If the KO responded in a reasonable amount of time asking for more information (price and time), is that enough information provided to the KTR to inform them not to proceed with the work as is. Was a partial Suspension of Work needed to go along with the RFI response?
But basically I have to side with Prime and the Subcontractor here. It is really immaterial how much time it took the contracting officer (KO) to respond to the RFI (reasonable amount or unreasonable amount). Without a formal suspension of work order or some other type of communication from the contracting officer through the prime to the sub indicating the Government did not want work to proceed until it decided what size pipe to use; the prime and subcontractor had no authority to or contractual requirement to unilaterally stop work and wait for the government to make its decision.
The answer above is based on the assumption that completing the project using ½ inch pipe will not result in any material defect or unsafe condition and that the completed project will meet the minimal needs of the government and the original contract quality standards. We assume the ¾ inch pipe is only “better”. If this is not the case or right assumption, there are other clauses, e.g. FAR 52.236-21 Specifications and Drawings for Construction (Feb 1997), which might have put a requirement on the contractor to notify the contracting officer prior to commencing. But again, we didn’t have those facts.