Kitchen sink pipes - leaks and general questions!

[NewHouseNoMoney]

The kitchen sink overflow (red arrow) leaks. The tube (red curve) is also unbelievably smelly and has gunge in it. I’ve taken the tube off the connector and poured all sorts of products in it to try and clean it but it hasn’t worked. It doesn’t look as if I can buy a new tube because it’s all connected to the rest of the piping. Is there a way to seal the connection at the top of the tube?

I have also read @pigletjohn saying that the dishwater waste tube (blue arrow) should be higher than the base of the sink. Is this right?

Finally, there is staining at the yellow arrows. I’m not sure if this is related to the overflow leak but I would be grateful for any thoughts.

Ideally thoughts that do not cost me much money! 😅 Thank you.

Actually, it may be the case that the leak is coming from where the overflow fitting actually joins the sink (new red arrow).

As you can tell, this is all new to me!

Stand back and take a wider pic to include what's under the sink.

Put a bucket underneath to catch the water when you absently turn on a tap to wash stuff in the sink while working.

The overflow probably clamps onto the sink with a screw that you can access from inside the sink. Undo and clean that joint and reassemble tightly. There is probably a rubber sealing ring. Is it perished?

Next the big plastic ring. Unscrew, clean, replace, Use rubber gloves to turn the ring. The flexible hose looks like it has a dip that will hold stagnant water. Reroute it so it is constantly running downhill.

Is PigletJohn right?

What a strange question.

The flexible waste hose from the dwr must loop up to touch the bottom of the worktop to prevent waste water from the sink running down it into the dwr.

You can use Soda Crystals to clean the sludge. Not caustic soda.

Why is there sludge? Has oil or fat got into the sink?

Buy a set of screwdrivers and a pair of waterpump pliers before you start.

Here are some sink wastes including a new flexible tube

www.screwfix.com/c/heating-plumbing/wastes/cat831612?wastelocationtype=sink&cm_sp=managedredirect--plumbing--sinkwaste#_=p

And some new sink trap kits. Mcalpine is a good brand.
www.screwfix.com/c/heating-plumbing/traps/cat831610?trapapplication=sink%7Csink_basin&cm_sp=managedredirect--plumbing--sinktrap#_=p

@PigletJohn You are a star! I know you are always right I meant more along the lines of, is my interpretation that this tube needs to be higher, right?!

I am just about to start work but will do/look at everything you say later. And I will post a wider view photo.

As for the sludge - yes I imagine it’ll be oil or fat - but not from us m’lord! It absolutely PONGS!

I am very grateful for your time and wisdom. If only I could have you on speed dial!

The flexible hose looks like it has a dip that will hold stagnant water. Reroute it so it is constantly running downhill.

Aha! Yes it does hold stagnant water. But I thought this was part of its design (like the U bend).