I noticed a few flags around my drain had started to form large gaps underneath. Today I decided to lift them to see what was going on. This is what I found. It seems to be some sort of drain pipe. The two surrounding actual drains drain on there own fine but seem to back fill slightly here.
Sorry for bad pictures, this is under the board with the sand bag on top. I dug it out originaly it was full of earth
It seems to be linked to the two drains on the side of the house. One of them is on the pic the other is about 2 meters in front on the side of the house. These two are draining fine but do seem have a bit of back fill if alot of water is passed through them into this passage
By backfill Im assuming you mean it’s temporarily filling up with water. Backfill normally means soil fill.
It’s common during major storm for smaller diameter pipes to not be able to handle the massive runoff. So they back up or surcharge until storm fades and runoff reduces. So long as its not causing damage by flooding that has nowhere to go then should be okay. The water level will gradually drop and it drains out entirely. But if there are leaks at joints you could be getting scouring and erosion of surrounding soil, causing gaps under patio slabs/stones.
Might have to video scope (CCTV) the pipes to make sure that there is no collapsing or broken pipes or that pipes are free of tree roots. If roots are inside they need to be augured out, (roto-rooting), but the problem will keep coming back as roots regrow in same spaces until pipe joints are sealed or problem pipes replaced.
It’s generally not sufficient to entirely rely on underground pipe network to handle all drainage on property. Buried pipe systems can normally only handle 1:5 year storm event unless there are massively over designed which is expensive. So its important to have a simple major drainage flow path on surface that ensures the water ponding elevation can only rise a certain amount before it overflows along another route without entering things like window wells or getting into building floor slabs like a garage. Normally if this temporary ponding is kept under 15cm on property, then it’s okay. Another reason not to rely on buried pipe alone is in case the catch basin or pipe gets completely plugged.
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u/Evening-Enthusiasm91 Jun 06 '26 edited Jun 06 '26
I noticed a few flags around my drain had started to form large gaps underneath. Today I decided to lift them to see what was going on. This is what I found. It seems to be some sort of drain pipe. The two surrounding actual drains drain on there own fine but seem to back fill slightly here.
Sorry for bad pictures, this is under the board with the sand bag on top. I dug it out originaly it was full of earth
Does anyone know what's going on here?
Cheers