My spa has 4 returns, but the water barely trickles out of 2 and literally jets out of the other two. At first I thought they might be clogged, so I drained the spa and got in there with a flashlight and couldn't see any obstructions (they don't even have the "jets" - they're just bare pipe). Thinking perhaps there might be an obstruction out of view I tried feeding the garden hose into each at full pressure (and we have really high pressure). Nothing happened. The returns accepted all of the 3/4" hose output, which just came out the other returns. I'm thinking either the pump is undersized or that not having the jets to restrict the flow is causing most of the output to go out the two returns. The pressure on the filter bumps up two pounds when I direct the output to the spa, so that it doesn't increase more is also making me think it's not a clog.
Anybody have other ideas?