This is it and it seems to only be residential pools.
(4) Pool pump motors shall not be split-phase, shaded-pole, or capacitor start-induction run types. Residential pool pumps and pool pump motors with a total horsepower of 1 HP or more shall have the capability of operating at two or more speeds with a low speed having a rotation rate that is no more than one-half of the motor's maximum rotation rate. Residential pool pump motor controls shall have the capability of operating the pool pump at a minimum of two speeds. The default circulation speed shall be the residential filtration speed, with a higher speed override capability being for a temporary period not to exceed one normal cycle or 120 minutes, whichever is less; except that circulation speed for solar pool heating systems shall be permitted to run at higher speeds during periods of usable solar heat gain.
I am still not sure how this saves energy over just running the regular pump for one turn over and shutting it off, which is what most pool timers do.
Mine runs about 6 - 6.5 hours unless the solar heat is on and then it shuts off when I am not getting any solar gain (after the base cycle).
If I had a 2 speed pump I would run it at low speed when the solars were working and after I had the required turnover, just the opposite of the law.
You don't need much water moving if you are just extracting heat from the collectors.
Politicians always want to fix something that ain't broke.
