What size agi pipe for backyard drainage?

[amanda5]

Hi,

We need to install Aggy pipe to drain a small sunken backyard area, 6m by 5m in size. Currently, a lot of water pools when it rains heavily and it takes quite a while to drain away. We live in Caulfield North and I'm told we are built on land that was once a swamp, so presumably this is the reason why.

We are trying to decide which size Aggy pipe (or smiliar product) to use. We think 65 mm in diameter, but are not sure if we need to go to the 100mm diameter pipe to be safe.

The water from the Aggy pipe will drain into a sump that will pump up into a storm water drain.

Thanks for the help

Amanda

[EricL]

Hello @amanda5 

Welcome to the Bunnings Workshop community. It's wonderful to have you join us, and thank you for sharing your question about drainpipes.

Using a 65mm drain coil is good and it will be able to handle a reasonable amount of rain. But should you have a large continuous downpour a Vinidex 100mm x 20m Socked Slotted Draincoil would be more appropriate. Both drain coils will be able to do the job except that the 100mm will be able to handle a larger volume of water. That large rainstorm might not happen any time soon, but it's always best to be prepared for such an event.

Let me call on experienced members @TedBear and @Dave-1 for their recommendations.

If you have any other questions we can help with, please let us know.

Eric

[Dave-1]

Good Morning @amanda5 

Id like to add a welcome also I found the community awhile back and its kind of become a place to listen to answers.

As @EricL  suggests I would go with the 100mm sock pipe for sure. This is what I installed in one of my projects to stop water ingress into my garage. 

Fixing water ingress issues in garage 

So Sock plus gravel chanel worked wonders for me. I have an area that is the low point of part of the yard and also has shale/clay underneath so water would generally pool until it seeps away. Once I had the sock pipe installed like a snake and back filled with gravel then paved over I waited for some rain, well we had an absolute downpour and of course I had to go look, not a puddle! Shock and surprise was the only way I could describe it.

Definently a believer that the bigger and stronger 100mm piping is a better option for drainage. If I had gone smaller then the downpour wouldnt have drained so nicely.

I would have a long slow curve trench like a snake to the lowest collection point. Also would suggest to have an inspection point at either end so you can clean the pipe out if needed. Backfill the trench to the top of the agipipe and it will give it the best chance of drainage.

Dave

[TheHandySqirrel]

I have so far used the 65mm agi pipe in my projects and found there is a shortage of affordable adapters to the standard 90mm stormwater pipe. 

For that reason I agree to go with 100mm as you’re more likely to find adapters. 

[Taleya]

How did you set up the inspection points?

[EricL]

Hello @Taleya 

Let me tag @amanda5 to make them aware of your question.

Thanks for sharing your question about inspection points. Are you referring to Holman 90mm 90° Female And Female PVC Stormwater Junction or Everhard 325mm Series 300 Shallow Stormwater Pit. Generally speaking, you can place an inspection "T" in between the length of your agi drainpipe. So, if it was 20m long, you can split it in half and place the "T" in the middle. 

The drain pit on the other hand is often placed when you have two agi pipes coming together and there is a low area in your yard. This acts as an inspection point and additional drain to your yard.

If you have any other questions we can help with, please let us know.

Eric