Hi folks, I joined this great site several years ago and have often followed the various topics and always tried to follow your TFP methods. As a consequence I don't normally have any problems, it's a very rare occasion when I've had to slam the pool. I've always slammed to breakpoint as soon as I've noticed the chloromines getting over 0.4ppm but usually upping the dose to bring FC to around 7ppm once a week stops chloromines rising above 2ppm gets me back to zero, and up to now it's been a relatively short term painless exercise but it means I don't have any experience in longer term 'proper' slamming lasting for several days.
My current numbers are: CYA 20, FC 2.5, TC 2.9, PH 7.6, TA 108, CH 165.
CYA dropped low due to winter rainfall pump aways... normally I try to keep it around 32ppm. Prolonged periods of very hot sunny days in the UK aren't normally a problem and so far the low CYA hasn't been either. That IS gonna change but maybe ideal whilst I slam?
I test daily with DPD liquid regants and manually dose Liquid Chlorine to target FC at 4ppm. The FC demand seems to always be between 1.4-1.7ppm per 24 hrs giving a FC low point of 2.4- 2.7ppm no matter the weather. Although I've rarely had any problems, I'm wondering if I may have been sailing to close to wind and getting away with it and if I need to tweak those FC levels up slightly because I now have sure signs of algae!
I first noticed what appeared to be thin lines of dirt continually appearing roughly in line with the returns and small thin traces on the sloping walls of the deep end. I tried a sock in the skimmer when vacuuming (several times... but the 'dirt' kept reappearing within an hour of circulation starting up. At that time the chloromines were still close to zero. Then the water went slightly cloudy... chloromines leapt up to over 0.4ppm. Unfortunately we were then away for four days and although I upped the FC to 15ppm and also stuck a couple of large stabilised tablets in the skimmer basket... when we got back I noticed light green patches on the floor around the slope and deep end which came up into a nice green dust when swept! The FC was down to 5.5ppm - chloramines 0.4ppm... and realised I had a REAL problem starting up!
The questions I'm hoping you guys can answer for me are... what is the breakpoint for CYA at 20ppm?... I want (if possible!!!) to keep using the pool and realise slamming is gonna take several days as its now probably on the verge of getting worse!!! .. but would prefer not to keep TOO far past whatever it is so we can still swim!
Also... I can't run the pump 24 hrs due to neighbours beliving they hear a slight annoying hum when in bed!! The pump is in an enclosed brick building 10yrds away from their house with a high wood fence and high mature trees between... I don't see how... it's not especially noisy even close up... but there you go!
I intend to run 5.30 am - 11pm whilst slamming with a last check and dose if required around 8pm. So second question... can I get away with not circulating overnight?
I use liquid chlorine that is labeled as 14-15% sodium hypochlorite... but there is no other info or label on the container. It's what my local pool installers store supply... but other than using what I need to get FC to 4ppm I don't know much about it. I decant that into a 5gall strong plastic camping style water container with a tap on one corner and stick that on a shelf so I can fill into a small measuring jug. I dunno how to work out the volumes for a sloping wall vinyl pool but 20 fluid oz gets me from around 2.5 to 4ppm ok.
Wish we could get your recommended test kits over here but unfortunately it's not possible unless you guys go into the export business!
Sorry for the ramble... would love to get your thoughts, and grateful thanks for a brilliant & informative site.