diff --git a/CMakeLists_files.cmake b/CMakeLists_files.cmake
index 119ab033643..220ae321fc1 100644
--- a/CMakeLists_files.cmake
+++ b/CMakeLists_files.cmake
@@ -242,6 +242,7 @@ if(ENABLE_ECL_INPUT)
     src/opm/material/fluidsystems/blackoilpvt/Co2GasPvt.cpp
     src/opm/material/fluidsystems/blackoilpvt/ConstantCompressibilityBrinePvt.cpp
     src/opm/material/fluidsystems/blackoilpvt/ConstantCompressibilityOilPvt.cpp
+    src/opm/material/fluidsystems/blackoilpvt/ConstantCompressibilityWaterPvt.cpp
   )
 
 
diff --git a/opm/material/fluidsystems/blackoilpvt/ConstantCompressibilityWaterPvt.hpp b/opm/material/fluidsystems/blackoilpvt/ConstantCompressibilityWaterPvt.hpp
index a05968a1dd3..5be4bf36cc0 100644
--- a/opm/material/fluidsystems/blackoilpvt/ConstantCompressibilityWaterPvt.hpp
+++ b/opm/material/fluidsystems/blackoilpvt/ConstantCompressibilityWaterPvt.hpp
@@ -27,13 +27,17 @@
 #ifndef OPM_CONSTANT_COMPRESSIBILITY_WATER_PVT_HPP
 #define OPM_CONSTANT_COMPRESSIBILITY_WATER_PVT_HPP
 
-#if HAVE_ECL_INPUT
-#include <opm/input/eclipse/EclipseState/EclipseState.hpp>
-#endif
-
+#include <cstddef>
+#include <stdexcept>
 #include <vector>
 
 namespace Opm {
+
+#if HAVE_ECL_INPUT
+class EclipseState;
+class Schedule;
+#endif
+
 /*!
  * \brief This class represents the Pressure-Volume-Temperature relations of the gas phase
  *        without vaporized oil.
@@ -42,47 +46,12 @@ template <class Scalar>
 class ConstantCompressibilityWaterPvt
 {
 public:
-    ConstantCompressibilityWaterPvt() = default;
-    ConstantCompressibilityWaterPvt(const std::vector<Scalar>& waterReferenceDensity,
-                                    const std::vector<Scalar>& waterReferencePressure,
-                                    const std::vector<Scalar>& waterReferenceFormationVolumeFactor,
-                                    const std::vector<Scalar>& waterCompressibility,
-                                    const std::vector<Scalar>& waterViscosity,
-                                    const std::vector<Scalar>& waterViscosibility)
-        : waterReferenceDensity_(waterReferenceDensity)
-        , waterReferencePressure_(waterReferencePressure)
-        , waterReferenceFormationVolumeFactor_(waterReferenceFormationVolumeFactor)
-        , waterCompressibility_(waterCompressibility)
-        , waterViscosity_(waterViscosity)
-        , waterViscosibility_(waterViscosibility)
-    { }
 #if HAVE_ECL_INPUT
     /*!
      * \brief Sets the pressure-dependent water viscosity and density
      *        using a table stemming from the Eclipse PVTW keyword.
      */
-    void initFromState(const EclipseState& eclState, const Schedule&)
-    {
-        const auto& pvtwTable = eclState.getTableManager().getPvtwTable();
-        const auto& densityTable = eclState.getTableManager().getDensityTable();
-
-        assert(pvtwTable.size() == densityTable.size());
-
-        size_t numRegions = pvtwTable.size();
-        setNumRegions(numRegions);
-
-        for (unsigned regionIdx = 0; regionIdx < numRegions; ++ regionIdx) {
-            waterReferenceDensity_[regionIdx] = densityTable[regionIdx].water;
-
-            waterReferencePressure_[regionIdx] = pvtwTable[regionIdx].reference_pressure;
-            waterReferenceFormationVolumeFactor_[regionIdx] = pvtwTable[regionIdx].volume_factor;
-            waterCompressibility_[regionIdx] = pvtwTable[regionIdx].compressibility;
-            waterViscosity_[regionIdx] = pvtwTable[regionIdx].viscosity;
-            waterViscosibility_[regionIdx] = pvtwTable[regionIdx].viscosibility;
-        }
-
-        initEnd();
-    }
+    void initFromState(const EclipseState& eclState, const Schedule&);
 #endif
 
     void setNumRegions(size_t numRegions)
@@ -271,7 +240,7 @@ class ConstantCompressibilityWaterPvt
                                              const Evaluation& /*saltconcentration*/) const
     { return 0.0; /* this is dead water! */ }
 
