Sorry, my post on the weekend didn't load.
The pipe you have is old earthenware agi-drain.
The pipe was laid with gaps between the joints to allow ground water into the pipe.
It looks like it was buried in 20mm rock, which is normal.
It may also be a run-off drain from a septic tank also.
Do you or was there ever a septic tank installed at the property?
There's no point sealing up a joint, because there will be a gap between each section of pipe.
Where abouts are you located?
We have had an awful amount of rainfall for the last couple of months.
Does the drain look fairly clean of roots and debris on the inside, it may still be a functioning drain