That is a Ductsox. They are out of Kentucky. It’s a fabric HVAC duct that has holes in it that wash the windows with air. There is a 3 ton dehumidifier in the mechanical room the supplies it. Then a vent in the wall that is the return. When the fan is in it pressurizes. When it’s not it deflates.
Thanks. We tried to think of everything. It is not treated. I use 3” chlorine discs so it drips into the skimmer and go through them before returning to the pool. There is no debris of any kind or wind so it’s almost maintenance free. I robot vacuum one or two times a year and toss chlorine in it on occasion. Maybe once a year I have to adjust it but not much. Pretty low upkeep.
I worry about your CYA with your use of the tablets/pucks. Over time the stabilizer (CYA) in the pucks will build up. The only way to lower CYA is to replace some of the water. The more CYA you have in the pool the more FC you need. Strips are not very accurate at all. You might want to think about getting a test kit that tests CYA. Walmart has one that has the CYA test in it.
I’ll check that out. I do add water occasionally but have never drained it. The liner and heater were new in 2017 so it was drained then. That’s the last time. Now that you mention it. I’m wondering if the water coming out of the condensate drain will be clear or with it still have chlorine/cya in it.
I use liquid chlorine. I get it from the ACE Hardware up the road. Some people get it from the pool store. They "loan" out yellow jugs (2.5 gals) to refill as needed. You can also get liquid chlorine from Lowes, Walmart, Home Depot BUT be very careful getting it from there as some don't rotate their stock or store it outside in the sun. Two things lower the % of work chlorine-time and sun.
I use the TF-100 test kit. It is the best bang for the buck as it has more of the regents we use most often. Test Kits Compared this will show you the different test kits we endorse. Look in my signature below for the red link to the TF-100 kit.
With your pool being inside your chlorine needs will not be that high. Now if you have a large swimmer load that will change things a bit due to what humans bring to a pool.