-    const Scalar waterReferenceDensity(unsigned regionIdx) const
+    Scalar waterReferenceDensity(unsigned regionIdx) const
     { return waterReferenceDensity_[regionIdx]; }
 
     const std::vector<Scalar>& waterReferencePressure() const
@@ -289,16 +258,6 @@ class ConstantCompressibilityWaterPvt
     const std::vector<Scalar>& waterViscosibility() const
     { return waterViscosibility_; }
 
-    bool operator==(const ConstantCompressibilityWaterPvt<Scalar>& data) const
-    {
-        return this->waterReferenceDensity_ == data.waterReferenceDensity_ &&
-               this->waterReferencePressure() == data.waterReferencePressure() &&
-               this->waterReferenceFormationVolumeFactor() == data.waterReferenceFormationVolumeFactor() &&
-               this->waterCompressibility() == data.waterCompressibility() &&
-               this->waterViscosity() == data.waterViscosity() &&
-               this->waterViscosibility() == data.waterViscosibility();
-    }
-
 private:
     std::vector<Scalar> waterReferenceDensity_;
     std::vector<Scalar> waterReferencePressure_;
diff --git a/src/opm/material/fluidsystems/blackoilpvt/ConstantCompressibilityWaterPvt.cpp b/src/opm/material/fluidsystems/blackoilpvt/ConstantCompressibilityWaterPvt.cpp
new file mode 100644
index 00000000000..c09f7ee2e55
--- /dev/null
+++ b/src/opm/material/fluidsystems/blackoilpvt/ConstantCompressibilityWaterPvt.cpp
@@ -0,0 +1,67 @@
+// -*- mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+// vi: set et ts=4 sw=4 sts=4:
+/*
+  This file is part of the Open Porous Media project (OPM).
+
+  OPM is free software: you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation, either version 2 of the License, or
+  (at your option) any later version.
+
+  OPM is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License
+  along with OPM.  If not, see <http://www.gnu.org/licenses/>.
+
+  Consult the COPYING file in the top-level source directory of this
+  module for the precise wording of the license and the list of
+  copyright holders.
+*/
+
+#include <config.h>
+#include <opm/material/fluidsystems/blackoilpvt/ConstantCompressibilityWaterPvt.hpp>
+
+#include <opm/common/ErrorMacros.hpp>
+
+#include <opm/input/eclipse/EclipseState/EclipseState.hpp>
+
+#include <fmt/format.h>
+
+namespace Opm {
+
+template<class Scalar>
+void ConstantCompressibilityWaterPvt<Scalar>::
+initFromState(const EclipseState& eclState, const Schedule&)
+{
+    const auto& pvtwTable = eclState.getTableManager().getPvtwTable();
+    const auto& densityTable = eclState.getTableManager().getDensityTable();
+
+    if (pvtwTable.size() != densityTable.size()) {
+        OPM_THROW(std::runtime_error,
+                  fmt::format("Table sizes mismatch. PVTW: {}, DensityTable: {}\n",
+                              pvtwTable.size(), densityTable.size()));
+    }
+
+    size_t numRegions = pvtwTable.size();
+    setNumRegions(numRegions);
+
+    for (unsigned regionIdx = 0; regionIdx < numRegions; ++regionIdx) {
+        waterReferenceDensity_[regionIdx] = densityTable[regionIdx].water;
+
+        waterReferencePressure_[regionIdx] = pvtwTable[regionIdx].reference_pressure;
+        waterReferenceFormationVolumeFactor_[regionIdx] = pvtwTable[regionIdx].volume_factor;
+        waterCompressibility_[regionIdx] = pvtwTable[regionIdx].compressibility;
+        waterViscosity_[regionIdx] = pvtwTable[regionIdx].viscosity;
+        waterViscosibility_[regionIdx] = pvtwTable[regionIdx].viscosibility;
+    }
+
+    initEnd();
+}
+
+template class ConstantCompressibilityWaterPvt<double>;
+template class ConstantCompressibilityWaterPvt<float>;
+
+} // namespace Opm