The concrete/mortar (?) around the base of our w.c. waste pipe (cast iron) is crumbling exposing the connection to - well whatever the next section is. I could just fill with new mortar mix but is that what should be done? Is there anything I should/could do to make sure it stays sealed - maybe before cementing over the area? The water in the pic is just from a bucket of water I poured over it to clean out the bits. The joint itself doesn't appear to be leaking although it is corroded. Thanks
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