Methods and systems for solar water heating are provided herein. A modular pipe system for a solar water heater is provided in one embodiment. The system includes a plurality of first manifolds which are interchangeably connectable to any other first manifold. The system also includes a plurality of second manifolds which are interchangeably connectable to any other second manifold. The system further includes a plurality of pipe panels which are interchangeably connectable to any other panel, any first manifold, and any second manifold. Connecting the first manifolds and the second manifolds end to end expands the system along a first axis, and connecting a plurality of panels expands the system along a second axis perpendicular to the first axis.