Flooded Patio when rains drainage advice

[GlennSpray68]

Hi all, any advice very gratefully received.
I am wanting to replace my patio, with new slabs.
Before replacing it, I have an issue with the current patio that, rainwater pools against the retaining wall after heavy rain.
When I install the new patio I wish to prevent the same problem occurring by installing some acco drainage at the retaining wall junction.
There is a main hole cover on the patio that accesses the sewage drains,
Would I be able to and how would I connect to it as it isn't a modern plastic one, but a brick built one.
I have attached a couple of pics for information purposes.
Best regards
Glenn

 

[blup]

Surface water draining into a foul sewer is not generally permitted afaik. If you did it, probably easiest to dismantle and rebuild the chamber wall where the pipe would enter, and make good with mortar. But a separate soakaway is the correct way.