pH rising and unstable

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T

Tiken

0
Aug 13, 2017
14
Singapore
Hi all,

I have a lap pool and cannot get pH to remain stable.
Key parameters:

Pool volume: about 24,000 gallons, long and narrow, lap pool (10:1 aspect ratio)
TA: 80
CH: 200
TDS: 1100
Temperature: between 83 and 87 Fahrenheit
pH: tends towards 8.2

I use sodium bicarbonate to raise TA, and sodium bisulphate to lower pH.
I do not use chlorine in the pool, and no cyanuric acid.
Sanitation is through silver and copper ionisation (copper at about 0.3ppm).

Leaf load is light. Roof runoff is heavy when it rains.
Annual rainfall is high.

I am going through about 20 pounds of sodium bicarbonate and 20 pounds of sodium bisulphate each month and barely able to keep pH at about 7.6 to 7.8.
To reach ideal of 7.4 I would have to use even more chemicals. pH rises 0.1 to 0.2 each day after raising TA (overnight) and adding acid (next morning).

Is this a normal amount of chemical to use?
Any other possible reason for unstable and rising pH?
Any suggestion on how to treat better?

Many thanks!

David
 
Btw, how are you doing your testing? You mention TDS which is not a recommended test and usually indicative of Pool $tore testing. If that's the case, you really can't know how accurate those results are, so your TA could be sky high, quickly raising your pH, or your pH results could just be flat or wrong. It's highly recommended you do your own testing with a recommended kit so you can know the results are accurate.
 
Yes, sodium bisulfate will build up sulfates in the pool which will damage concrete and metal surfaces. If you have access to muriatic acid, aka hydrochloric acid, it would be better and cheaper to use that.
 
Thank you everyone for the replies. I was travelling and then sick and wasn't checking for replies, and had not set notifications through email. Have done that now.

A few quick responses. I live in Singapore, and we do not have access to liquid acids. I use sodium bisulphate which is solid granular form.
I measure TDS using a device that I think is mostly used by aquarium keepers. It's a simple meter made by Xiaomi.
pH is measured using a pen-type pH meter made in Taiwan that measures to two decimal places. It seems accurate.
I use a Pentair testkit to measure TA.

I've read about out-gassing and have tried adding acid and letting the TA fall.
The TA is now at about 30, and the pH is still rising at about 0.2 every 24 hours.

I used to use chlorine to sanitize the pool. Since 2 years ago, I switched to an Australian system ES3 (Enviroswim 3) that uses silver and copper ions for sanitation.
Since then I have not been able to achieve stable pH.

On the suggestion that I try pH at 7.7/7.8, I am concerned that the ES3 system may not work well at the pH. I am told by the manufacturer that, similar to chlorine, I need to maintain pH at about 7.2 - 7.4 for the system to be effective.

My pool water has not been changed since I built the pool about 16 years ago. But it rains a lot here, so I imagine the water has been renewed by rainwater through the years, and also topping up with tap water from time to time when the levels fall off because of hot weather or when I clean the filter.

I am wondering whether I should take the drastic step of emptying the pool and refilling. I don't know what else to do!

Thanks again for advice. Really appreciate it.

David
 
I have the same problem. I also have the Enviroswim ES3 and they have told me they have not heard of this before? I am still having the same problem with the sanitising system off for several months.

Refer below

Brisbane QLD Australia
Concrete 42000 Litre Pool (11000 Gallons)
Pebblecrete interior
Glass water/step tiles
Paramount PC2000 in floor cleaning
Pentair Tagelus TA60D filter with Glass media (1-3 micron M10 & M20)
Pentair easy touch automated
Pentair VS intelliFlo pump
Multi Cyclone 50
Enviroswim ES3 sanitiser (operates with in floor cleaner and skimmer i.e. on when the pump is on)
Commissioned end of September 2016
In floor cleaner run times 1.5 hours twice per day – total 3 hours
Skimmer run times 1.5 hours twice per day – total 3 hours
Total sanitisation – 6 hours per day.

I am having major issues controlling my pH. It creeps up from pH 7.2 to over 8 in under 4 days.

My concrete pool is now over a year old and requires 3 to 4 litres of acid per week to keep the pH around 7.2 – 7.4, preferred pH for Enviroswim sanitising system (copper/Silver, oxidiser and ultrasonic) and this is in winter or summer with no bathers.

Alk – 80 to 120
CH – 200 to 300
Copper – 0.1 to 0.3

When back washing I have noticed the water was light blue. After some research I believe this is caused by the high pH, making the copper release from suspension thus getting caught in the filter. There were also blue stains in the bottom of the pool, mainly around the in floor and down jets.

