Pool valves can be pretty confusing to most swimming pool owners. We have put together a series of articles that illustrate how to set the valves on the typical backward pool/spa combo.
Every pool is different and these articles are designed as a general guide. As always, if you are not sure of what you are doing, get a pool professional involved who can answer any questions you have and give you professional onsite advice.
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In normal mode, on the intake side, the spa drain is closed and the pool drain and skimmers are open.
If the spa drain is open, then you risk draining the spa. This is especially true if the spa is elevated because when the pumps turn off, it will gravity drain into the pool.
On the return side, the spa jets are closed and the pool returns and water feature are open.
IMPORTANT: You cannot operate the pool if all the valves on the intake side or all the valves on the return side are closed. You run the risk of equipment damage and human injury if you do.