Modify depth of stormwater pit

indo26slate · Feb 22, 2021 1:28 pm

Hi all,

I am currently planning for (designing) a ground/surface level drainage design at my property.

I am based in Brisbane.

My property is almost flat, with very limited fall to the street (discharge point). There are no other stormwater services available to discharge to.

It's a 46 meter distance. There is only 420mm fall to the street gutter.

My design will be using a combination of drains, pipes and stormwater pits, to try to pick up the surface water and achieve the fall to the street.

At the first catchment point (upstream) I'm intending to use a wide stormwater pit, but I don't want to have an excessively deep pit.
Note: I want to reduce the amount of water retention inside the pits.

Infact if I could find a low profile drain which is wide, I would prefer that instead of a pit, but I can't find one (I don't think they exist).

Is there any good way (but an easy way) to reduce the depth of a stormwater pit?

Take for example the pit shown in the attached photo.
[img:2dm4hwdr]https://forum.homeone.com.au/u/76977_1613978187.jpg[/img:2dm4hwdr]

Noname · Feb 22, 2021 2:48 pm

You mean something like this
https://www.everhard.com.au/category/dr ... nel-grate/

indo26slate · Feb 22, 2021 6:18 pm

I've tried to attach a photo (which is essential to my question in this post). It doesn't appear anywhere. Can anyone see the image attached?

Noname · Feb 23, 2021 7:37 am

indo26slate · Feb 23, 2021 10:19 pm

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Noname · Feb 24, 2021 7:49 am

The do come smaller AFAIK, which translates to shallower. Though that also translates to less capacity. Given the level of rainfall during some of the storms Brisbane has seen in the last decade, I'd question whether getting a smaller capacity pit is a good idea.

Is it just that you don't want to dig Or is there another driver? If it's just aesthetics, id move on and start digging. There are tools that can be useful when needing to dig holes for these pits (like a post hole digger/auger) that will take some of the effort out of it. You can hire them from Coates.

indo26slate · Feb 24, 2021 9:19 am

Noname

The do come smaller AFAIK, which translates to shallower. Though that also translates to less capacity. Given the level of rainfall during some of the storms Brisbane has seen in the last decade, I'd question whether getting a smaller capacity pit is a good idea.

Is it just that you don't want to dig Or is there another driver? If it's just aesthetics, id move on and start digging. There are tools that can be useful when needing to dig holes for these pits (like a post hole digger/auger) that will take some of the effort out of it. You can hire them from Coates.

The reason for wanting a shallower pit is because I want to minimize the volume of residual water staying in the pit after a rain event is over.

indo26slate · Feb 24, 2021 9:26 am

The reason for wanting a shallower pit is because I want to minimize the volume of residual water staying in the pit after a rain event is over.[/quote]

And I'm guessing you might be wondering then why use a pit in the first place?

Originally I wanted to use a drain but since I have a very small amount of fall to the street over a long run, I needed to find the shallowest drain to "save" as much drop as possible when connecting into the 90mm pipe. I found by tapping into the side wall of the pit for the pipe connection I was able to "save" drop space.

I also wanted a very wide drain (i.e. 560mm wide X 560mm long) to make the task of grading the land into the drain easier (aiming for a bigger target), but drains don't come in such a size as far as I could find.

Noname · Feb 24, 2021 10:48 am

id imagine that with the wide pits, evaporation will take care of the residual water relatively quickly in Brisbane weather. if they are too shallow, then they would not operate as per design, which is to catch and hold silt from entering the main system.

I think you're over thinking the actual design of the products rather than thinking about how to best to install the designed and tested products into your landscape.

indo26slate · Feb 24, 2021 6:05 pm

Ok. Thanks.

moudzj · Mar 07, 2021 2:42 pm

Standard practice is to fill with concrete to the bottom of the outlet pipe to avoid any stagnant water, which is absolutely undesirable.

Pulse · Mar 07, 2021 8:16 pm

second that just fill with concrete