So we glued together a bunch of 4" PVC for our bottom drains this weekend. Essentially all glued joints failed. We think it's because the schedule 40 pipe diameter is just a little too small. Moving on. We decided to buy some 4" flex PVC to try to simplify things. A 50' roll is pretty reasonable from the online retailer we use; however, they are out of 4" pipe and the distributor is not going to have stock available until the spring. We have plenty of 3" flex PVC on hand. Would it be too much of a compromise to use 3" flex PVC instead of standard 4" PVC?