+        <DataArray type="UInt8" Name="pressure_active" format="appended" RangeMin="0"                    RangeMax="1"                    offset="5732"                />
+        <DataArray type="Float64" Name="principal_stress_values" NumberOfComponents="3" format="appended" RangeMin="2.9251501014"         RangeMax="21298.170979"         offset="5800"                />
+        <DataArray type="Float64" Name="principal_stress_vector_1" NumberOfComponents="3" format="appended" RangeMin="1"                    RangeMax="1"                    offset="6188"                />
+        <DataArray type="Float64" Name="principal_stress_vector_2" NumberOfComponents="3" format="appended" RangeMin="1"                    RangeMax="1"                    offset="6340"                />
+        <DataArray type="Float64" Name="principal_stress_vector_3" NumberOfComponents="3" format="appended" RangeMin="1"                    RangeMax="1"                    offset="6496"                />
+      </CellData>
+      <Points>
+        <DataArray type="Float64" Name="Points" NumberOfComponents="3" format="appended" RangeMin="0"                    RangeMax="1.4142135624"         offset="6568"                />
+      </Points>
+      <Cells>
+        <DataArray type="Int64" Name="connectivity" format="appended" RangeMin=""                     RangeMax=""                     offset="6820"                />
+        <DataArray type="Int64" Name="offsets" format="appended" RangeMin=""                     RangeMax=""                     offset="6984"                />
+        <DataArray type="UInt8" Name="types" format="appended" RangeMin=""                     RangeMax=""                     offset="7092"                />
+      </Cells>
+    </Piece>
+  </UnstructuredGrid>
+  <AppendedData encoding="base64">
+   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+  </AppendedData>
+</VTKFile>
diff --git a/Tests/Data/HydroMechanics/HydraulicDeactivation/simHM_deactivate_H.prj b/Tests/Data/HydroMechanics/HydraulicDeactivation/simHM_deactivate_H.prj
new file mode 100644
index 0000000000000000000000000000000000000000..768cac48a0f98b2162eb5b72855cec0b8d1d5a06
--- /dev/null
+++ b/Tests/Data/HydroMechanics/HydraulicDeactivation/simHM_deactivate_H.prj
@@ -0,0 +1,273 @@
+<?xml version='1.0' encoding='ISO-8859-1'?>
+<OpenGeoSysProject>
+    <meshes>
+        <mesh>unit_square_domain.vtu</mesh>
+        <mesh>unit_square_left.vtu</mesh>
+        <mesh>unit_square_right.vtu</mesh>
+        <mesh>unit_square_bottom.vtu</mesh>
+        <mesh>unit_square_top.vtu</mesh>
+    </meshes>
+    <processes>
+        <process>
+            <name>HM</name>
+            <type>HYDRO_MECHANICS</type>
+            <integration_order>2</integration_order>
+            <process_variables>
+                <pressure>pressure</pressure>
+                <displacement>displacement</displacement>
+            </process_variables>
+            <secondary_variables>
+                <secondary_variable internal_name="sigma" output_name="sigma"/>
+                <secondary_variable internal_name="epsilon" output_name="epsilon"/>
+            </secondary_variables>
+            <specific_body_force>0 -9.81</specific_body_force>  
+            <constitutive_relation id="0">
+                <type>LinearElasticIsotropic</type>
+                <youngs_modulus>E</youngs_modulus>
+                <poissons_ratio>nu</poissons_ratio>
+            </constitutive_relation>
+        </process>
+    </processes>
+    <media>
+        <medium id="0,2,4">
+            <phases>
+                <phase>
+                    <type>AqueousLiquid</type>
+                    <properties>
+                        <property>
+                            <name>viscosity</name>
+                            <type>Constant</type>
+                            <value> 1.e-3 </value>
+                        </property>
+                        <property>
+                            <name>density</name>
+                            <type>Constant</type>
+                            <value> 1.e3 </value>
+                        </property>
+                    </properties>
+                </phase>
+                <phase>
+                    <type>Solid</type>
+                    <properties>
+                        <property>
+                            <name>density</name>
+                            <type>Constant</type>
+                            <value>2500.0</value>
+                        </property>
+                    </properties>
+                </phase>
+            </phases>
+            <properties>
+                <property>
+                    <name>biot_coefficient</name>
+                    <type>Constant</type>
+                    <value>1</value>
+                </property>
+                <property>
+                    <name>permeability</name>
+                    <type>Constant</type>
+                    <value>1e-14</value>
+                </property>
+                <property>
+                    <name>reference_temperature</name>
+                    <type>Constant</type>
+                    <value>293.15</value>
+                </property>
+                <property>
+                    <name>porosity</name>
+                    <type>Constant</type>
+                    <value>0.1</value>
+                </property>
+            </properties>
+        </medium>
+        <medium id="1,3">
+            <phases>
+                <phase>
+                    <type>AqueousLiquid</type>
+                    <properties>
+                        <property>
+                            <name>viscosity</name>
+                            <type>Constant</type>
+                            <value> 1.e-3 </value>
+                        </property>
+                        <property>
+                            <name>density</name>
+                            <type>Constant</type>
+                            <value> 1.e3 </value>
+                        </property>
+                    </properties>
+                </phase>
+                <phase>
+                    <type>Solid</type>
+                    <properties>
+                        <property>
+                            <name>density</name>
+                            <type>Constant</type>
