Home buyers should discuss this issue with their insurers to determine appropriate options (do nothing, replace in part or replace in whole). Insurance companies have massive data banks in their files on all kinds of failures, by product, by region. Our advice is to use their expertise to provide you with guideance as to what to do about it. Plumbing contractors can also be a good source of information since they see a lot of this product and can offer their expertise on the issue.
Sometimes the risk is manageable. For example, if most of the plumbing is in a crawspace, then if a water leak did occur, then the damage to interior structures and finishes will be minor.
In other circumstances, when only a limited budget is available, it may be appropriate to replace in part the Poly B plumbing with modern plastic piping (called PEX), say when there is an upper level. In these circumstances the lower level and crawlspace can remain as is with Poly B.
As a potential buyer of the home with Poly B plumbing, be sure to do your homework and know in advance if there will be any financial impact to you. Best case scenario is a minor cost increase in your insurance policy. Worst case would be if the insurer will not cover associated water damage to the house, and total Poly B plumbing replacement is adviseable.