diff --git a/swash/processing/read_swash.py b/swash/processing/read_swash.py
index 9d1906b..ffbc3aa 100644
--- a/swash/processing/read_swash.py
+++ b/swash/processing/read_swash.py
@@ -1,3 +1,6 @@
+import subprocess
+import tempfile
+
 import numpy as np
 
 
@@ -7,43 +10,44 @@ class ReadSwash:
         self._n_t = None
         self._t = None
         self._x = None
-        self._data = {}
 
     @classmethod
     def read_nohead(cls, path):
-        with open(path) as file:
-            return np.asarray(file.read().split(), dtype=np.float64)
+        with open(path) as file, tempfile.TemporaryFile() as tmpfile:
+            subprocess.run(("tr", "-d", "\n"), stdin=file, stdout=tmpfile)
+            return np.loadtxt(tmpfile)
 
     def read_time(self, path):
         self._t = np.unique(self.read_nohead(path))
         self._n_t = self._t.size
+        return self.t
 
     def read_x(self, path):
         self._x = np.unique(self.read_nohead(path))
         self._n_x = self._x.size
+        return self.x
 
     def read_scalar(self, path, const=False):
         if const:
-            self._data[path.stem] = self.read_nohead(path).reshape(
+            return self.read_nohead(path).reshape(
                 (self._n_t, self._n_x)
             )[0, :]
-            return
-        self._data[path.stem] = self.read_nohead(path).reshape(
+        return self.read_nohead(path).reshape(
             (self._n_t, self._n_x)
         )
 
     def read_vector(self, path):
-        self._data[path.stem] = self.read_nohead(path).reshape(
+        return self.read_nohead(path).reshape(
             (self._n_t, 2, self._n_x)
         )
 
     def read_scalar_lay(self, path):
-        self._data[path.stem] = self.read_nohead(path).reshape(
+        return self.read_nohead(path).reshape(
             (self._n_t, -1, self._n_x)
         )
 
     def read_vector_lay(self, path):
-        self._data[path.stem] = self.read_nohead(path).reshape(
+        return self.read_nohead(path).reshape(
             (self._n_t, 2, -1, self._n_x)
         )
 
@@ -54,7 +58,3 @@ class ReadSwash:
     @property
     def x(self):
         return self._x
-
-    @property
-    def data(self):
-        return self._data
diff --git a/swash/processing/sws_npz.py b/swash/processing/sws_npz.py
index 815d138..011bdce 100644
--- a/swash/processing/sws_npz.py
+++ b/swash/processing/sws_npz.py
@@ -27,15 +27,14 @@ rsws = ReadSwash()
 rsws.read_time(sws_out.joinpath("tsec.dat"))
 rsws.read_x(sws_out.joinpath("xp.dat"))
 
-log.info("Reading 'dep'")
-rsws.read_scalar(sws_out.joinpath("dep.dat"))
-log.info("Reading 'botl'")
-rsws.read_scalar(sws_out.joinpath("botl.dat"), const=True)
-log.info("Reading 'watl'")
-rsws.read_scalar(sws_out.joinpath("watl.dat"))
-log.info("Reading 'vel'")
-rsws.read_vector(sws_out.joinpath("vel.dat"))
-
-log.info(f"Writing npz file in '{inp}'")
 inp.mkdir(exist_ok=True)
-np.savez_compressed(inp.joinpath("sws"), t=rsws.t, x=rsws.x, **rsws.data)
+log.info(f"Wrinting output in '{inp}'")
+log.info("Reading 'dep'")
+np.save(inp.joinpath("dep"), rsws.read_scalar(sws_out.joinpath("dep.dat")))
+log.info("Reading 'botl'")
+np.save(inp.joinpath("botl"), rsws.read_scalar(sws_out.joinpath("botl.dat"),
+    const=True))
+log.info("Reading 'watl'")
+np.save(inp.joinpath("watl"), rsws.read_scalar(sws_out.joinpath("watl.dat")))
+log.info("Reading 'vel'")
+np.save(inp.joinpath("vel"), rsws.read_vector(sws_out.joinpath("vel.dat")))