Does anyone know if a solar drain valve is good?

Ordinary solar water outlets are at the bottom, and there will be some water between the drain valve and the water outlet. Since the amount of water is very small, solar energy will emit heat, so it generally will not freeze. , but insulation must be provided to reduce the risk of heat loss. Real drain type solar does not require a drain valve. The water inlet and outlet are at the top of the water tank. After draining, there is absolutely no water in the pipe. the life of the water tank is significantly extended.