First off, this may be the best user-submitted, advice-driven website on the internet, and I'm not being even slightly hyperbolic. I've spent a great deal of time reading through the Pool School articles and various threads lately, and the amount of information that has been refined and perfected and happily delivered is pretty amazing.
Moving on, I'm under a bit of a time constraint so I don't have the luxury of posting an introduction just yet, so I'll try to be concise with asking for help on this issue and allow this to temporarily serve as an intro. I very recently purchased a home with a broken pool pump motor and old (quite old!), undersized filter, so I had them both replaced on Thursday (see sig for current equipment details + pics). I like DIY projects but I had a professional do this as my home warranty will not cover the equipment unless a licensed professional installs it and, perhaps more importantly, I wouldn't have known how to do it anyway and I shy away from projects that involve rewiring of any sort (the prior pump was a single speed, 2 HP, 2500 watt piece of ancient, rebuilt junk).
The pool has reportedly (prior owner info isn't reliable in my situation) not been drained in 5+ years and my default water in Las Vegas has a high TDS content, so I decided to drain the pool earlier today (thank you to TFP for showing me how to do this!). Additionally, I did not want to send a veritable swamp through my brand new and rather pricey equipment. Currently, the pool sits empty, it's dark outside and I'm going to begin cleaning it tomorrow at 5 AM sharp to make sure it's refilled ASAP.
My question is, do you recommend a certain chemical or combination of chemicals and methodology to remove organic stains from the wall and floor? I'm not 100% certain all of the stains are organic, but the majority certainly appear to be. I can provide drained pool pictures first thing tomorrow if that would be of help. I've read up on using a kind of bleach/shock/chlorine paste and elbow-grease as an alternative to doing an acid wash (I'm not entirely adverse to an acid wash but I would prefer not to do this). Also, do you recommend using a pressure washer to clean the pool and if so, is there a certain PSI cutoff point for a plaster pool?
Thank you kindly for the advice. Of note, I have purchased a lot of bleach and some CYA for my refill and I'm ordering the TF-100 tomorrow to make sure I get this right.
Pool immediately before drain with old filter in the background:
New VS Pump + 420 SqFt Filter (currently, pump is turned off + breaker is off as well):
Edit: I will update size of pool in gallons after my refill tomorrow, but my approximation of 20k should be close (pool is 8 feet deep in center and shallows out on the two ends + I know the GPH movement of the sump and timed this out accordingly).