Entran hydronic heat tubing was used in many houses in the late eighties and early nineties. It was manufactured by Goodyear and became the subject around 2001 of a national class action suit. It was determined that the tubing used could not hold up to the demands of a hydronic heat system, becoming brittle, leaking, and eventually failing altogether.
Unfortunately, your blogger used this very same product in 1991 retrofitting an existing all-electric house adding a gas boiler and stapling up the ENTRAN tubing from the crawl space below. Worked fine for 20 years until one month ago when half the system sprang a leak and had to be replaced (Yes, even contractors have issues with their homes).
The new product, Onix tubing, by Watts Radiant, is superior in all ways and has an excellent field record. Perhaps the remainder of my system will sustain itself until warmer months when replacement will be completed.
As contractors we have been involved in ENTRAN replacement commercially. It is never a pleasant experience or an inexpensive one. The staple up described above is most affordable and does not disrupt the living space at all (except for lack of heat in the winter, yikes!). Much more expensive is tubing laid in concrete or under brick on sand flooring. Both of these remediations require extensive disruption to the living space and will often require homeowners to move off the premises.
Radiant heating is a joy to live with: silent, constant, and takes up no floor space. But always a proper appreciation of the products available and a qualified and experienced and licensed installer are key to a good job.