Is low TA a problem?

Jump to latest Follow Reply
A

andy33gmail

0
Jul 22, 2018
16
Cambridgeshire, England
So, this is my first post here, although I’ve been using this site as one of my primary sources of information for the year I’ve had my pool. Sorry for its excessive length!

My water supply has a very high TA, nearly 180, which I understand is because water is in Cambridgeshire is mostly sourced from bore-holes due to its flat landscape and fairly low rainfall

Until now, I’ve always had issues with a *high* TA. I nearly added a fountain that I could switch circulation to in order to aid out-gassing, before I realised that I could angle the jet upwards

However, I last measure the TA to be at 30. pH is very stable - I set it to 7.00 and it holds between about 6.94 and 7.04 almost 100% of the time. ORP very stable too at an alleged 750mV, only varying by a few points ... with a typical free of 0.5 and combined of nearly zero - you can see a slight colour change - I’d guesstimate 0.1. CYA at 0, no UV, silver or other chemicals in play

Given everything else is stable, do I need to worry? I’ve bought a few Kg of bicarb which I can tip in if needed.

I suspect a slightly higher pH would reduce acid demand and therefore reduce the rate I lose TA? There’s not much objective reason for keeping it at 7, other than the water feels “nicer” on my skin and in theory it should allow the same disinfection with slightly less chlorine

I know that with plaster pools, low calcium hardness (which I think is one of the three things that add up to total your TA?) can case dissolving, but is there any issue for me?
 
Welcome to the forum! :handshake:

A low TA (under 50) is a danger of crashing your TA and pH. And a pH of 7 is just low enough that it might eventually mess with your liner and a heater if you have one.

I would suggest getting your pH to 7.4 or so and let the TA balance on that. As your fill water is high in TA, any splashout etc will require adding some water and your TA will creep up.
 
Thanks for your help :)

Pool is heated to 30c off my central heating with a titanium heat exchanger

There’s also an electric heater that isn’t used (came with the pool, so put it in as a backup)

By TA crashing, you’re meaning that one day I’ll find it has TA of about 0 and pH well below 0? I realise the pH can nosedive if there’s NO alkalinity - but is there a possibility of the TA (which has gone from 80 to 30 in about 4 months) suddenly going - like how a pool’s chlorine demand can run away

I realise that typical guidelines give a minimum of 7.2 or 7.4. I guess the problem with having it at exactly 7 is that the water will sometimes be slightly acidic, hence your concern about eventual equipment damage. I guess for that reason alone, it ought to be high enough that it never dips below, so 7.05+?

But anyway, am I right to expect that from here, increasing the pH will stop TA falling further, and for it only to increase on next water change
 
The TA may not drop to 0 but the pH can get unstable and drop well below the range it can be tested with normal test equipment.

If you let pH to rise your TA should not drop further. Hopefully come up to 50 ppm or so.
 
Okay, I’ll set it to 7.4 and see what happens :)

Any point in adding bicarb or doing a partial water change (13% I think?) to get it to 50 for now, or just measure it for now?

There’s an audible alarm if the pH goes out of range, so if it does become dangerous, at worst I’ll know as soon as I’m back from work so it won’t spend too long corroding!
 
If things are stable I see no reason to intervene with chemicals. Depending on how much fill water you have to add over time I would suspect the TA will increase in due time.
 
Never. No need, there’s no UV.

It’s indoor, there’s a very modest amount of glazing, which doesn’t receive direct sunlight due to vegetation, and has privacy film on anyway to ... cut down on laundry. The UK’s having an especially good (as intense) summer right now, and even at that, I’ve only swum without artifical light twice.
 
andy33gmail said:
Never. No need, there’s no UV.

It’s indoor, there’s a very modest amount of glazing, which doesn’t receive direct sunlight due to vegetation, and has privacy film on anyway to ... cut down on laundry. The UK’s having an especially good (as intense) summer right now, and even at that, I’ve only swum without artifical light twice.
Click to expand...

If you add up to 20 ppm CYA to your water it will be much less harsh to skin, swimsuits, etc.
 

Enjoying this content?

Support TFP with a donation.

Give Support
Surely better (healthier) just to maintain a lower amount of sanitiser than to add significantly more and reduce its effect?

- - - Updated - - -

Currently below 0.5 (the lowest level on the Taylor), crystal clear and with no slime. I’d guesstimate 0.4

That said, when I’ve previously shocked it, people have asked me if I bleached my hair :-S
 
I use 30ppm of CYA in our hot tub and it is covered 100% of the time when not in use. I can tell when the CYA gets low and needs to be checked because the harshness of the chlorine is noticeable. Also, the swimsuits I wear in my hot tub wear out and fade much faster than the ones I wear in the pool with 80 ppm of CYA. I'll probably start using 50 ppm of CYA in my tub next time and see how it goes.

A pool will use about 5ppm of CYA per month. A hot tub will use 10ppm per month or more, I've found.
 
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply