I've been working on resurrecting an in-ground pool.
A bit of history:
From some permitting records it was installed originally in 1979. It's a kidney shaped and I'm guessing 25k gallons.
We purchased the home+pool in 5/10 as a bank owned. The pool of course was opaque and difficult to judge its condition.
The first order of business was to start the remodel of the house. In concert we started to determine condition of the pool.
We immediately found out the pool was is VERY sad shape. The equipment (1.5 hp pump and undersized sand filter) appeared to be original equipment. We hot wired around the non-functional mechanical timer and were able to restart circulation.
The county mosquito abatement office also paid a visit to ask if they could add some "guppies" to our "pond". I had to sigh and tell them that the frogs living in it should be sufficient until I can get it cleaned out.
As it being completely opaque we started to "dredge" out the bottom. Trust me, "dredge" is an accurate term. We would spend about 2 days per week bringing up what seemed a "bottomless" amount of palm fronds/leafs and "goo" (it had gone septic from the smell). Of course every dredging operation would result in the water column going BLACK. Not "green" or "minty" or "cloudy", completely "BLACK".
By the fall of '10 we started adding some liquid clorine and flock to get some clarity to what was left in the deep end. It was at this point we found: An 8x12 outdoor carpet and a metal baby's high chair (we started getting scared about what _else_ might be hidden in this "pit"). After extraction of those, we managed to get a fairly clear water column, but as winter approached, we placed a "tarp" cover to wait it out till spring.
In the spring of '11 we replaced the ancient equipment with a pentair SVRS and a cartridge based filter. Used that to vacuum remaining debris (with almost hourly cleanings of cartridges). After many brushings and "shocks" we had a crystal clear pool! Of course, we had simply lit a time bomb due to relying upon "advice" from the LPS.
After a year of a "nice" pool in '11, we left it open during the winter. It was also evident that the gunite plastering was deteriating.
In the spring of '12 we had "green" water coluum and debris to remove. Got that cleaned via "shock" and vacuums. Everything was fine, of course .... until it wasn't.
We started having abnormal chlorine consumption to the point of it being "never enough". The LPS would tell us "everything is fine, just add more tabs/bags of chlorine, it's normal".
I left town for a week, and came back to a perfectly clear water coluum, with green algae covering every underwater surface.
On the early morning of 8/12/12, I vacuumed the algae that I could, brushed the rest, and threw in my last pound of cal-hypo "super shock".
FWIW, here's the numbers from the LPS on 8/12/12:
FC: 5 (I had added a pound of cal-hypo 12 hours earlier)
On 7/15/12 we had these numbers from the LPS:
FC: 5 (was also after adding some cal-hypo 6-8 hours earlier)
Sadly, I did buy more "stuff" at the LPS on 8/12/12: 6 lbs of cal-hypo "super-shock", a quart of "copper algicide", and 25 lbs of "tabs".
I finally decided to figure out this on my own and am happy I found this site. My Tf-100 is on order (I splurged and got the "stirrer" as well). My only test kit at the moment is the "Leslies OTO Deluxe" ...
In the meantime, I'm adding the "pounds of super-shock" I have in inventory each evening and my "Leslies OTO" kit is registering _some_ chlorine each morning. I'll return the algicide, and either return or hold the tabs for future.
Currently the water is a bit cloudy but clearing.