plumbers mait

I need to fit a new waste to a basin after removing an old one that was fitted (poorly) with silicone. I removed all lumpy bits of silicone and most of the the finer bits with silicone remover, but there is still some silicone bits left that I can't get out. What are my best options for getting...

My cast iron soil pipe does not seem to be leaking, but there are sometimes bad smells - presumably because the joints are in a poor state. Q1 - What should I use to reseal it with? A man who came about the drains suggested chemical metal. But should I use something else instead, such as...

Managed to get a small hole in the kitchen sink (see photo), which is leaking underneath. Unfortunately the sink can't be easily replaced as it's fully integrated within a granite worktop. Just wondering what's the best way to repair this? Would applying plumbers mait underneath the hole keep...