Jun 14, 2020 2:10 pm
My house is on a sloppy land and slopes downwards As you go to the back of the house. We have surface water issues due to this slope and the water makes it’s way into the basement through concrete. We have been recommended to have agi drains to divert water. We are planning agi drain across the front porch and connect it to the storm water drain.
However one plumber suggests having the agi drain 1 meter away from the footing and other plumber Suggests having it right next to the footing so that the wall can be water proofed.
I did some research and looks like opinion is split. Some forums say having the agi drain next to footing can wreck the house while many YouTube videos that showcase the work Do it this way.
Does anyone know which is a better approach?
Re: Agi drain - distance from footing2
Jun 14, 2020 2:21 pm
The main purpose of agi drain is to remove hydrostatic pressure from the waterproofed retaining wall.
As the retaining wall is waterproofed and agi drain is covered with self draining material like gravel, the water soaks down the wall and into the gravel, which means that agi drain itself needs to be located as close as possible to the wall itself in order for it to be effective.
And please don't mix it up with house perimeter drainage, which indeed has to be located 1m+ away from the house footing, but it plays totally different role and generally requires concrete + clay sloping from the house slab/footing. Alternatively, spoon drains can be used too.
What will help in your case, is a drawing of what you are intending to do.
Re: Agi drain - distance from footing3
Jun 14, 2020 2:49 pm
The trench must respect a minimum 45 degree angle of repose. This is detailed in AS 3500.3 Section 7 - Surface And Subsoil Drainage Systems and also in Part 2 of the NCC, page 96.
You can download the NCC free of charge.
BTW, the ag pipe is not allowed to connect directly to a LPOD without first draining through a silt pit but a plumber will or at least should know this.
Re: Agi drain - distance from footing5
Jun 15, 2020 7:51 am
The finished surface should also slope away from the house. It sounds like you also need a surface drain.
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