Hi Phil, just remember please its the air assist on the backwash doing most of the work, without that system you need a considerable backwash water volume to actually lift the filtration media to allow all the dirt to be shaken free. That waste of good treated water that made me persist in finding a better method and based on my friends help with what happens at commercial water treatment facilities. Sadly domestic filters do not normally backwash well and no one realises it until a cew years later, its why the industry tells people to change their sand around 5-7 years simply because down deep in the filter its dirty bacteria laden filth and creates problems for owners. Sadly the pool builders I have known have all moved on or retired which is why the big 3 in france have such a market share, (Desjoyeaux, Waterair and Magiline) No being mainly a summer resident no pool heating however I have 50 evacuated solar tubes waiting to come over if planning allow and I would probably add 2 small ASHP’s that would both be used when required but switching to just one in the closed season for underfloor heating in the house. Regarding pool type, the coque are fast install but you could be restricted in placement of skimmers and returns but not always. Liners are good because when the liner eventually wears out you can replace it with the latest trend in finish giving it a fresh modern look.
Hi Corona,
Thanks for your further comments. It’s really useful, as I am now able to close in on what we should go for.
Armed with my refined specification, I’ll now make efforts to find an good independent pool builder in our area who is happy to provide a pool that meets those requirements.
It sounds like the only aspect that might prove to be a bit of a ‘stretch’ is the air-assist backflow, given how ‘off piste’ you had to go to develop it, and how the main installers don’t provide it, so the independent guys may not be aware of this technology either. We’ll see.
Many thanks again.
Phil
No problem, I can assist if needed. Back to your use of UV?
Sorry, do you mean if I can’t find someone who knows how to provide air-assist you can advise what kit this involves, but if I can’t obtain air-assist, then UV is the fall-back option?
Yes, as the concept was refuted early on I set out to prove them wrong. I discussed my method with an Italian pool designer who is trying to produce chlorine free pools but in reality they have swapped one chemical for another but they have implemented my idea successfuly and a British guy who uses natural swim pond tech and air assist to aid backwashing but his system utilises bacteria in the filter to break down other contaminents, good system but £25k. Thus you wont find much on air assist.
Regarding UV on an outdoor pool its not really needed, the suns UV is far stronger at breaking down chlorine byproducts hence why its more used on indoor pools. What will be your primary sanitiser?
Couldn’t get the pump motor spinning this morning. Just a loud humming. Trued it a couple of times then let it rest while I cleared up leaf debris around skimmers (all in one end of pool). Fortunately it started up when I tried it again. My first thought was a blockage but I assume all large objects are filtered unless they are blocking things up the inlet side of filters. I’ve been correcting a very low TAC the last week. I had the water checked in Cash Piscines. Have now added 6kg of additive. Last count was around 60 if strip is to be believed. The last kg added yesterday and I need to check when pump has run a bit longer. Prior to that I was trying to increase the ph. It was around 6.8 or lower. Adding ph+ was doing nothing. Chemical was from 2022 and stored in a hot garage. Bought some new to add when TAC is good.
Pump just humming is most likely the start run capacitor, an easy two wire change its usually inside the pump wiring cover. Cheap part around €10 . discharge the old one before starting work with electrics off of course.
TAC for a plastic or liner pool is fine around the 45-50ppm the publicised 80-120 ppm is for tiled/plaster pools to preserve the grout etc. Excessive alkalinity leads to quicker pH rises. My alkalinity is 50ppm and been like that for years, havent added pH- for so long I cannot remember now at least 7 years. Alkalinity up is just bicarbonate of soda.
pH 6.8, please remind me how you are testing?
Wow! I’d love to have a constant 60 TA! Lowest I can get is 75-80 that I can maintain with a litre of acid every ten days or so.
I too have never added any Ph+ or -, in fact I cannot remember the last time I even tested for Ph! I let the pool users do that but so far no complaints or red eyes, so must be ok 
Hope TAC hasn’t gone too high after adding another kg yesterday. This is trusting Chat GPT!
We tested the ph with a Marina Chlor/Brome/ph tester by Marina - in fact with three different kits. Cash Piscines man tested with a strip.
I bought some strip testers there. I like using them more than the Marina kit but is it worth getting an electronic tester. If levels only need to be rough is a strip test adequate?
Actually we saw no indication of ph so not reaching the minimum measured level - or so it seems
I always found phenol red (drops or tablets) gave a far more accurate result than strips (and those cheap shitty chinese electronic pH testers)
I so hate that, same in Zyke my way.
As Mark said a low cost phenol red and DPD1 tester together with a CYA dot tester would surfice for most. TAC titration tests are usually low cost as well.
I will look at those testers. Meanwhile I’ve just tested the TAC with a strip and it looks like 80. I realise now I shouldn’t have added the last 1kg.
Ph is still not readable. I see that I need to be careful now adding ph+. Maybe 500g to kick off?
I am at the same point, but still going as i started at 200+ I wait for my pH to get to 8 and then add 0.5 litre of hydrochloric acid. It certainly has slowed down the pH creep that i used to see every season - i have a salt pool and the resulting lower TA has definitely kept the electrolyseur cell nice and clean as well.
Really happy you pointed me toward the capacitor. I tested it and it’s lost half it’s capacitance. Have ordered one.
Just remember not to touch the capacitor terminals when removing the old capacitor as it might retain some charge.
Good advice but I’m used to playing with valve amplifiers. Already tested and was sure to short the cap before connecting my ESR/Capacitance tester. It wouldn’t like several volts up it!
Best to short them to earth as described earlier but always worth a reminder 
Are there any down sides to that low a TA for a vinyl/fibreglass pool ?
Good question Peter, the only issue is if you use multi action chlorine tabs the pH can fall easier as they seem to be formulated for the 80-120ppm so the tablets are acidic, due mostly to their CYA content. CYA can also act as buffer in water so if the level of CYA gets too high the water can often sit a bit low in pH which I wonder if that is @MichaelL 's issue?
The only other effect is under the langlier saturation index the water could become a little agressive to metals anywhere in the pool setup, to counter this running the pH a couple of decimal points higher stops that issue. pH has a much larger effect on that than adding lots of bicarbonate of soda (alkalinity up).
Other than the above nothing else I have come across but a fantastically stable pH. This also removes the need for acid dosing which I have seen and also people reported going spectacularly wrong and 20 litres of acid entering the pool, just like that chap Mike on another french forum. Depending on your locations water you may not need to go as low as 50ppm, 60ppm may be fine but there is certainly no need to go higher only to have to counter a pH rising steadily.
