There was another thread here the I read (from quite some time ago) about adding a makeup water line directly to the pool plumbing as opposed to using a hose. In my case, I have a hard line already plumbed from the house to the pool for filling, it was installed with the pool and there is a pressure vacuum breaker to prevent backflow from the pool to the city water supply the same as is required for our irrigation system.
The problem is that it is leaking and now is the time to make some changes as I am working on a Raspberry Pi/Arduino pool system of sorts which will include monitoring the pool level and adding water via a sprinkler valve when necessary.
In my case the easiest way would be to plumb the makeup line directly into the main return line of the pool. My question is would I need to install a backflow device on the filter side of my connection to prevent water that I am adding from pushing backwards into my filter system? My Pi will be monitoring my pump and will prevent the sprinkler valve from operating while the pump is in use, but when everything is off and I want to add water, I am worried (maybe without reason) that water from my makeup line (standard house pressure of about 65psi) will actually force water backwards through my system.
Any input would be greatly appreciated.