Here are a dozen or more articles with pictures showing Kitec fittings, including a link on page one to an attorney representing home owners on this issue.
However in light of the class action settlement your options might be limited, I am not an attorney and cannot advise you on that aspect.
There are companies in the business of replacing the entire Kitec system tubing and all. This is too big an issue to discuss just one aspect at time, you will need to come up to speed on the wide range of issues related to Kitec...looking those links over will be the most complete approach.
Notice these fittings, apparently both types have been termed 'ticking time bombs' You will not know if they are going to fail until they leak...
If I were in your position, I would leave the underflow tubing in place. and replace all of the other Kitec tubing and fittings in the house.
If by chance there were a coupling in the underfloor Kitec tubing I would cap that circuit off and install hydronic base board heat in that room.CLICK HERE
to read about the actual tube construction... continuous lengths should be good under the floor for a very long time.