What is this round grate drain for?

[Ryanoo]

Hi Guys. I need some advice on this. I just wondered what this drain for. Is this for sewer or stormwater purpose? This drain is just located next to the wall at the backyard, behind my kitchen.  Thanks in advance

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There is another inspection point 2 meters away from that. I unscrewed it, and it is clean inside. I just hosed the grate drain and then I found the water flow through the inspection point after a couple of seconds. When I just turned on the tap in the kitchen, I could hear the water flowing sound if move close to the inspection point. So I am so confused. I wanted to know what this is because i would like to find a stormwater drain point for my paving area. So, yeah. 

More pics:

[JacobZ]

Hi @Ryanoo,

Thank you for your question.

I would suggest that this is an inspection outlet or overflow for stormwater. It is extremely unlikely that you would have an exposed pipe connecting to the sewer, but there is a very simple way to work it out. Smell it, if it's a sewer pipe, you'll know.

Is there a reason for the question? or just curiosity?

Let me know.

Jacob

[Ryanoo]

Thanks Jacob. I just added more info in my question. Would you be able to check the question again and give me your thoughts? Appreciate it. 

Ryan

[MitchellMc]

Hi @Ryanoo,

If your sink water runs through this pipe, it's likely a sewage pipe if plumbed correctly. The outlet is for inspection and access purposes and could also be a drain waste vent that allows the sewer pipe to maintain neutral air pressure. The only thing that should be running through your stormwater pipes is stormwater.

Please let me know if you have any questions.

Mitchell