Can't raise Alkalinity

Problems relating to pH and total alkalinity.
Increase ph, increase TA. Reduce pH, reduce TA.
pH chemistry advice and techniques for the pool.
blidome
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Re: Can't raise Alkalinity

Postby blidome » Fri 28 Jun, 2019 06:43

Mystery solved!

I'm happy to report I have finally got to the bottom of the problem.
There were two issues causing it, the first being that the redesign of the plant and pipework over the winter to accommodate the UV unit has caused a syphon effect on the acid supply line so that even with the pump off acid is been sucked into the pool. The second issue was an idiot manager who has been topping up the day tanks and not recording it on the test sheets, so I believed no acid was being used! It was only because he went on holiday yesterday that I have managed to find this out.

Thanks all for your help and I will look into the Cya/disinfection thing some more.


Teapot
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Re: Can't raise Alkalinity

Postby Teapot » Fri 28 Jun, 2019 06:58

I haven't much time at the moment but:
Without CYA, as you can see from your graph you are struggling to maintain good disinfection. That said when you are dosing 1.5ppm you are subjecting people and their swimming costumes to nearly 8 times the amount of disinfection required.
Chlorine when added to pool water becomes hypochlorous acid, that is the actual disinfection chemical.
Because you are struggling to maintain chlorine your doser is working overtime against the sun's UV photo degradation. But you are adding chlorine and this becomes hypochlorous acid, an acid, added at a rate that is probably pulling your pH down. You are adding bicarb to try and balance this and losing.
If your chlorine was stabilised with either CYA or ACO from Dryden's, your chlorine dosing will drop rapidly and your pH probably stabilise nicely.

Why on earth are you fitting a UV system? UV is mainly used to break down chloramines in an indoor pool. You won't have chloramine issues because your level of chlorine means the pool water is in a permanent state of shock.
Also the sun and mild breeze will alleviate any issues. I can only surmise that a convincing salesman has done a number on you and the board. UV will do nothing to aid you.
Adding CYA to a level of 30ppm means you can chlorinate between 1.5ppm to 2.25ppm well within guidelines. You will however see a big reduction in your chlorine usage and more stable pH.
What are the water test results for your top up water, I am assuming you swap 30 litres of water per day per bather as per PWTAG's guidelines. What are your bather numbers?
Adopt the practices mentioned here and you'll be dancing the futterwacken in no time.
blidome
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Re: Can't raise Alkalinity

Postby blidome » Fri 28 Jun, 2019 08:40

Hi Teapot,

Turns out pipework alterations and other factors were making the acid syphon into the system from a full day tank and the pool manager was refilling it every morning without recording it so we didn't know!

I'm not solely in charge of the system, I volunteer in the plant room and am not one of the trustees. I wasn't involved in the off season decisions about the alterations or ordering of them. However, despite what you say, we do experience chloramine issues. Last season it even shut us down for a day and on several occasions we had to shock it overnight. We don't know exactly why but we do suffer with relatively high combined values, maybe wildlife, maybe groundwater or seawater, maybe something else entirely we don't know about, but it is another reason we decided to keep levels fairly high this year and I imagine why the UV system was looked at by the trustees.

Problem is the pool in its current form is around 50 years old, has had numerous alterations over that time and was neglected by the council for many years before being taken over by a community led charity just last year so please forgive us if we're still learning the ropes.

I will try and find some bather numbers for you but, being an unheated open air pool and with the weather so far this season, they have not been big, unlike last year's heatwave which started the day we opened and which meant running at capacity every day with long queues outside until it was over. I can't remember the top up water test results offhand but I'll come back to you shortly.
Denniswiseman
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Re: Can't raise Alkalinity

Postby Denniswiseman » Fri 28 Jun, 2019 09:44

At least you have found out that your problem was with the acid syphoning
The only other thing that should be implemented is proper documentation of the chemicals used so everyone is aware of the usage and can react to excessive consumption

Good luck
blidome
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Re: Can't raise Alkalinity

Postby blidome » Fri 28 Jun, 2019 11:01

Hi Dennis,
Exactly, I have told him before that it all needs to be recorded but I think he's deliberately ignoring it. I think he assumes that if he knows that's good enough and we mere volunteers don't need to. At least it's on his shoulders if anything should go wrong but we don't want there to be a problem in the first place. I will whisper in the trustees ears as well as talking to him when I see him next. He needs to get rid of the chip on his shoulder.

Teapot, I have posted below the same time period as before but without the exaggeration of full scale. It looks far less scary.
Attachments
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blidome
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Re: Can't raise Alkalinity

Postby blidome » Fri 28 Jun, 2019 11:08

Teapot, the top up water tests as follows:
pH 7.47
tA off the scale (over 200. I did try the tablet method but I assume ours have gone off as I still had no reaction at 30 tabs i.e. 1180ppm which I do not believe for one second but I ran out of time to repeat it)
CAH 270
Free 0.03
Total 0.05 (not combined as I said first :oops: )
Denniswiseman
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Location: United Kingdom

Re: Can't raise Alkalinity

Postby Denniswiseman » Fri 28 Jun, 2019 13:09

blidome wrote:Hi Dennis,
Exactly, I have told him before that it all needs to be recorded but I think he's deliberately ignoring it. I think he assumes that if he knows that's good enough and we mere volunteers don't need to. At least it's on his shoulders if anything should go wrong but we don't want there to be a problem in the first place. I will whisper in the trustees ears as well as talking to him when I see him next. He needs to get rid of the chip on his shoulder.

