DIY Doctor UK DIY Forums

Hi, I have a built up of drainage smell in the basement where we us to have are old toilet drainage before, basically the old drainage is no longer in use and still has water standing, its under the bay window in the basement. I can access it by removing a few bricks from inside the basement as its under ground,

Now I was wondering what's the best way to close out the smell and completely close the old drainage? Sandbags then concrete cement? Any suggestions

Many Thanks