I would back out of the escrow under these circumstances. Even if your unit’s PBT pipe has been replaced, it is likely NOT replaced under the slab. More owners DID NOT use their proceeds from the class-action suit proceeds dispersed in the early/mid nineties to replace their PBT plumbing than did. Buying in this complex sounds like a future headache and money drain to me – as well as unsafe. I’m suprised financing is currently available for it.
Congratulations for having the sense to carefully read the documents provided you in escrow! So many buyers of these affected units (condos AND SFR’s) become enamored of the property prior to closing on it and don’t read the fine print and then sign off their contingencies. These two items had to have been well-known by the seller and should have also been listed in your Transfer Disclosure Statement, provided to you upon your accepted offer. If this info was not and your sellers were NOT REO lenders, then they were trying to hide these material facts from a potential buyer.
There are many properties currently on the market and you will find another one to buy.