Storm-water pipe grading and surface-drain location issue

I built with Eden Brae Homes and "Pipeworx Plumbing & Drainage" was their sub-contractor; I see couple of issues in their - Stormwater drain pipelines and surface drains.

1) As in below picture, 100mm Stormwater-drain pipeline is holding around 70mm(high) of water in it all the times - at-least in couple of places visible through the surface-drains.

Pipeworx is giving excuses like my land is flat and they couldn't grade the pipe. Whereas, in the building contract - the builder is supposed to provide required import/export of spoil needed and also storm-water system.




2) The second issue, the surface-drains in my backyard that they installed is very closer to house slab(first one is 30cm and second one 40 cm closer to slab - picture below);
If we grade the backyard to drain the stormwater into this, then it will keep the slab wet and moisture(negative grading) and cause structural issues later.

These surface drain locations installed cause more damage rather than benefit and seems to be against BCA guidelines on grading the soil away from the slab.




Both Eden Brae and Pipeworx are just beating around the bush - without telling how/whether they fix these problems.
Another contractor commented this as a poor quality and sub-standard work.

It will be really helpful to know - how to handle these kind of issues with builders and their contractors.

I have to assume that you have not had a building consultant during your build.

Stormwater pipes your size require a minimum1:100 slope for compliance. If the work has been wrongly certified, contact the DFT.

The heights can be changed to suit later landscaping. This is normal.

Thanks SaveH2O.

By seeing this amount of standing water in the pipe(70mm standing water in 100mm pipe) , I doubt they would have graded with 1:100 ratio.
Is there a way to verify this by any tools before I raise this issue further.


My concern about the close proximity of surface drain near slab is because - If I bring the stormwater falling in 3.7meter wide backyard to to surface drain near slab, then it will be become negative grading which adds more moisture to the slab.

Also, this backyard is in southwest direction where there is no direct sunlight for more than 6months in a year and it is taking atleast 3 weeks to dry if there is a mediam rain.

- BCA standards(3.1.2.3 Surface water drainage) says to grade the water away from the slab - 5 percent for first 1 meter; Thats why I think Builder should have placed this surface-drain at-least 1 meter away from the slab.

It would cost nearly $300 to put a cctv camera down the stormwater pipes to get a video as proof of pooling. You could just use a phone video to show the water and then show putting a dry stick in and out to show the depth of water inside. You don't need anything fancy.

70mm of standing water is bad workmanship and it is not compliant. Ask the surveyor if he was given a Certificate Of Compliance.

Inadequate slope compromises the pipe's drainage capacity.

Drains are often put in paths, 300mm from the slab is close but I am not aware of any regs prohibiting it.

The regs require a slope away from the house but drainage is also very important, it is best not to let water flow off the path and pool next to the path. The current BCA and AS regs re surface drainage away from the house are inadequate in part in that they don't place importance on drainage, only slope. Do the plans detail the stormwater pipes?

Thank you for your insight.

I spoke with builder and Pipeworx today.

Pipeworx will be visiting the site for inspection on Thursday. For grading - they said No to me in phone and then Yes in front of builder - need to see how it goes on Thursday.


For surface-drain location in backyard, builder also said the same as you that they no need to provide it. And, they suggested to install multiple agg-pipes and connect it to the bottom of surface drain-pipe.

I need to understand the feasibility and depends on it,
- either do agg-lines and connect it to existing surface-drain
- or hire someone to add an elbow /t-joint to move that surface drain away from the slab and grade the soil towards the drain(like 1 meter away).

Don't take any nonsense from the plumbers....they have done non compliant work and treated you like a mushroom by keeping you in the dark and feeding you bs. With plumbing, it is out of sight, out of mind. It is however possible that the standing water is the result of an obstruction but a depth of 70 mm makes this unlikely. Regardless, I always recommend that new home owners have an independent cctv camera inspection of all stormwater and drain pipes pre handover.

The site should be sloped away from the slab during construction and at handover. The site must have good drainage.

What are your landscaping plans next to the house? What you do depends on the answer to this question.

Are you going to have an impermeable perimeter path? If so, it is best practice to direct the water to a drain without it flowing off the path. There are a few ways to do this which a good concretor will know.

If you don't have an impermeable surface, you may well need ag drains. Do you know the soil classification?