Drain smell in basement

[Fernandez]

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

 

[CBW]

One of these and then screed over if needed. https://www.screwfix.com/p/mcalpine...MIk9yb7KLA5gIVS7TtCh1GdAu8EAQYDiABEgJW0fD_BwE

 

[bobasd]

the standing water is probably in the trap - surprising if the WC has been redundant for a while.

why not locate the manhole that this WC used to drain to - pour buckets of water down the trap opening and watch where it emerges.
when you've located the redundant inlet in a manhole then pack the inlet opening with semi-dry sand and cement - push it up.
after removing the standing water, do the same to the basement trap end.
you've now rat proofed the old drainage, and typically removed any smells from the stagnant water.