I live in Melbourne. What size of storm water pipe should I use 90mm or 100mm?

Thanks Eric for clarification. The photo shows only one damaged brick, but actually I have about 10 damaged bricks.

Thanks Eric. I am not sure what you meant by "giving this project a try as it is only a single brick to be replaced"?

For replacement of the spalling bricks, do you know the cost a brick layer would charge? Thanks

Thanks Eric

Thanks Brad. There are no water pipes near the area. The area is front of the house.