The other day we had the pool drained and cleaned. Apparently, the pool is supposed to be drained once every several years or so and have new water put in. If not, there is an accumulation of Total Dissolved Solids that makes keeping the pool clean very difficult. I've lived here for over nine years and never had this done before. I have no idea how long it had been before that.
Once the water is out of the pool, the plaster is given an 'acid wash.' It involves pouring a cleansing agent on the sides and bottom of the pool and then scrubbing.
It took about 6 hours to drain the pool and twice that long to fill it back up. Now we've got a much cleaner looking pool and the water should be easier on the new pool equipment we installed earlier. 
