Pool alkalinity

Corona - not sure, but I think my scuba tester might be on the way out as it gives wild readings.

Looking on tinternet for replacements, I am quite taken by ColorQ. I think you have rated them in the past. Still good?

Now, on their demo, they convert TA to ‘Adjusted Alk’. In the video an initial Alk of 126 suddenly adjusted to 109! Interested to know what to follow!

Listening to you way back, I have sdopted the approach that CYA is all important and my first test, then TA that I run as low as possible - usually under 90. I only test for PH monthly, as I control the TA with HCl and aerate the water, pH has never benn avove 8ish. I test CC monthly and FC weekly. Maybe all a bit cachanded, but it works.

My question - what is AA in relation to TA, other that CYA is involved? I thought CYA is there only to control Chlorine? Is my TA reading of 90 on my tester in fact much less? I remember once you ssying that a TA of 40 odd would be good if everything else was correct.

The latest color Q’s are a redesign all new parts and I havent had one to test. So I cant give anymore guidance on that, one of my old customers bought one about a month ago and I havent heard from them.
Adjusted TA does sound like they have tweaked the reagent, possibly to remove the influence of CYA, I will ask the MD of LaMotte EU.

We know that Alkalinity is used as a buffer, albeit at a pH too high for pools usually. Any largish amount of a chemical can buffer a solution and that happens with CYA as well. Being an acid it forms a buffer solution pulling the pH down and Alk pulls it up, together you get a well buffered solution that is very pH stable. That is why I suggest a lower than industry level of Alk for liner and fibre glass pools as we and my colleagues have experimented around the world trying this out. Different water in different places but we get a pretty stable pH with Alk between 40 & 60ppm. That said if people are not having to add pH minus or seeing a pH drift upwards with salt chlorinators then we have things balanced nicely

The ColorQ in the demo is a Pro 7 that works with the tester sending the readings as they are taken to an app on a phone. I think it might be the app that calculates the adjusted figure, as the tester showed 126, but the app readings gave it as 109 ‘adjusted’.

i’d be interested what your colleagues think of it.

Busy packing for France but I will call and ask.


Hi @Corona , I use bromine in my spa, as that’s what the manufacturer recommends. As a consequence, there is no CYA added. I’ve increased the alkalinity in the water to the recommended 100ppm but I’m having issues balancing the pH. If there’s no CYA to pull the pH down then would you recommend reducing the alkalinity, or is there something else I can do ?
Have a good break in France and breath in the relaxing air :relieved::sunglasses:

Edit: I also use MPS every week to reactivate the bromine, but looking online, some people say it should be used very sparingly as it can have other effects.

I am not a fan of bromine, I get that its more stable at higher temperatures but its more toxic to humans as the brominated disinfection byproducts are also breathed in at the level we sit in spas etc.
There is absolutely no need for high or industry standard levels of alkalinity in plastic pools or spas. Whilst chlorine does breakdown quicker in warm water its lower cost, no need for MPS (cost saving) and marginally cleaner response as its more active for me makes the difference. Not knowing the size of your spa but an average one would probably need a teaspoon (5ml) of javel.

Thanks for the quick reply, I know you’re getting ready to go to France. The tub is 1000l. I’m only really using bromine because the spa manufacturer recommended it over chlorine. Not sure why. As I’ve got loads of bromine left, I’ll use it up. Also got about 1 Kg of MPS and it does seem to help keep the bromine levels stable so I’ll use that up as well. So, in keeping the alkalinity at what online are recommended levels, I may have created the problem with unstable pH. Although you say no need to use recommended levels of alkalinity, is there a level that you would recommend ? Earlier in the thread you mentioned 40ppm for a pool.

You havent created the problem, the pool industry has high alkalinity for concrete, plaster and tiled pools with good reason, even then they are a bit higher than usually needed as pH has a bigger effect on aggresive water than alkalinity (in the langlier saturation term). The issue is vinyl and glass fibre simply do not need high alkalinity which means we can enjoy stable pH and even more beneficial on salt chlorinated pools that usually suffer an upwards pH drift through the process of converting salt water into chlorine.
My pool is around 45-50 ish on alkalinity but my supply water is very high in alkalinity so I have to reduce this over a season. Easy for me as I designed my air assisted backwash with producution of air bubbles when not in backwash to raise the pH and then reduce the pH with hydrochloric acid which leaves the alkalinity low but pH where we need it.
Your spa jets would achieve the same thing but what is the alk level of your tap water?
Yes packing but unlike usual I have a bit more time for a change :blush:

Ah. I didn’t realise that the high alkalinity requirement was because of materials used in pools. Makes sense when you think about it. Our water alkalinity is pretty low at about 25ppm as is hardness, because we’re on granite here. I usually up the hardness as well.

Aha, geographically I know roughly where you are. Because I did my industry training and one of my customers must be located not far from you, I got myself in a bit of a state trying to locate a sack of bicarbonate of soda to increase their pools alkalinity to “industry standards” I was staying with them for the week to sort out some plumbing issues so I ran several tests. I reported the results back to colleagues around the world and asked the opinion of our very clever chemist. That was the epiphany! I took water samples back home and tested them on a rig I had built. From memory at Alk of 45ppm there is still 7 times more CO2 in the air above the water so the off gassing is almost non existant but at industry levels its the complete opposite so pH rises are usual and so people by lots of pH minus all year long, great for sales in pool shops but completely uneccessary.
So began the journey with others of debunking the pool industry.
Yes some hardness would be desirable as would a slighlty higher pH to prevent the water corroding metal parts.

Thanks for all your help. I now know what to do … or not do :grin: