What is it, what does it do and how do I use it?’ Part 1 of 7: Bottom drain

Most older pools have one but new pools have to have either 2 or none (VGB2008). These allow us to do a few things! We can draw water from the bottom of the pool during regular operation which keeps the water temperature more even (thermocline effect), allow us to lower water below the skimmer level if plumbed properly and help keep water feed to the pump if the skimmer basket gets full. Some pools have the bottom drain plumbed directly to the skimmer, which can cause a suction entrapment issue if the skimmer basket gets full but these days, they are plumbed directly to the equipment pad with a valve to control how much water is drawn from there. The industry recommendation is 25% of the total flow since there is not much contamination down there.