I have a 8x4 meter pool which holds about 50000 litres of water. I live in Mazarron Costa calida Spain, and for 5 years have had pool trouble.
I have replaced the sand twice, the last time 6 weeks ago. The test kit I use is tablet type and only gives cc and ph readings. No one in the area sells kits to enable me to get the cya level or the free chlorine level. There are no pool stores around that analyze the water either. I cannot buy the taylor kit on line as they do not mail it from the states to Spain.
My problem is that the pool has always shown 0 cc chlorine in the water. I read here about chlorine lock and have now used 5% bleach for several days (cant get 6% here) and nights to maintain total chlorine level of around 3ppm however overnight i was still getting massive loss where in the morning it can be back down to 0.3ppm PH is holding at constant 6.8. I can be using 4 or 5 chlorine tablets at a time and the reading is always 0, (except in the area of the floating chlorine dispenser)
When I shock the pool the reading goes up for a few hours but the next day is always 0 again. I tried the bucket test you described a couple of days ago after several days of bleach treatment, and was delighted when the overnight chlorine level held at around 3ppm. However last night when testing the pool in the morning it dropped from 3ppm to 0.3ppm
The water is probably around 7 years old and after the recent bleach treatment has looked fantastic and really sparkles however the chlorine problem continues as i am adding around 12 litres of 5% bleach every day to maintain any chlorine level.
Losing the will to live as we only use the pool for around 6 weeks in the summer and I must spend 20 hours a week cleaning and trying to maintain the bloody thing! Not to mention the fact that I am single handedly spending this country out of recession on bleach alone.
Any advice appreciated before I do the decent thing and end it all!