I have tried different situations i.e.
Different Alkalinity levels, 30 to 150, mainly 60 to 130 – problem remains
Enviroswim off for several months – problem remains
Pool pump off for 1 month – problem slightly slowed

I use a Taylors test kit for all my testings and have had several results compared to as many swim shops and I have found my results more reliable. Most shops were spot on to close but two shops have said some of my results were wrong but when they ran another test they got completely different results again….. they say there machine must be due for calibration. I have also had another pool company visit twice with their Taylors kit and we had the same results both times.

The guys from Enviroswim and the pool man that visited say there is something wrong with the interior of the pool but……. The peblers who came out to re acid wash the pool said NO WAY IS IT THE INTERIOR!

The pool builder has drained the pool and re acid washed the interior early October 2017 and now the problem seems to be worse?

I have been told that no one has ever seen or heard of this before, has anyone else had or heard of this issue?
 
I read somewhere on TFP that Sodium Bicarbonate helps to stop pH from falling, but doesn't work as well to stop pH from rising.
The recommendation was to use Borax to stop pH from rising.
I have ordered 18 boxes of 20 mule Borax, and hope to get it in a week or two, and also some test strips to measure the borax. My pool is about 93000 litres.
I hope that works.

Over the last 2 years, the pH has not stayed stable. Initially I did not measure the rate of pH rise, and to reduce acid use, I only lower pH when I wanted to swim, and at other times allowed the pH to rise. It leveled off at about 8.3 or 8.4.
The problem with that is that algae began to grow, not noticeable at first, as it was in the grouting between tiles and a thin film on tiles. Eventually I had to shock the pool with chlorine to get rid of the algae.

The other thing I've noticed is a blue crystalline crust forming on my ES3 ioniser plates. I think it is some copper salt. This happens when I add a lot of sodium bicarbonate all at once to raise the TA before I lower the pH. my TA goes down quite fast when I use acid, and also I think when it rains and dilutes the pool ... and it rains a lot here. Some of this crystalline stuff breaks off and returns to the pool, and it accumulates on the floor of the pool very visibly around the water return spouts, and this then needs to be vacuumed away.

Sorry I can't help much for now ... will keep posted on Borax use when I've tried it.

David


Avo1 said:
I have the same problem. I also have the Enviroswim ES3 and they have told me they have not heard of this before? I am still having the same problem with the sanitising system off for several months.

Refer below

Brisbane QLD Australia
Concrete 42000 Litre Pool (11000 Gallons)
Pebblecrete interior
Glass water/step tiles
Paramount PC2000 in floor cleaning
Pentair Tagelus TA60D filter with Glass media (1-3 micron M10 & M20)
Pentair easy touch automated
Pentair VS intelliFlo pump
Multi Cyclone 50
Enviroswim ES3 sanitiser (operates with in floor cleaner and skimmer i.e. on when the pump is on)
Commissioned end of September 2016
In floor cleaner run times 1.5 hours twice per day – total 3 hours
Skimmer run times 1.5 hours twice per day – total 3 hours
Total sanitisation – 6 hours per day.

I am having major issues controlling my pH. It creeps up from pH 7.2 to over 8 in under 4 days.

My concrete pool is now over a year old and requires 3 to 4 litres of acid per week to keep the pH around 7.2 – 7.4, preferred pH for Enviroswim sanitising system (copper/Silver, oxidiser and ultrasonic) and this is in winter or summer with no bathers.

Alk – 80 to 120
CH – 200 to 300
Copper – 0.1 to 0.3

When back washing I have noticed the water was light blue. After some research I believe this is caused by the high pH, making the copper release from suspension thus getting caught in the filter. There were also blue stains in the bottom of the pool, mainly around the in floor and down jets.

I have tried different situations i.e.
Different Alkalinity levels, 30 to 150, mainly 60 to 130 – problem remains
Enviroswim off for several months – problem remains
Pool pump off for 1 month – problem slightly slowed

I use a Taylors test kit for all my testings and have had several results compared to as many swim shops and I have found my results more reliable. Most shops were spot on to close but two shops have said some of my results were wrong but when they ran another test they got completely different results again….. they say there machine must be due for calibration. I have also had another pool company visit twice with their Taylors kit and we had the same results both times.

The guys from Enviroswim and the pool man that visited say there is something wrong with the interior of the pool but……. The peblers who came out to re acid wash the pool said NO WAY IS IT THE INTERIOR!

The pool builder has drained the pool and re acid washed the interior early October 2017 and now the problem seems to be worse?

I have been told that no one has ever seen or heard of this before, has anyone else had or heard of this issue?
Click to expand...
 
