Looks like we can put this thread to bed
FC dropped 0.5 overnight two nights ago and dropped the same last night. CC had been 0 for the last week, 0.5 crept in 2 nights ago but is between 0.2 and 0.3 (hard to tell with the 0.5 drop test but I think I only needed half a drop to get the faintest hint of pink back to clear).
Pressure has been holding at 16psi (starting point 15psi) for 48 hours so the topic of the thread has well and truly been solved.
I've found a couple of pool places that sell liquid chlorine but after doing the math, it's still cheaper to use my weak bleach (and for anyone in Spain needing to know, a 5L bottle or regular bleach with 37g of sodium hypochlorite raises my 15,500 US gallon pool by 2.75ppm). A 25kg bottle of Liquid chlorine with 127g per kilo for €24 equates to 17 bottles of bleach for €20. If you don't do regular school runs past the local store, you might want to opt for the 25kg LC and hang the €4 expense.
On this journey I discovered I had misread the pool filter. It said 100kg of sand so that meant 80KG of glass media (as per bag instructions) but beneath the 100kg on the filter it said 50kg of gravel and an email to Certikin confirmed the capacity to be 150kg (or 12Okg of glass media) so two more bags have been added.
I found an Ebay seller in the UK (filterbagman2) that adapted his 1 micron filter bags so I could attach them to 3 ½ inch plumbing parts I've fitted to the returns. 4 bags for £15 including postage (to the UK), cheap as chips! (good old English saying there). After the initial white dust coming through them they have settled down and are catching the tiny particles the sand filter doesn't. I guess now that they have a thin film of dirt that doesn't want to wash out they are filtering a bit better. I've had to take one of the bags off as two creates too much back pressure (PSI went up to 20 from 16) and a Jacuzzi effect was happening around the returns. I figured the tiny particles will eventually find their way to the single bag after a few rounds so I'm happy with that for now. The pressure of the water coming out of the returns is much greater than it used to be. You can now see the ripples half way down the pool (you could hardly tell the pump was on at all before).
One of the lights had blown some years ago and in pulling them out to clean behind, I had the opportunity to change it for a multi-coloured LED. Whilst testing the light remote on the new LED, the other one blew so now I have two LED lights which look amazing at night as they scroll through their colour range (€76 each from Leroy Merlin).
The LaMotte test kit is expensive but has proved invaluable in getting the pool crystal clear. I had issues with some broken parts by the service from Tim has been excellent, he has even said he would throw in a couple of reagents I was offering to buy (fingers crossed they are in the post). I couldn’t find the test kit on the Sword Scientific website (
Welcome to Sword Scientific) so he sent me to LaMotte.com (
FAS-DPD Commercial 7 Kit - 7022-01 - - LaMotte) and I’ve just spotted that his emails address changed from
[email protected] to
[email protected]).
The hardest part for me was water blasting between the tiles to remove the build-up of dirt/algae which had happened over the last 10 years. The lack of a proper pool cleaner contributing to that I guess (one for the shopping list, along with looking into SWG and Ozone and Other?).
So there we have it, the FC dropped from 16 yesterday morning to 11.5 this morning which is high for a pool without any use but the PH is still holding at 7.8 which could be causing the increased loss of FC. Once the FC is down to 6/7 (with my CYA at 55) I’ll monitor it to see what the loss rate is then. I've read in many places that 7.4 is the ideal number but I read somewhere on here that 7.8 is the preferred level but now that I look for it again, I can’t find it. I've also just read that a CYA level of 60/70 could also help with slowing down FC loss with sunny pools. I guess it will just have to be a case of trial and error.
I can’t do the BBB method as Borax is not available in Spain in large quantities (only in 6g packets so enough to do a 15k gallon pool would be a few thousand Euros) but I need to find a way of keeping FC in the pool so if there is something that could be substituted for the borax, that would be good to know.
Right, enough waffling, I’ll hang around with further additional tiny updates on getting it finely balanced and try to help others where I can with my limited knowledge. This site and it's polite and professional contributors has been a massive help but my suggestion of a Non-American section would have made life a little easier, one for the suggestion box.
Cheers Guys!