water drainage

What is the name of your state? What is the name of your state? Massachusetts
I am the 'upstream' resident of anunderground drain pipe {12''] behind my and 2 other homes.Both homes have new occupants. Because the catch basin behind my home [the main collector ]backed up caused $10K plus damage to my lower floorand appeared to exhibit some obstruction after an unusual heavy [8'' in 12 hour rain], I had the approximately 500' of pipe and 2 catchbasin and 2 manholes flushed and cleaned [after notify and receiving approval for accass and saying prior occupent had shared cost]. Furthest downstream resident paid 1/3 of cost[$250], middle resident refused,saying realtor did not tell him about drains. I have a developer provided plot plan that showed easement behind 3 lots.
Should easement be on other 2 titles or on my title? Are downstream lot owners resposible to keep drain/12'' pipe open? How do I get legal assurance for shared costs? Am I liable for all cost or is this a shared cost? Expect to sell within 5 years after 38 years and need advice aboutmaking sure next owner is on sound grounds[other homes are in 750 + range]

[HomeGuru]

An easement agreement affecting property should be recorded on those affected properties.
Your issues are too complicated for this forum. You need to hire an attorney that can review the title reports, survey maps, review the local building and zoning codes etc.