diff --git a/xos/cord/models.py b/xos/cord/models.py
index e5cd4c3..7f255d0 100644
--- a/xos/cord/models.py
+++ b/xos/cord/models.py
@@ -77,6 +77,8 @@
             self._meta.get_field("provider_service").default = volt_services[0].id
         super(VOLTTenant, self).__init__(*args, **kwargs)
 
+        self.orig_vcpe_id = self.get_initial_attribute("vcpe_id")
+
     @property
     def vlan_id(self):
         return self.get_attribute("vlan_id", self.default_attributes["vlan_id"])
@@ -166,6 +168,13 @@
             self.vcpe.delete()
             self.vcpe = None
 
+    def cleanup_orphans(self):
+        if self.orig_vcpe_id and (self.orig_vcpe_id != self.get_attribute("vcpe_id")):
+            vcpes=VCPETenant.objects.filter(id=self.orig_vcpe_id)
+            if vcpes:
+                # print "XXX clean up orphaned vcpe", vcpes[0]
+                vcpes[0].delete()
+
     def save(self, *args, **kwargs):
         self.validate_unique_service_specific_id()
 
@@ -179,6 +188,7 @@
 
         super(VOLTTenant, self).save(*args, **kwargs)
         self.manage_vcpe()
+        self.cleanup_orphans()
 
     def delete(self, *args, **kwargs):
         self.cleanup_vcpe()
@@ -243,6 +253,8 @@
         super(VCPETenant, self).__init__(*args, **kwargs)
         self.cached_vbng=None
         self.cached_sliver=None
+        self.orig_vbng_id = self.get_initial_attribute("vbng_id")
+        self.orig_sliver_id = self.get_initial_attribute("sliver_id")
 
     @property
     def image(self):
@@ -604,6 +616,21 @@
             self.vbng.delete()
             self.vbng = None
 
+    def cleanup_orphans(self):
+
+        if self.orig_vbng_id and (self.orig_vbng_id != self.get_attribute("vbng_id")):
+            vbngs=VBNGTenant.objects.filter(id=self.orig_vbng_id)
+            if vbngs:
+                # print "XXX clean up orphaned vbng", vbngs[0]
+                vbngs[0].delete()
+
+
+        if self.orig_sliver_id and (self.orig_sliver_id != self.get_attribute("sliver_id")):
+            slivers=Sliver.objects.filter(id=self.orig_sliver_id)
+            if slivers:
+                # print "XXX clean up orphaned sliver", slivers[0]
+                slivers[0].delete()
+
     def manage_bbs_account(self):
         if self.deleted:
             return
@@ -635,6 +662,7 @@
         self.manage_sliver()
         self.manage_vbng()
         self.manage_bbs_account()
+        self.cleanup_orphans()
 
     def delete(self, *args, **kwargs):
         self.cleanup_vbng()
diff --git a/xos/core/models/service.py b/xos/core/models/service.py
index 78f2792..2f01972 100644
--- a/xos/core/models/service.py
+++ b/xos/core/models/service.py
@@ -196,6 +196,34 @@
         attributes[name]=value
         self.service_specific_attribute = json.dumps(attributes)
 
+    def get_initial_attribute(self, name, default=None):
+        if self._initial["service_specific_attribute"]:
+            attributes = json.loads(self._initial["service_specific_attribute"])
+        else:
+            attributes = {}
+        return attributes.get(name, default)
+
+    def update_attribute_from_initial(self):
+        # XXX not sure I want to pursue this approach...
+        try:
+            attributes = json.loads(self._initial["service_specific_attribute"])
+        except:
+            attributes = {}
+
+        if not self.service_specific_attribute:
+            # the easy case -- nothing has changed, so keep the original
+            # attribute
+            self.service_specific_attribute = json.dumps(orig_attributes)
+            return
+
+        try:
+            new_attributes = json.loads(self.service_specific_attribute)
+        except:
+            raise XOSValidationError("Unable to parse service_specific_attribute")
+
+        attributes.update(new_attributes)
+        self.service_specific_attribute = json.dumps(attributes)
+
     @classmethod
     def get_tenant_objects(cls):
         return cls.objects.filter(kind = cls.KIND)