Jump to content

Heard Today That A Ph Of 7.0 Is Neutral.


Recommended Posts

I met with a PoolSan rep today and he showed me a commercial pool run on PoolSan (Copper and metal ion system). They have had the pool on Poolsan for 1 1/2 years. The pool looks great and no problems so far. However I asked if they ever put in any calcium when they refilled and the rep looked very worried when I told him the gunite pools need calcium otherwise plaster will get damaged.

but ok these are the sort of reading they had in the log book..

pH: 6.8 - 7.2

I was told TA was 80ppm which I figured must be right cause they said they hardly use acid and the pH is fairly stable around 6.8-7.2

They keep pH low to prevent any possible staining which can occur with copper and metals in the pool. They also don't use to much oxidizer. they use a chlorine free oxidizer.

The rep also said there was tons of evidence linking chlorine pools to cancer.

and he said pH of 7.0 was neutral. I thought that was acidic and bad for plaster?

Link to comment
Share on other sites

A commercial pool that doesn't use any chlorine? Are you sure about that? It is illegal since all state codes for commercial/public (not residential) pools require the use of an EPA-approved disinfectant that keeps a residual in the pool water which means either chlorine, bromine or Baquacil/biguanide/PHMB and these are the only chemical products that have passed EPA DIS/TSS-12 (Nature2 with MPS also passes this, but only at hot spa temperatures). They can supplement with additional products, but they can't have zero of one of these three without being in violation of state codes. Perhaps you should report them to the local health inspector. :o

It is true that a lower pH will help to prevent staining when using metal ions in the pool. According to the PoolSan website, it is composed of copper, zinc, gold, silver, aluminum, manganese, iron and nitrogen. Of these, copper is great at killing and preventing algae while silver is the best of the bunch for killing bacteria BUT does not do so very quickly. It takes silver ion around 10-20 minutes and copper ion around 40 minutes to kill 99% of many heterotrophic bacteria while it takes chlorine at an FC of around 10% of the CYA level less than 1 minute to do the same thing. By the way, in their list, nitrogen is not a metal but is a gas (most of air is nitrogen gas) or an atom/element in another compound.

So while metal ions are possibly being OK to prevent uncontrolled bacterial growth for some bacteria, it may not be fast enough to prevent person-to-person transmission of disease and it isn't fast enough to kill the heartier bacteria nor fast enough at killing viruses. For example, this paper shows that copper ions do a 90% inactivation of Herpes Simplex Virus in 30 minutes at 100-200 ppm, but that is far, far higher in concentration than found in pools (copper is usually < 0.3 ppm in pools). This paper shows that silver ions have virtually no effect on vacciniavirus, adenovirus, VSV, poliovirus, HVJ, but that with herpes simplex virus there is a 5-log kill in 60 minutes (roughly a 90% kill in about 5 minutes), but at over 3200 ppb compared to the usual limit of 20 ppb to prevent silver staining.

PoolSan describes how their system works where they claim that bacteria, viruses, algae and scale get surrounded by the positive charged ions. This is partly true since most cells have a negative surface. However, they claim that these surrounded particles then floc together which of course would not happen by itself since these positive ions would normally repel one another. The principle of coagulating and filtering is a sound one and is the basis of products such as PolyQuat 60 which is marketed as an algaecide, but which also binds to cells in general and tends to clarify the water as well, BUT it does not kill pathogens quickly enough to be deemed a disinfectant.

If they don't have a high Calcium Hardness (CH), then the pH and TA in that pool will eventually result in plaster degradation, but the rate of that process isn't necessarily fast and depends a lot on the quality of the plaster work. It's just taking a big risk.

7.0 is pH neutral, but the pH of human tears averages around 7.5 (see this link or this link) and is why that is what is recommended for pools. Swimmers may find some eye irritation in that commercial pool.

If they aren't using a lot of oxidizer of any sort, then if their bather load is higher people will end up swimming in their own sweat and urine. Doesn't sound very appealing to me.

As far as cancer is concerned, there is some cancer risk from chlorine disinfection by-products and I write about some of that in this post, but in residential situations with the much lower bather load (or in spas with the higher temperature and faster reaction rates and outgassing), the cancer risk is probably on the order of 1 in 10 million or lower. You expose yourself to far higher cancer risks via many other chemical exposures. Now, that said, some high bather load commercial/public pools, especially those not maintained well with supplemental oxidation, may have higher risk rates as I mention in that post.