Welcome to TFP! Good to have you here :)

Low pH is likely stipulated because that reduces the likelihood of copper staining arising from the high copper level. You could switch to chlorinating liquid or a salt water chlorinator which would stop the copper level from getting any worse. At some point, you'll be replacing water to get the copper down to a safer level with respect to staining, although you may be stuck between a rock and a hard place - need copper for algae control, but too much causes surface damage and other problems. Chlorinating liquid or a salt water chlorinator would make that problem go away, and is not so finicky. Note that chlorine is the newer, safer, more reliable sanitiser, while copper and silver are ancient methods.

I would definitely look harder for hydrochloric acid (aka muriatic acid, MA). It is used widely for masonry (acid washing) and for cleaning prior to painting. You may find it around the paint section of a hardware store, or around cements, mortars, ready-mix and the like.

+1 to leaving TA alone. Definitely stop adding baking soda (aka Alkalinity Up) and let your TA level settle wherever your acid additions take it. That will slow the pace of pH rise. For bather comfort, don't adjust pH any lower than 7.2
 

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needsajet said:
Welcome to TFP! Good to have you here :)

Low pH is likely stipulated because that reduces the likelihood of copper staining arising from the high copper level. You could switch to chlorinating liquid or a salt water chlorinator which would stop the copper level from getting any worse. At some point, you'll be replacing water to get the copper down to a safer level with respect to staining, although you may be stuck between a rock and a hard place - need copper for algae control, but too much causes surface damage and other problems. Chlorinating liquid or a salt water chlorinator would make that problem go away, and is not so finicky. Note that chlorine is the newer, safer, more reliable sanitiser, while copper and silver are ancient methods.

I would definitely look harder for hydrochloric acid (aka muriatic acid, MA). It is used widely for masonry (acid washing) and for cleaning prior to painting. You may find it around the paint section of a hardware store, or around cements, mortars, ready-mix and the like.

+1 to leaving TA alone. Definitely stop adding baking soda (aka Alkalinity Up) and let your TA level settle wherever your acid additions take it. That will slow the pace of pH rise. For bather comfort, don't adjust pH any lower than 7.2
Click to expand...


Thanks, Needsajet!

I would like to try muriatic acid, but this is not available for sale in Singapore. I think it may be classified as a controlled substance.
For the ES3 system, we have to maintain copper at a certain level recommended by the manufacturer.
What I find is that if I add sodium bicarb slowly ... in smaller amounts at a go, then I get less precipitation.
But I am also taking the advice of not adding any more bicarbs. My TA is probably close to zero by now, given the acids I add in all the time!
We'll see. My borax shipment got held up, so I'm not able to see what happens with borax for now.

If this still does not work, I may give up on the ES3 system ... having run it for two years, I find that I am not using less chemicals but more!
So I may switch back to chlorine. It could be that cyanuric acid helps to stabilise pH? Not sure. Previously when it was chlorinated, I had a pool guy do the maintenance. But I was unhappy with the scum line that developed, and I was attracted to the "no-chlorine" pitch.


David
 
Well, I don't have a scum line on my pool ;)

There's a couple things you've mentioned that are off a bit. I think a couple of very short readings will be very helpful for you. I'll link them. An example is that it's highly unlikely your TA will ever be zero, unless pH is 'off the charts' low. CYA has almost no influence on anything but chlorine. An exception is very long term use of solid chlorine products which all contain CYA as well as chlorine - (pucks, powder or tablets) - that will depress TA over time, and pH sooner.

TFPC for Beginners
Pool School - ABCs of Pool Water Chemistry

These are kinda like 'must-reads' for TFPers.

Also, hold off on adding borates as the last thing after everything else is going well.
 
Needsajet:

May I ask your advice on my next steps.
For the past several weeks, I have stopped adding sodium bicarbonate. My TA is less than 10, if not very close to zero.
But my pH is now much more stable. My weekly regime is to add about 500gm of dry acid (sodium bisulphate). This drops the pH from about 7.8 to about 7.3.
The pH starts to rise immediately, but slowly. By the end of 7 days, it is up close to 7.8 again, and I repeat the acid.
I am not using Borax - have not added any, and there is none in the water (I tested, best I could with the Borax strips).

My question is this: with TA close to zero, is this sustainable? I've read that low TA can lead to other problems like plaster etching (I have tiled pool, but would this cause problems for the grouting between the tiles?), staining (my pool already has some black stains, but I can live with it), and metal corrosion ... I only have a step letter and some light fittings ... the fittings are pretty rusted, but I haven't changed them. The latter is OK.

