diff --git a/domain/sap10_calculator/rdsap/cert_to_inputs.py b/domain/sap10_calculator/rdsap/cert_to_inputs.py
index 97adc7ad3..21b05af9b 100644
--- a/domain/sap10_calculator/rdsap/cert_to_inputs.py
+++ b/domain/sap10_calculator/rdsap/cert_to_inputs.py
@@ -6592,6 +6592,18 @@ def _primary_loss_applies(
     # kWh/yr — zero before this branch.
     if water_heating_code in _WATER_HEATING_BOILER_CIRCULATOR_CODES:
         return True
+    # SAP 10.2 §4.3 "Heat networks" (PDF p.24), scoped "Where hot water is
+    # provided by a heat network": "Primary circuit loss for insulated
+    # pipework and cylinderstat should be included (see Table 3)." A water-
+    # ONLY community scheme (WHC 950/951/952) feeds the dwelling-side
+    # cylinder via primary pipework from the network connection whatever
+    # the space main is, so the loss applies exactly as for heat-network
+    # mains with WHC 901/902/914 (below). Checked off `water_heating_code`
+    # before the main-keyed branches so a non-boiler space main (warm air,
+    # HP, direct-acting electric) can't zero it out — cert 9093 is the
+    # cohort case (whc 950 + warm-air main 502).
+    if water_heating_code in _WATER_HEAT_NETWORK_ONLY_CODES:
+        return True
     # SAP 10.2 Table 3 (PDF p.160) zero-loss list names "Direct-acting
     # electric boiler" verbatim. RdSAP 10 §12 (p.62) classifies SAP code
     # 191 as the direct-acting electric boiler: its cylinder is immersion-