diff --git a/src/epanet.c b/src/epanet.c
index 91b9fcf..95a3712 100755
--- a/src/epanet.c
+++ b/src/epanet.c
@@ -1972,6 +1972,7 @@ int DLLEXPORT ENsetnodevalue(int index, int code, EN_API_FLOAT_TYPE v)
    int  j;
    Pdemand demand;
    Psource source;
+   double Htmp;
    double value = v;
 
    if (!Openflag) return(102);
@@ -2092,6 +2093,7 @@ int DLLEXPORT ENsetnodevalue(int index, int code, EN_API_FLOAT_TYPE v)
 
       case EN_TANKDIAM:
          if (value <= 0.0) return(202);
+         if (index <= Njuncs) return(251);
          j = index - Njuncs;
          if (j > 0 && Tank[j].A > 0.0)
          {
@@ -2101,10 +2103,15 @@ int DLLEXPORT ENsetnodevalue(int index, int code, EN_API_FLOAT_TYPE v)
             Tank[j].V0 = tankvolume(j, Tank[j].H0);
             Tank[j].Vmax = tankvolume(j, Tank[j].Hmax);
          }
+         else
+         {
+            return(251);
+         }
          break;
 
       case EN_MINVOLUME:
          if (value < 0.0) return(202);
+         if (index <= Njuncs) return(251);
          j = index - Njuncs;
          if (j > 0 && Tank[j].A > 0.0)
          {
@@ -2112,41 +2119,65 @@ int DLLEXPORT ENsetnodevalue(int index, int code, EN_API_FLOAT_TYPE v)
             Tank[j].V0 = tankvolume(j, Tank[j].H0);
             Tank[j].Vmax = tankvolume(j, Tank[j].Hmax);
          }
+         else
+         {
+            return(251);
+         }
          break;
         
       case EN_MINLEVEL:
          if (value < 0.0) return(202);
+         if (index <= Njuncs) return(251); //not a tank or reservoir
          j = index - Njuncs;
-         if (j > 0 && Tank[j].A > 0.0)
+         if (Tank[j].A == 0.0) return(251); //node is a reservoir
+         Htmp = value/Ucf[ELEV] + Node[index].El;
+         if (Htmp < Tank[j].Hmax && Htmp <= Tank[j].H0)
          {
             if (Tank[j].Vcurve > 0) return(202);
-            Tank[j].Hmin = value/Ucf[ELEV] + Node[index].El;
+            Tank[j].Hmin = Htmp;
             Tank[j].Vmin = tankvolume(j, Tank[j].Hmin);
          }
+         else
+         {
+            return(251);
+         }
          break;
 
       case EN_MAXLEVEL:
          if (value < 0.0) return(202);
+         if (index <= Njuncs) return(251); //not a tank or reservoir
          j = index - Njuncs;
-         if (j > 0 && Tank[j].A > 0.0)
+         if (Tank[j].A == 0.0) return(251); //node is a reservoir
+         Htmp = value/Ucf[ELEV] + Node[index].El;
+         if (Htmp > Tank[j].Hmin && Htmp >= Tank[j].H0)
          {
             if (Tank[j].Vcurve > 0) return(202);
-            Tank[j].Hmax = value/Ucf[ELEV] + Node[index].El;
+            Tank[j].Hmax = Htmp;
             Tank[j].Vmax = tankvolume(j, Tank[j].Hmax);
          }
+         else
+         {
+            return(251);
+         }
          break;
 
       case EN_MIXMODEL:
          j = ROUND(value);
+         if (index <= Njuncs) return(251);
          if (j < MIX1 || j > LIFO) return(202);
          if (index > Njuncs && Tank[index-Njuncs].A > 0.0)
          {
             Tank[index-Njuncs].MixModel = (char)j;
          }
+         else
+         {
+            return(251);
+         }
          break;
 
       case EN_MIXFRACTION:
          if (value < 0.0 || value > 1.0) return(202);
+         if (index <= Njuncs) return(251);
          j = index - Njuncs;
          if (j > 0 && Tank[j].A > 0.0)
          {
@@ -2155,12 +2186,17 @@ int DLLEXPORT ENsetnodevalue(int index, int code, EN_API_FLOAT_TYPE v)
          break;
 
       case EN_TANK_KBULK:
+         if (index <= Njuncs) return(251);
          j = index - Njuncs;
          if (j > 0 && Tank[j].A > 0.0)
          {
             Tank[j].Kb = value/SECperDAY;
             Reactflag = 1;
          }
+         else
+         {
+            return(251);
+         }
          break;
 
 /***  New parameter additions ends here. ***/                                  //(2.00.12 - LR)
@@ -3264,7 +3300,7 @@ void  freedata()
     }
     
 /* Free memory for node coordinates */
-   if (Coordflag == TRUE)  free(Coord);
+   if (Coordflag == TRUE) free(Coord);
 
 /* Free memory for rule base (see RULES.C) */
     freerules();