So should I still consider Borax, together with sodium bicarbonate to raise the TA?
You had said to use Borax as a last resort. What are your reservations about using Borax?

Many thanks.

David
 
Borates are just one more thing to measure is all, and usually not added until everything is well understood and predictable. But good if you need to slow down pH rise because adding acid is happening too often for the rest of your life.

TA at 10 is not a good idea. There's not enough protection from a fast pH drop, which could be low enough to hurt equipment. In the meantime, it's dissolving/etching any cementitious material (plaster or grout) quicker than normal. I would raise TA to at least 40, and preferably 50 and see how it goes. Take a look at Pool Math and see what set of numbers keep your CSI between -0.3 and 0.0

At TA of 10, pH is normally lower than you're seeing, so just to double-check... it's a 25 ml sample, each drop = 10 ppm TA... or 10 ml sample, each drop = 25 ppm TA.
 
Thanks, will try.

needsajet said:
Borates are just one more thing to measure is all, and usually not added until everything is well understood and predictable. But good if you need to slow down pH rise because adding acid is happening too often for the rest of your life.

TA at 10 is not a good idea. There's not enough protection from a fast pH drop, which could be low enough to hurt equipment. In the meantime, it's dissolving/etching any cementitious material (plaster or grout) quicker than normal. I would raise TA to at least 40, and preferably 50 and see how it goes. Take a look at Pool Math and see what set of numbers keep your CSI between -0.3 and 0.0

At TA of 10, pH is normally lower than you're seeing, so just to double-check... it's a 25 ml sample, each drop = 10 ppm TA... or 10 ml sample, each drop = 25 ppm TA.
Click to expand...
 
I've ordered my borax.
From the pool calculator, I will need about 14 boxes of borax to get to 40ppm.
How should I add it? all in one go, or over several days?

And should I raise TA first? Adding sodium bicarb will raise pH. So do I need to have pH at 7.4 before I add borax?

Thanks.
 
Baking soda is a good choice for raising TA and yes, do that first. Note that it does not raise pH very much at all.

You will need acid to go with the borax because that raises pH substantially. Any luck getting hydrochloric acid from a building supply outfit? Long term use of dry acid can cause trouble with grout, concrete, plaster, etc.
 
Tiken, it sounds to me like you are trying to actually run borates at 50 ppm to avoid ph fluctuations, as opposed to using borax to raise the ph.

Just to add to Needsajet's caution:

If you cannot use Muriatic Acid, I'm going to suggest you do NOT use borax but instead use boric acid, which can be obtained at Duda Diesel (DudaDiesel - Biodiesel, Chemical & Solar Supplies, Alternative Energy Store )

- you would have to use waaaay too much sodium bisulphate if using regular borax to push your ph back dwm. The ph swings will precipitate your copper, and exacerbate your situation. Your sulhates, likely already dramatically high, would be seriously worsened by this treatment.

If that wasn't your intent, please ignore my advice.
 
Swampwoman said:
Tiken, it sounds to me like you are trying to actually run borates at 50 ppm to avoid ph fluctuations, as opposed to using borax to raise the ph.

Just to add to Needsajet's caution:

If you cannot use Muriatic Acid, I'm going to suggest you do NOT use borax but instead use boric acid, which can be obtained at Duda Diesel (DudaDiesel - Biodiesel, Chemical & Solar Supplies, Alternative Energy Store )

- you would have to use waaaay too much sodium bisulphate if using regular borax to push your ph back dwm. The ph swings will precipitate your copper, and exacerbate your situation. Your sulhates, likely already dramatically high, would be seriously worsened by this treatment.

If that wasn't your intent, please ignore my advice.
Click to expand...


Yes, I am using borates to avoid pH fluctuations.
But no, I don't have access to many of the chemicals here.
I am now quite worried by your statement, because I have seen what I think is copper sulphate precipitate in the pool - light blue flakes, caking up the ES3 ioniser plates and spilling into the pool at the return vents.
I think pools in Singapore are usually maintained using chlorine products. And perhaps the large public facilities have access to liquid acids. I will try again to obtain some.
I was lucky to find Borax online ... it costs triple to buy, compared to US prices; mostly shipping and markups.
But acids ... that's a no no, I think, because of security concerns.

So if I am stuck with using borax and sodium bicarbonate and sodium bisulphate, what's the best I can do? I think my balance problem was that I was using sodium bicarbonate and sodium bisulphates as well ... one to push TA up (and pH as well) and the other to push pH down. They were just fighting each other, and I was using tons of it. I was hoping borax would enable me to find some equilibrium, once I am done pouring in all the stuff!
 

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