Teapot, I have posted below the same time period as before but without the exaggeration of full scale. It looks far less scary.

Just think how easy it would have been if he had mentioned that he was puting in an excessive amount of HCL. You would have known what the problem was immediately.
The thing is he doesn't know anything as he wouldn't keep adding HCL
blidome
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Re: Can't raise Alkalinity

Postby blidome » Fri 28 Jun, 2019 17:50

I had written on the day sheet that the acid pump was to be left off until further notice and yet he topped the tank up twice without even thinking about it apparently. I wonder where he thought it was going!

Next issue will be working out how we can stop the syphon effect!

Thanks again :thumbup:
Denniswiseman
Pool Industry Leader
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Posts: 1200
Joined: Tue 06 Sep, 2011 05:48
My Pool: 10k inground fibreglass, Telescopic Cover, Hayward Powerline pump, Quality filter with glass media, 27kw output heat pump, K-2006C test kit
Location: United Kingdom

Re: Can't raise Alkalinity

Postby Denniswiseman » Sat 29 Jun, 2019 02:55

blidome wrote:I had written on the day sheet that the acid pump was to be left off until further notice and yet he topped the tank up twice without even thinking about it apparently. I wonder where he thought it was going!

Next issue will be working out how we can stop the syphon effect!

Thanks again :thumbup:

Exactly the blokes an idiot and shouldn't be in charge
The syphoning should be up to the installers of the UV system who altered the pipework
blidome
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Re: Can't raise Alkalinity

Postby blidome » Sun 30 Jun, 2019 15:18

They won't be coming back. They didn't do a great job of the pipework, it had many leaks and is badly laid out and poorly assembled so the trustees held a fairly significant portion of the payment back until it was fixed. They just said 'keep the money then' and walked. They weren't just the cheapest quote either apparently. It's a new contractor who will be completing the UV installation from the pipework they left for it. Been thinking and, once that is installed, I believe we'll be able to easily re-site the injector so it won't syphon. For the moment as long as we don't fill more than two-thirds full it doesn't syphon anyway.

I think I'm slowly getting through to the manager a bit about records after talking to him but there are issues with his priorities, which I won't go into here, that are upsetting some of the trustees too so I'm not sure how long he'll survive anyway!
Denniswiseman
Pool Industry Leader
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My Pool: 10k inground fibreglass, Telescopic Cover, Hayward Powerline pump, Quality filter with glass media, 27kw output heat pump, K-2006C test kit
Location: United Kingdom

Re: Can't raise Alkalinity

Postby Denniswiseman » Sun 30 Jun, 2019 16:58

You can't have the tail wagging the dog
Teapot
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Re: Can't raise Alkalinity

Postby Teapot » Fri 05 Jul, 2019 15:42

blidome wrote:I had written on the day sheet that the acid pump was to be left off until further notice and yet he topped the tank up twice without even thinking about it apparently. I wonder where he thought it was going!

Next issue will be working out how we can stop the syphon effect!

Thanks again :thumbup:

Glad to hear you found the source of the problem. What type of chemical injector is on the end, ducks bill type or non return valve?
blidome
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Re: Can't raise Alkalinity

Postby blidome » Wed 10 Jul, 2019 07:10

Hi Teapot,

I think it's still a ducks bill type. The Chlorine was changed to a new style one which has rubber tubing around a pipe with holes drilled in it, but I believe the acid stayed the same as last year.

Part of the whole issue is that we cannot run the pump as fast as we would like to due to cavitation problems, so the pressure in the pipe is less than it ought to be. When we can fix that it will probably cease to be a problem.
Teapot
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My Pool: 12 x 24 (45m3) liner pool, Triton TR60 filter with AFM glass media (Activate) and variable speed pump running 0.08HP
Location: UK

Re: Can't raise Alkalinity

Postby Teapot » Wed 10 Jul, 2019 08:30

The duckbill ones do degrade so a seasonal change is necessary. Not knowing the plumbing I can't comment. If you had issues with high chloramine levels people are most likely peeing in the pool and/not showering before swimming.

Regarding not being able to run the pump as fast as you would like, what is the flow rate and system pressure? Look at my pool equipment signature, although mine is domestic and therefore not as heavily used I run my pool at the best speed to give me 4 turnovers per 24 hours which removes around 99% of contaminants and the system pressure is just over 1/2 of 1 PSI. This still produces water so clean and clear 0.5 NTU at best 1 NTU worst case. 0.5 PSI still exerts sufficient pressure to pack the glass media tight enough to capture everything but the finest dust and using flocculant it will capture that. Public health England recommend the use of flocculant.

This saves a lot of energy as I run around 60 watts on filtration. However when designing this setup I did not expect results as good and these are echoed by my customers who have me engineer their pools. I was told cavitation would happen, apart from short bursts just like any other pool I do not suffer cavitation. I was told the filter cannot work at such low pressure yet it does and has been for 7 years, likewise for customers who experience the same.
So much of what is documented by PWTAG and others are just old ideas that have been proven wrong.
I follow green technology and noted in a submission in a Norwegian journal they have designed a large commercial pool along the same lines as I have and everything is working.

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