diff --git a/process/data_structure/vacuum_variables.py b/process/data_structure/vacuum_variables.py
index 25204f6856..b0cd721ee7 100644
--- a/process/data_structure/vacuum_variables.py
+++ b/process/data_structure/vacuum_variables.py
@@ -1,4 +1,12 @@
 from dataclasses import dataclass
+from enum import IntEnum
+
+
+class VacuumPumpType(IntEnum):
+    """Enum for vacuum pump types. Controlled via `i_vacuum_pump_type` in `VacuumData`."""
+
+    TURBOMOLECULAR = 0
+    COMPOUND_CRYOPUMP = 1
 
 
 @dataclass(slots=True)
diff --git a/process/models/vacuum.py b/process/models/vacuum.py
index 39f2be1786..5fc3c998e5 100644
--- a/process/models/vacuum.py
+++ b/process/models/vacuum.py
@@ -8,6 +8,7 @@
 from process.core import constants, process_output
 from process.core import process_output as po
 from process.core.model import Model
+from process.data_structure.vacuum_variables import VacuumPumpType
 from process.models.build import FwBlktVVShape
 from process.models.engineering.ivc_functions import dshellvol, eshellvol
 
@@ -312,7 +313,8 @@ def vacuum(
         # nitrogen, DT, helium, DT again
         sp = (
             [1.95, 1.8, 1.8, 1.8]
-            if self.data.vacuum.i_vacuum_pump_type == 0
+            if VacuumPumpType(self.data.vacuum.i_vacuum_pump_type)
+            == VacuumPumpType.TURBOMOLECULAR
             else [9.0, 25.0, 5.0, 25.0]
         )
 
@@ -512,7 +514,10 @@ def vacuum(
         #  If cryopumps are used then an additional pump is required
         #  for continuous operation with regeneration.
 
-        if self.data.vacuum.i_vacuum_pump_type == 1:
+        if (
+            VacuumPumpType(self.data.vacuum.i_vacuum_pump_type)
+            == VacuumPumpType.COMPOUND_CRYOPUMP
+        ):
             pumpn *= 2.0e0
 
         #  Information for costing routine
@@ -658,7 +663,10 @@ def vacuum(
                 process_output.oblnkl(self.outfile)
 
             i_fw_blkt_shared_coolant = (
-                "cryo " if self.data.vacuum.i_vacuum_pump_type == 1 else "turbo"
+                "cryo "
+                if VacuumPumpType(self.data.vacuum.i_vacuum_pump_type)
+                == VacuumPumpType.COMPOUND_CRYOPUMP
+                else "turbo"
             )
 
             process_output.oblnkl(self.outfile)
diff --git a/tests/unit/models/test_costs_1990.py b/tests/unit/models/test_costs_1990.py
index 831b08a72c..15819a386a 100644
--- a/tests/unit/models/test_costs_1990.py
+++ b/tests/unit/models/test_costs_1990.py
@@ -6,6 +6,7 @@
 import pytest
 
 from process.data_structure.pfcoil_variables import PFConductorModel
+from process.data_structure.vacuum_variables import VacuumPumpType
 from process.models.engineering.pumping import CoolantType
 from process.models.superconductors import (
     SuperconductorModel,
@@ -2936,7 +2937,7 @@ class Acc224Param(NamedTuple):
             m_vv_vacuum_duct_shield=0,
             n_vac_pumps_high=46,
             dia_vv_vacuum_ducts=0.57081858183821432,
-            i_vacuum_pump_type=1,
+            i_vacuum_pump_type=VacuumPumpType.COMPOUND_CRYOPUMP,
             n_vv_vacuum_ducts=16,
             c22=0,
             c2245=0,
@@ -2953,7 +2954,7 @@ class Acc224Param(NamedTuple):
             m_vv_vacuum_duct_shield=0,
             n_vac_pumps_high=46,
             dia_vv_vacuum_ducts=0.57072331228476758,
-            i_vacuum_pump_type=1,
+            i_vacuum_pump_type=VacuumPumpType.COMPOUND_CRYOPUMP,
             n_vv_vacuum_ducts=16,
             c22=3474.7391916096453,
             c2245=0,
diff --git a/tests/unit/models/test_vacuum.py b/tests/unit/models/test_vacuum.py
index 7c869820e2..f1913200a2 100644
--- a/tests/unit/models/test_vacuum.py
+++ b/tests/unit/models/test_vacuum.py
@@ -2,6 +2,8 @@
 
 import pytest
 
+from process.data_structure.vacuum_variables import VacuumPumpType
+
 
 @pytest.fixture
 def vacuum(process_models):
@@ -70,7 +72,9 @@ def test_old_model(monkeypatch, vacuum):
         )
         monkeypatch.setattr(vacuum.data.times, "t_plant_pulse_coil_precharge", 30)
         monkeypatch.setattr(vacuum.data.vacuum, "i_vac_pump_dwell", 0)
-        monkeypatch.setattr(vacuum.data.vacuum, "i_vacuum_pump_type", 1)
+        monkeypatch.setattr(
+            vacuum.data.vacuum, "i_vacuum_pump_type", VacuumPumpType.COMPOUND_CRYOPUMP
+        )
         monkeypatch.setattr(
             vacuum.data.vacuum, "pres_vv_chamber_base", 0.00050000000000000001
         )