Why is there gas in the solar hot water pipe and even no hot water comes out?

If there is air in the hot water sewer pipe or the sewer pipe is kinked, the water will not flow easily or the water will not flow . If you want to drain the water, you must first have water in the water tank, then empty the air into the sewer pipe and try to avoid detours in the sewer pipe. Additionally, when the water in the water tank is completely used up, air will enter the hot water pipe and will need to be emptied the next time you use it.