nasty job on waste pipe inspection hole

[Sup9]

There is a 3.5x4cm opening cut on the waste pipe, the opening is opposite to the kitchen drain pipe which I think the previous owner used this opening to unblock the kitchen drain pipe. But the cut was square and they used denso tape to seal it.
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For the time being I think this opening is quite handy because the kitchen drain pipe got blocked quite often. Can I make this opening proper inspection/access hole by weld/seal with sealant and adding this access plug?
https://www.screwfix.com/p/floplast-abs-access-plugs-white-40mm-5-pack/23322

Or is it possible to have a plumber to replace this whole section of 3-way pipe with maybe a 4-way, so I can still access to the kitchen pipe if blocked? If I'm going this route I'll consider to have the kitchen drain pipe replaced too to get rid of all the issues at once but I think it might be quite expensive to get it done?

 

[Sup9]

would any of these 40mm boss work if I put enough glue/sealant at the base to attached it and seal with the waste pipe?

https://www.amazon.co.uk/Plumb-Pak-...coding=UTF8&psc=1&refRID=CPWW5RTH8TM96HYXG82M

https://www.amazon.co.uk/Mechanical...coding=UTF8&psc=1&refRID=CPWW5RTH8TM96HYXG82M

https://www.amazon.co.uk/McAlpine-B...coding=UTF8&psc=1&refRID=CPWW5RTH8TM96HYXG82M

 

[Newboy]

Can I make this opening proper inspection/access hole by weld/seal with sealant and adding this access plug?

No

would any of these 40mm boss work if I put enough glue/sealant at the base to attached it and seal with the waste pipe?

Very unlikely that any of those would cover the existing hole or adhere to the pipe.

Get the section cut out and replaced. At the same time replace the kitchen waste pipework and allow for clearing access from the other end.

If that's a stack pipe then you potentially have foul waste and sewer gases exiting into the area.

 

[Hugh Jaleak]

As above. Section needs cutting out and replacing. If the kitchen waste keeps blocking, then either the pipework isn't correctly installed, or someone is putting something they shouldn't be, down the sink...

 

[Sup9]

Thanks for the replies. I bought a Nilfisk pipe cleaner see if I can have the kitchen pipe sorted and getting a quote for replacing the section.