Where for any purpose of this Act any urban authority deem it necessary to raise sink or otherwise alter the situation of any water or gas pipes mains plugs or other waterworks or gasworks laid in or under any street, they may by notice in writing require the owner of the pipes mains plugs or works -to raise sink or otherwise alter the situation of the same in such manner and within such reasonable time as is specified in the notice ; the expenses of or connected with any such alteration shall be paid by the urban authority ; and if such notice is not complied with the urban authority may themselves make the alteration required:

Provided—

• That no such alteration shall be required or made which will permanently injure any such pipes mains plugs or works or prevent the water or gas from flowing as freely and conveniently as usual; and

• That where under any local Act of Parliament the expenses of or connected with the raising sinking or otherwise altering-the situation of any water or gas pipes mains plugs or other waterworks or gasworks, are directed to be borne by the owner of such pipes or works, his liability in that respect shall continue in the same manner and under the same conditions in all respects as if this Act had not been passed.