Tom, WP always had water circulating while water was heating. KA was still Hobart when the 19 series came out, as we all know. I think after WP acquired KA, they didn't want to upset the apple cart too much, along with the limits of our electrical system and 120v power, ad continued the static water heating design until the 23 series. I always thought that wa so stupid of KA to not have water circulating while water was also heating. One of the reasons why I wouldn't buy a KA.