A fiberglass pool takes time to build, install and finish. How Long to Install a Fiberglass Pool? Lets just ease your mind or frustrate you all at once, not sure which one it will be for you. It takes WEEKS to install a fiberglass pool, vinyl liner pool or concrete pool. Fiberglass construction will go much quicker than others, but it still takes weeks for the full project. Factor in the basic steps when getting a pool :: Permitting for the pool. Engineering for the soils (rarely, but can be necessary)