Waste water drain query

[Rollerball]

The waste pipe that takes the water from my kitchen sink naturally exits via a hole in my house and is then diverted via a white waste pipe into a vertical open round drain that's about 7 or so inches in diameter(with a plastic grill on top). This drain then leads to the main drain/sewerage system.

I just noticed that this open round drain was overflowing and had to dig around with my hand to release all of the grey gunk that was blocking it up. I got out what I could.

It's no longer overflowing (even with plenty of water flowing into it) and the water level is much lower but I notice that there is now a set low "level" of water that is always present. I'm assuming that this is a water trap to prevent any smells, etc from coming back up via via the main drain. Is that correct?

Or shouldn't there be any water in there at all?

 

[nickjb]

You are correct. That's the trap level. Normally about 6 inches down. If the waste water is going away and that level isn't changing then all is right.

 

[Rollerball]

Many thanks, that's good to know.