Where on Eastside?
Best pool on that side of town is likely to be Bellevue Aquatic Center. 25y 6 lanes. It isn’t crowded. I mean at all. Often you can get a lane to yourself. And is kept clean. Pay no attention to the schedule though. It’s pretty much a free for all, except when masters or a school swim team or some other group (aquarobics) have the entire pool to themselves. Pool is run by the city so no membership. Water temp are mid to high 70s. It’s perfect.
Mercer Island and Juanita HS are old rundown pools. Water quality may be adequate (I don’t know) but the facilities are run down.
There’s a brand new pool at Columbia Athletic Club in Kirkland. Open only to gym members. Their older small pool was a cesspool of child bodily fluids though. Not sure if they keep the new pool only for lap swimming or allow dirty diapers into that one too.
There’s Gold’s Gym in Redmond with a 25y pool, where most eastside triathletes seem to train. I’ve not been there. There’s also Redmond city pool and there’s a pool in Issaquah. Also not been.
Pro Sports club on 148th by Microsoft has three pools of varying water temperature. Expensive membership.
Bellevue Club, as posted already, has a 50m pool only for members. It’s a country club or golf club or something. Thousands of dollars to join.
Best pool in the greater Seattle area, and my favorite, with a really great water quality, is King County Aquatic Center. Way down in Federal Way 30 miles south. No dirty diapers. It’s a 50m 8 lane Olympic pool with a dive tank and seating for thousands. The real deal. And they let us swim in it. But the drive. Getting there at 5:30 AM takes 30 minutes. Returning at 7:30 AM in rush hour traffic takes over an hour. :-/