+                            <value>2500.0</value>
+                        </property>
+                    </properties>
+                </phase>
+            </phases>
+            <properties>
+                <property>
+                    <name>biot_coefficient</name>
+                    <type>Constant</type>
+                    <value>0.0</value>
+                </property>
+                <property>
+                    <name>permeability</name>
+                    <type>Constant</type>
+                    <value>1e-14</value>
+                </property>
+                <property>
+                    <name>reference_temperature</name>
+                    <type>Constant</type>
+                    <value>293.15</value>
+                </property>
+                <property>
+                    <name>porosity</name>
+                    <type>Constant</type>
+                    <value>0.0</value>
+                </property>
+            </properties>
+        </medium>
+    </media>
+    <parameters>
+        <parameter>
+            <name>E</name>
+            <type>Constant</type>
+            <value>1e8</value>
+        </parameter>
+        <parameter>
+            <name>nu</name>
+            <type>Constant</type>
+            <value>0.3</value>
+        </parameter>
+        <parameter>
+            <name>InitialDisplacement</name>
+            <type>Constant</type>
+            <values>0 0</values>
+        </parameter>
+        <parameter>
+            <name>InitialPressure</name>
+            <type>Constant</type>
+            <values>0</values>
+        </parameter>
+        <parameter>
+            <name>zero</name>
+            <type>Constant</type>
+            <values>0</values>
+        </parameter>
+        <parameter>
+            <name>influx</name>
+            <type>Constant</type>
+            <values>0</values>
+        </parameter>
+    </parameters>
+    <process_variables>
+        <process_variable>
+            <name>pressure</name>
+            <components>1</components>
+            <order>1</order>
+            <initial_condition>InitialPressure</initial_condition>
+            <boundary_conditions>
+                <boundary_condition>
+                    <mesh>unit_square_top</mesh>
+                    <type>Dirichlet</type>
+                    <parameter>zero</parameter>
+                </boundary_condition>
+            </boundary_conditions>
+            <deactivated_subdomains>
+                <deactivated_subdomain>
+                    <time_interval>
+                        <start>0</start>
+                        <end>1</end>
+                    </time_interval>
+                    <material_ids>1 3</material_ids>
+                </deactivated_subdomain>
+            </deactivated_subdomains>
+        </process_variable>
+        <process_variable>
+            <name>displacement</name>
+            <components>2</components>
+            <order>1</order>
+            <initial_condition>InitialDisplacement</initial_condition>
+            <boundary_conditions>
+                <boundary_condition>
+                    <mesh>unit_square_left</mesh>
+                    <type>Dirichlet</type>
+                    <component>0</component>
+                    <parameter>zero</parameter>
+                </boundary_condition>
+                <boundary_condition>
+                    <mesh>unit_square_right</mesh>
+                    <type>Dirichlet</type>
+                    <component>0</component>
+                    <parameter>zero</parameter>
+                </boundary_condition>
+                <boundary_condition>
+                    <mesh>unit_square_bottom</mesh>
+                    <type>Dirichlet</type>
+                    <component>1</component>
+                    <parameter>zero</parameter>
+                </boundary_condition>
+            </boundary_conditions>
+        </process_variable>
+    </process_variables>
+    <time_loop>
+        <processes>
+            <process ref="HM">
+                <time_stepping>
+                    <type>FixedTimeStepping</type>
+                    <t_initial>0.0</t_initial>
+                    <t_end>1</t_end>
+                    <timesteps>
+                        <pair>
+                            <repeat>1</repeat>
+                            <delta_t>1</delta_t>
+                        </pair>
+                    </timesteps>
+                </time_stepping>
+                <nonlinear_solver>basic_newton</nonlinear_solver>
+                <convergence_criterion>
+                    <type>PerComponentDeltaX</type>
+                    <norm_type>NORM2</norm_type>
+                    <abstols>1e-2 1e-6 1e-6</abstols>
+                </convergence_criterion>
+                <time_discretization>
+                    <type>BackwardEuler</type>
+                </time_discretization>
+            </process>
+        </processes>
+        <output>
+            <type>VTK</type>
+            <prefix>hydraulic_deactivation</prefix>
+            <suffix>_ts_{:timestep}_t_{:0.0etime}</suffix>
+            <timesteps>
+                <pair>
+                    <repeat>1</repeat>
+                    <each_steps>1</each_steps>
+                </pair>
+            </timesteps>
+            <variables>
+            </variables>
+        </output>
+    </time_loop>
+    <linear_solvers>
+        <linear_solver>
+            <name>direct_linear_solver</name>
+            <eigen>
+                <solver_type>SparseLU</solver_type>
+                <scaling>false</scaling>
+            </eigen>
+        </linear_solver>
+    </linear_solvers>
+    <nonlinear_solvers>
+        <nonlinear_solver>
+            <name>basic_newton</name>
+            <type>Newton</type>
+            <max_iter>30</max_iter>
+            <linear_solver>direct_linear_solver</linear_solver>
+        </nonlinear_solver>
+    </nonlinear_solvers>
+</OpenGeoSysProject>
diff --git a/Tests/Data/HydroMechanics/HydraulicDeactivation/unit_square_bottom.vtu b/Tests/Data/HydroMechanics/HydraulicDeactivation/unit_square_bottom.vtu
new file mode 100644
index 0000000000000000000000000000000000000000..098f3409ea60f05e1e60dca60d9327c9750511fe
--- /dev/null
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