diff --git a/convert.lua b/convert.lua
deleted file mode 100644
index d707b40..0000000
--- a/convert.lua
+++ /dev/null
@@ -1,79 +0,0 @@
---[[
-
-	Tube Library 2
-	==============
-
-	Copyright (C) 2017-2018 Joachim Stolberg
-
-	LGPLv2.1+
-	See LICENSE.txt for more information
-
-	convert.lua
-
-    Optional module, only needed to convert legacy tubes into tubelib2 tubes.
-    This is done by means of a callback function:
-	    dir1, dir2, num = func(pos, name, param2)
-
-]]--
-
--- for lazy programmers
-local M = minetest.get_meta
-
-local Tube = tubelib2.Tube
-
-function Tube:on_convert_tube(convert_tube_clbk)
-	self.convert_tube_clbk = convert_tube_clbk
-end
-
--- Register legacy tube nodes.
-function Tube:add_legacy_node_names(names)
-	for _,name in ipairs(names) do
-		self.legacy_node_names[name] = true
-	end
-end
-
-
-function Tube:convert_tube_line(pos, dir)
-	local convert_next_tube = function(self, pos, dir)
-		local npos, node = self:get_node(pos, dir)
-		if self.legacy_node_names[node.name]  then
-			local dir1, dir2, num
-			if self.convert_tube_clbk then
-				dir1, dir2, num = self.convert_tube_clbk(npos, node.name, node.param2)
-			else
-				dir1, dir2, num = self:determine_dir1_dir2_and_num_conn(npos)
-			end
-			if dir1 then
-				self.clbk_after_place_tube(self:tube_data_to_table(npos, dir1, 
-					dir2 or tubelib2.Turn180Deg[dir1], num))
-				if tubelib2.Turn180Deg[dir] == dir1 then
-					return npos, dir2
-				else
-					return npos, dir1
-				end
-			end
-		end
-	end
-	
-	local cnt = 0
-	if not dir then	return pos, cnt end	
-	while cnt <= 100000 do
-		local new_pos, new_dir = convert_next_tube(self, pos, dir)
-		if not new_dir then	break end
-		pos, dir = new_pos, new_dir
-		cnt = cnt + 1
-	end
-	return pos, dir, cnt
-end	
-
-function Tube:set_pairing(pos, peer_pos)
-	
-	M(pos):set_int("tube_dir", self:get_primary_dir(pos))
-	M(peer_pos):set_int("tube_dir", self:get_primary_dir(peer_pos))
-	
-	local tube_dir1 = self:store_teleport_data(pos, peer_pos)
-	local tube_dir2 = self:store_teleport_data(peer_pos, pos)
-
-	self:delete_tube_meta_data(pos, tube_dir1)
-	self:delete_tube_meta_data(peer_pos, tube_dir2)
-end
diff --git a/init.lua b/init.lua
index dd89f80..a6e7a4c 100644
--- a/init.lua
+++ b/init.lua
@@ -3,6 +3,5 @@ tubelib2 = {}
 dofile(minetest.get_modpath("tubelib2") .. "/tube_api.lua")
 dofile(minetest.get_modpath("tubelib2") .. "/internal2.lua")
 dofile(minetest.get_modpath("tubelib2") .. "/internal1.lua")
-dofile(minetest.get_modpath("tubelib2") .. "/convert.lua")
 -- Only for testing/demo purposes
 dofile(minetest.get_modpath("tubelib2") .. "/tube_test.lua")
diff --git a/internal1.lua b/internal1.lua
index 907f769..3fd7e1f 100644
--- a/internal1.lua
+++ b/internal1.lua
@@ -22,6 +22,7 @@ local M = minetest.get_meta
 local Tube = tubelib2.Tube
 local Turn180Deg = tubelib2.Turn180Deg
 local Dir6dToVector = tubelib2.Dir6dToVector
+local tValidNum = {[0] = true, true, true}  -- 0..2 are valid
 
