Been in our new house with pool for 3 months now. I have just switched to the BBB method because the previous owner lived exclusively by the "5-pucks of stabilised chlorine and shock the pool once a week (with stabilised stuff) in the summer" method. My CYA levels are >100ppm. In fact, they are probably >200ppm because I diluted the pool water 50:50 with tap water and it still read at over 100ppm... YIKES. Yes, I'm probably supposed to drain the pool to drop the levels, but I'm hoping that backwashing the filter will gradually reduce the CYA.
So my first question is: will backwashing really work and how many times will we have to backwash to reduce the CYA? The pool is nice and clean and we've only had to backwash the filter once so far!
Secondly, if I have to drain the pool, can I use it to water the lawn? I don't want to just pour the water into the street. (Water is expensive and I feel guilty just throwing it away when it's so scarce here in California!).
Thirdly, I know that excess CYA is 'bad' but seriously, how bad is it really?? The pool is clean and sparkly (with the exception of a few yellow algae spots on the warmest parts of the pool wall that I scrub off) so it can't be affecting the FC too much, can it?
Which leads me to my fourth chemistry geek question:
When you measure FC and CC with the Taylor K6000 kit, is the part of the total chlorine that is 'locked up' by the CYA measured by the kit? Does it fall under the FC or CC measurements? I just want to be sure that when I measure the chlorine and add bleach that I'm putting sufficient in there!
I just got the Taylor kit (I was previously using Walmart's HTH 6-way kit) and here are my readings:
- FC 0.6ppm (too low, I know, I added my bleach and will re-measure later!)
- CC 0.2ppm
- Alkalinity 220 ppm (the fill water is 190!)
- Hardness ~1050ppm (fill water is 270ppm). Was hard to measure in the pool water because I had lots of pink floaters and got - the 'wandering endpoint' despite adding 5 drops titrant to the water before doing the test...
- pH 8.0 (it used to hover between 7.5-7.8 when I was using the pucks but it's been steadily increasing since I switched to bleach. Fill water is pH 7.2-7.5. (I have to add 1.5 inches of water a week at the moment due to evaporation.). Just added 1lb dry acid and I'll re-measure tonight and assess the pH change. I'm aiming for pH7.5.
- CYA >100ppm. Is there anything that can affect this test (i.e. high hardness?!) and give a false high reading? Just hoping!
I'm still in the experimental stage of adding the right quantity of bleach frequently enough. Pool holds approx 10,000 gallons water. And I've been adding 50 fl oz 10% bleach about twice a week. Would I be better off adding less but more often? What is a typical schedule for adding bleach to an outside pool in the blazing Californian summer when your CYA is really really high?! I'm aiming to add enough to kick it up to 5ppm (because of the periodic spots of algae and knowing that it will drop quickly in the presence of ever-persisting sunshine). Is this about right?
Last question: how long should you typically wait to swim once you've added a jug of bleach (with the pump running) and how long after adding acid? We usually have the pump running for 4 hours in the morning since we swim in the late afternoon, so I add my chemicals early in the day (I assume that my high CYA will protect the Cl from the sun!)
Thanks for any input!