I have been running a 2 speed pump for 7 years now. Wow what a difference! I bought the motor from Perry's Pool Pump in Arizona with a shaft seal to put on my old housing. This is a 3/4HP Low /2HP high motor. On high into my 1.5" return piping the restriction is high, and the power meter really spins. On 3/4 HP I get about 1/2 the flow, and the power meter rotation rate slightly increases when turning on the pump.

My setup will prime on low speed, but it might take a minute or two. This happens when I get a piece of dirt, or a leaf on the pump basket O-ring. Otherwise there is no need to prime other than when I clean the basket. I installed a weatherproof dual switch on the house wall right next to the pump. It has low/High and off/on right there for convenience.

The other issue seldom mentioned is low speed with a salt system. First we must have enough flow on low speed to make the salt system flow switch. Second, since a SWG cell produces hydrogen gas, when the pump is on Low, there might be a buildup of gas in the return lines. This happened to me. The buildup was such that after about 4 hours SWG run time, the water return lines were full of gas to the point that the water flow switch tripped off. Turning the pump on high cleared the problem after lots of bubble gurgling from the farthest away water return jets.

One fix for the hydrogen gas issue is to have the return lines rising slightly underground toward the pool, but never sloping down. Of course keeping the pump on High fixes the issue, as would a 2 minute burst of High speed every 4 hours. I picked a third way. My pool has 5 water return jets, and the farthest away from the pump three jets got plugged up from gas. The solution was to put rubber stopper corks over the two closest return jets. Now I had enough water flow in the remaining jets to keep the gas from building up.

For those that don't believe those bubbles are hydrogen, when running pump on low speed we get big bubbles coming from the return jets. Then turn off the SWG cell, and in 60 seconds the bubbles go away. The bubbles will return when turning the SWG back on. Take a BBQ grill charcoal lighter, and you can ignite the bubbles in loud snaps. Be careful though since the return line might be full of gas, and the filter too....Boom!

Jimmy C