Kitchen Piping Tundish problem

[andycorleone]

For over a week the kitchen sink is leaking water from what I think is called tundish ( I thought is was called overflow but little google search maybe pointed me to the right name)
my guess is the pipe is slightly blocked because this only happens when there is a huge amount of water coming from above (for example when I fully fill the sink and then i take out the drain plug and all the water goes down in one go) Usually during normal operation is fine.
How can I solve this?
I was thinking in buying some Sink Drain Unblocker from the supermarket. to fully clean the drain, is this a good idea? as I said is not blocked maybe only 50%. I already check all the pipes from above they look Ok inside. so the only one that I wasn’t able to check was the ones from picture #2

 

[Gasmk1]

Probably needs repiping tun dish is in wrong position, what is the tun dish for water heater or something else or overflow from toilet or similar

 

[andycorleone]

Hi, this is overflow from kitchen sink. please see image attached

 

[ShaunCorbs]

It’s from a pressure relief 1st picture middle top the mlcp pipe / fitting

Is it an island sink or boil tap ?

 

[Basher]

What I'm reading is not water entering the tundish from above (ie not a relief acting) - it's waste water from the sinks backing up and overflowing from the tundish as the drain capacity has become reduced due to a partial blockage.

Given there's a dishwasher or washing machine connected on the left, there could be a build up of sludge in the bottom near-horizontal run shown highlighted in the second picture.

There seems to be a rodding cap on the right hand end which could be removed and a snake poked down there!
If you've checked the other pipes (especially the "U bend" /trap) and they are clear, I think the pipe highlighted could be the culprit. Getting drain cleaner into it might be more difficult than physically clearing it!

 

[andycorleone]

@Basher I think you are right. the problem is the build of sludge in the near-horizontal pipe highlighted. what is the best way to clean this? maybe a Flexible Rod Auger?

 

[Basher]

@Basher I think you are right. the problem is the build of sludge in the near-horizontal pipe highlighted. what is the best way to clean this? maybe a Flexible Rod Auger?

Yes. There's not much room, but a springy thing poked down that pipe might help!
otherwise try drain unblocker, but you would need enough to over fill the "U bend" so that the chemical flowed into that horizontal run of pipe.