GrowCNanswered grow question 2 years ago Laying out in the sun is safe. Put something heavy on one end and roll it out and put something heavy on the other end. Let it get hot in the sun. Then, keeping it unrolled, bring it in out of the sun so it can cool and help lock in the straightness. You can also submerge the tubing in hot water or place it in a warm (NOT hot) oven to soften the plastic slightly.