How do I prevent texture distortion when the UV islands extend outside of the UV Grid?

I UV unwrapped a model in Blender.  It's meant to be a tiled wall so I scaled the texture to reflect the real-world size. When I do this, the size of the UV islands increases so it extends outside of the UV Grid. It looks fine in Blender but when I import it into Substance Painter, I get texture distortion. Does anyone know how to fix this without compromising the texture scale?