Plumbing a Solar Pool Heater
Water goes in the bottom of the solar pool heating collector bank. Air in water wants to rise so this way the air flushes naturally up to the highest point where water leaves the solar collector system. Water can then flush the air down the return pipe back to the pool. When plumbing a solar heater that is more than 2 storeys above pool level we pay attention to the way water flushes that air bubble down the return pipe. We want to minimize the height of the column of air that is developed.
When plumbing a solar heater we have to think about air. If we trap air we have a hot spot caused by no flow. In a conventionally oriented solar pool heating collector array we have to tilt the entire bank so there is a defined high point where air can rise up to naturally because if we slope it the wrong way look what happens
If the roof is flat meaning not pitched toward the sun we still have to pay attention to high points and air releases. A flat roof will be sloped for drainage sometimes in complex ways. Header manifolds must slope such that water can exit at the high points. The feed side isn't as important but should still follow the same rule in reverse. Water goes in at the low corner. You want water to drain out of the lower manifolds by gravity so you can winterize the system without having to go on the roof.
We also have to pay attention to gravity. If we let the water out at an elevation lower than the high point water will not fill the upper collector bank