Winterizing a solar water pump

If it shuts down for winter

1. Drain surface pumps completely and store them indoors if possible.
2. Drain above-ground pipe and leave low-point drains open.
3. A submersible pump below the frost line in a well is safe left in place; drain the pipe above ground.
4. Disconnect the array from the controller, or switch the controller off, so the pump does not try to run dry.
5. Bring batteries indoors or keep them where they stay above their minimum storage temperature.

If it runs all winter

• Bury every line below your local frost depth, and insulate where a pipe comes out of the ground.
• Use a pitless adapter at the well so the line leaves the casing below ground.
• Let above-ground pipe drain back to the well after each pumping cycle. A check valve at the pump stops this, so drain-back designs use a weep hole or a drain valve below the frost line instead.
• Insulate or bury storage tanks, or keep them large enough that the volume does not freeze through.
• Use troughs with heaters, insulated lids, or a flow-through overflow so water keeps moving.
• Size the array for the darkest month and set the mount to a steeper winter tilt, which also helps shed snow.

Batteries in the cold

LiFePO4 cells can discharge in the cold, but most makers prohibit charging below 32F (0C). A battery in an unheated pump house in the northern states will spend weeks unable to charge without protection. Choose a battery with low-temperature charge protection at minimum, or a self-heating model, and insulate its box.