 --------------------------------------------------------------------------------------
 -- node get/test functions
@@ -182,7 +183,7 @@ function Tube:update_after_place_node(pos, dirs)
 	dirs = dirs or self.dirs_to_check
 	for _,dir in ipairs(dirs) do
 		local npos, d1, d2, num = self:add_tube_dir(pos, dir)
-		if npos then
+		if npos and self.valid_dirs[d1] and self.valid_dirs[d2] and tValidNum[num]then
 			self.clbk_after_place_tube(self:tube_data_to_table(npos, d1, d2, num))
 			lRes[#lRes+1] = dir
 		end
@@ -196,7 +197,7 @@ function Tube:update_after_dig_node(pos, dirs)
 	dirs = dirs or self.dirs_to_check
 	for _,dir in ipairs(dirs) do
 		local npos, d1, d2, num = self:del_tube_dir(pos, dir)
-		if npos then
+		if npos and self.valid_dirs[d1] and self.valid_dirs[d2] and tValidNum[num]then
 			self.clbk_after_place_tube(self:tube_data_to_table(npos, d1, d2, num))
 			lRes[#lRes+1] = dir
 		end
@@ -210,19 +211,20 @@ function Tube:update_after_place_tube(pos, placer, pointed_thing)
 	if dir1 == nil then
 		return false
 	end
-	
-	self.clbk_after_place_tube(self:tube_data_to_table(pos, dir1, dir2, num_tubes))
+	if self.valid_dirs[dir1] and self.valid_dirs[dir2] and tValidNum[num_tubes]then
+		self.clbk_after_place_tube(self:tube_data_to_table(pos, dir1, dir2, num_tubes))
+	end
 	
 	if num_tubes >= 1 then
 		local npos, d1, d2, num = self:add_tube_dir(pos, dir1)
-		if npos then
+		if npos and self.valid_dirs[d1] and self.valid_dirs[d2] and tValidNum[num]then
 			self.clbk_after_place_tube(self:tube_data_to_table(npos, d1, d2, num))
 		end
 	end
 	
 	if num_tubes >= 2 then
 		local npos, d1, d2, num = self:add_tube_dir(pos, dir2)
-		if npos then
+		if npos and self.valid_dirs[d1] and self.valid_dirs[d2] and tValidNum[num]then
 			self.clbk_after_place_tube(self:tube_data_to_table(npos, d1, d2, num))
 		end
 	end
@@ -234,13 +236,13 @@ function Tube:update_after_dig_tube(pos, param2)
 	
 	local lRes = {}
 	local npos, d1, d2, num = self:del_tube_dir(pos, dir1)
-	if npos then
+	if npos and self.valid_dirs[d1] and self.valid_dirs[d2] and tValidNum[num]then
 		self.clbk_after_place_tube(self:tube_data_to_table(npos, d1, d2, num))
 		lRes[#lRes+1] = dir1
 	end
 	
 	npos, d1, d2, num = self:del_tube_dir(pos, dir2)
-	if npos then
+	if npos and self.valid_dirs[d1] and self.valid_dirs[d2] and tValidNum[num]then
 		self.clbk_after_place_tube(self:tube_data_to_table(npos, d1, d2, num))
 		lRes[#lRes+1] = dir2
 	end
diff --git a/internal2.lua b/internal2.lua
index cf5de8f..e3d1e1c 100644
--- a/internal2.lua
+++ b/internal2.lua
@@ -116,11 +116,11 @@ local Tube = tubelib2.Tube
 
 function Tube:fdir(player)
 	local pitch = player:get_look_pitch()
-	if pitch > 1.1 and self.allowed_6d_dirs[6] then -- up?
+	if pitch > 1.1 and self.valid_dirs[6] then -- up?
 		return 6
-	elseif pitch < -1.1 and self.allowed_6d_dirs[5] then -- down?
+	elseif pitch < -1.1 and self.valid_dirs[5] then -- down?
 		return 5
-	elseif not self.allowed_6d_dirs[1] then
+	elseif not self.valid_dirs[1] then
 		return 6
 	else
 		return minetest.dir_to_facedir(player:get_look_dir()) + 1
@@ -203,7 +203,7 @@ end
 -- and the players fdir and return dir1, dir2 and the number of tubes to connect to (0..2).
 function Tube:determine_tube_dirs(pos, preferred_pos, fdir)
 	local tbl = {}
-	local allowed = table.copy(self.allowed_6d_dirs)
+	local allowed = table.copy(self.valid_dirs)
 	
 	-- Check for primary nodes (tubes)
 	for dir = 1,6 do
diff --git a/tube_api.lua b/tube_api.lua
index 4f9eaff..02783b7 100644
--- a/tube_api.lua
+++ b/tube_api.lua
@@ -52,7 +52,7 @@ function Tube:new(attr)
 		clbk_after_place_tube = attr.after_place_tube,
 		pairingList = {}, -- teleporting nodes
 	}
-	o.allowed_6d_dirs = Tbl(o.dirs_to_check)
+	o.valid_dirs = Tbl(o.dirs_to_check)
 	setmetatable(o, self)
 	self.__index = self
 	return o