First, I want to say thanks for the wealth of knowledge available here. This post may get long, but in an effort to provide the full picture, here is what I have:
We recently purchased the home we have been renting over the last year that has a 9 year old 9500gal IG exposed aggregate pool with attached spill over spa, treated with liquid chlorine and uses cartridge filter. The previous owners contracted with a local service to maintain it weekly while we rented and the pool has always been clear, but I have decided to take this over since purchasing.
I recently came across the BBB method just doing some general pool research and was hooked on the simplicity of it. I purchased a TF100 kit and have been monitoring the pool over the last couple weeks while the pool service continued to maintain it before we purchased. Most readings have been ok, but the pool service has been slamming the pool very hard each week, with FC readings of 20+ the day after service. FC does come down as expected over time, but usually only gets to ideal ranges by the time they return and do it all over again.
FC=16-20+ after service
The biggest issue has been growing reddish brown stains across the bottom and sides of the pool which I suspected was iron precipitating down from the ridiculous amount of liquid chlorine they've been using.
First goal was to get what I could in normal ranges
My current maintenance levels:
I added in boric acid purchased from dudadiesel($30 for 25lbs) to get borates up to 50ppm only because it was cheap and seems like it has a lot of benefits and would help prevent algae during the stain treatment.
With the info here, I then dropped FC to 0.5, ph to 7.1. I did an Vit C test and after verifying stain removal success. Yesterday I added in the recommended dose of polyquat 60. I then spread in 1 lb of AA powder also sourced from dudadiesel. The stains were 75% gone within an hour. I followed that up with 1 quart of Bioguard's Pool Magnet Plus (HEDP) and dropped in a CuLator 4.0 pack into the skimmer and ran the filter overnight. As of this morning the stains are completely gone and it looks like a brand new pool. Filter is still running.
At this point the only potential issue in the pool is the calcium hardness is fairly high at 750ppm. I brought a sample to a local store just to verify my results. They also measured my TDS at 3400. I see some scaling (not a lot) on a few of the tiles around the surface of the pool.
I suspect the pool can still be easily managed with elevated CH, but I'm strongly considering doing a partial drain and refill now to get the CH lower and also remove some of the now suspended metals my AA/HEDP treatment has lifted off the surface so I don't have to keep adding HEDP as frequently.
To avoid risk or damage to the pool pump I was just going to rent a 52gpm submersible pump with large hose from home depot for ~$40. The local family owned pool store who supplied with PQ60 and HEDP are actually pretty good and knowledgeable. They did recommend trying and getting the CH levels down with a refill. They also suggested to turn the pool pump off for a day or longer to let a lot of the solids settle to the bottom and then do the pump out, hopefully evacuating a higher percentage of the tds/metals/etc. The house is on the water and although it is raised quite a bit from added earth, I will only drain 1/3 or maybe a bit more at a time, to keep the pool safe and then refill. Probably do this 2 times, maybe 3.
My fill water is city sourced and has a base CH of ~125, so unfortunately it will probably take a good bit of water replacement to get the CH down.
Am I wasting my time/effort or does this seem reasonable to move forward with doing a partial drain/refill to reduce CH?
Does turning the pump off for a day to let solids settle to the bottom sound reasonable or is this risky/have no benefit?
And last but not least, it’s only been 24 hours since the stain treatment – the write ups here are usually recommending to wait 48 hours and bring FC and PH very slowly after. Should I wait longer to replace water or just have at it since the stains are gone.