Hi,
I've been a frequent visitor to this forum for probably 8 years. Thanks for all of the good advice!

I now inherited a pool maintenance problem; 17,000 gallon plaster pool that is green. Sand filter.

The previous pool maintenance was to add tri-chlor tabs.

I had the water tested with the following results:
CYA 100+
pH 6.8
TA 20
FC 1

The testing lady at the pool supply store said that I should disregard the CYA, although the automatic print out said in large bold letters to DRAIN 1/3 OF POOL WATER AND RETEST!

She actually readjusted the CYA level to 90 and reran the test, which resulted in about $150 worth of chemicals recommended. I DID NOT PURCHASE ANYTHING BUT 4 GALLONS OF LIQUID CHLORINE.

I have since raised the pH to 7.2 and the TA to 60 using Borax and baking soda. I have also removed about 1/3 of the water and refilled (before adjusting the pH etc).

I am going to retest and I will post the results this afternoon.