Richard

Link to comment
Share on other sites

A commercial pool that doesn't use any chlorine? Are you sure about that? It is illegal since all state codes for commercial/public (not residential) pools require the use of an EPA-approved disinfectant that keeps a residual in the pool water which means either chlorine, bromine or Baquacil/biguanide/PHMB and these are the only chemical products that have passed EPA DIS/TSS-12 (Nature2 with MPS also passes this, but only at hot spa temperatures). They can supplement with additional products, but they can't have zero of one of these three without being in violation of state codes. Perhaps you should report them to the local health inspector. :o

It is true that a lower pH will help to prevent staining when using metal ions in the pool. According to the PoolSan website, it is composed of copper, zinc, gold, silver, aluminum, manganese, iron and nitrogen. Of these, copper is great at killing and preventing algae while silver is the best of the bunch for killing bacteria BUT does not do so very quickly. It takes silver ion around 10-20 minutes and copper ion around 40 minutes to kill 99% of many heterotrophic bacteria while it takes chlorine at an FC of around 10% of the CYA level less than 1 minute to do the same thing. By the way, in their list, nitrogen is not a metal but is a gas (most of air is nitrogen gas) or an atom/element in another compound.

So while metal ions are possibly being OK to prevent uncontrolled bacterial growth for some bacteria, it may not be fast enough to prevent person-to-person transmission of disease and it isn't fast enough to kill the heartier bacteria nor fast enough at killing viruses. For example, this paper shows that copper ions do a 90% inactivation of Herpes Simplex Virus in 30 minutes at 100-200 ppm, but that is far, far higher in concentration than found in pools (copper is usually < 0.3 ppm in pools). This paper shows that silver ions have virtually no effect on vacciniavirus, adenovirus, VSV, poliovirus, HVJ, but that with herpes simplex virus there is a 5-log kill in 60 minutes (roughly a 90% kill in about 5 minutes), but at over 3200 ppb compared to the usual limit of 20 ppb to prevent silver staining.

PoolSan describes how their system works where they claim that bacteria, viruses, algae and scale get surrounded by the positive charged ions. This is partly true since most cells have a negative surface. However, they claim that these surrounded particles then floc together which of course would not happen by itself since these positive ions would normally repel one another. The principle of coagulating and filtering is a sound one and is the basis of products such as PolyQuat 60 which is marketed as an algaecide, but which also binds to cells in general and tends to clarify the water as well, BUT it does not kill pathogens quickly enough to be deemed a disinfectant.

If they don't have a high Calcium Hardness (CH), then the pH and TA in that pool will eventually result in plaster degradation, but the rate of that process isn't necessarily fast and depends a lot on the quality of the plaster work. It's just taking a big risk.

7.0 is pH neutral, but the pH of human tears averages around 7.5 (see this link or this link) and is why that is what is recommended for pools. Swimmers may find some eye irritation in that commercial pool.

If they aren't using a lot of oxidizer of any sort, then if their bather load is higher people will end up swimming in their own sweat and urine. Doesn't sound very appealing to me.

As far as cancer is concerned, there is some cancer risk from chlorine disinfection by-products and I write about some of that in this post, but in residential situations with the much lower bather load (or in spas with the higher temperature and faster reaction rates and outgassing), the cancer risk is probably on the order of 1 in 10 million or lower. You expose yourself to far higher cancer risks via many other chemical exposures. Now, that said, some high bather load commercial/public pools, especially those not maintained well with supplemental oxidation, may have higher risk rates as I mention in that post.

Richard

Thanks Richard that clears that up! wow!

Ok so this pool is not in the states so there are no laws governing use of disinfectant. This pool is in a private club and in one of the most exclusive gated communities in the islands. Lots of residents have been wanted chlorine free pools and there is a PoolSan rep here in the islands pushing PoolSan. I've been very sceptically that it works. I prefer the BBB method.

I was invited to see this pool and how it was maintained. I asked a lot of questions and one was if they added calcium after they refilled and they hadn't. Even though the surface is Diamond Brite it might fall apart in like 3 years time with no CH in the water. I've seen a pool like that which was resurfaced 3 yrs ago with Diamond Brite and maintained with PoolSan. The pool needs resurfacing as the Diamond Brite is coming off and it is stained black/dark purple like.

I think I will stay away from PoolSan!

btw they want me to test the water for CH. what do you think I will find? If the pool has had no calcium for 1 1/2yrs and the calcium has leaked out of the Diamond Brite won't some CH be then in the water now?

Link to comment
Share on other sites

btw they want me to test the water for CH. what do you think I will find? If the pool has had no calcium for 1 1/2yrs and the calcium has leaked out of the Diamond Brite won't some CH be then in the water now?

If the calcium carbonate in plaster is dissolving into the water due to a lack of saturation (i.e. very negative saturation index, especially with lower pH), then you are correct that this will increase the Calcium Hardness (CH) as well as the pH and Total Alkalinity (TA) with the latter two just as if you had added a pH Up product since that is sodium carbonate. So yes, if you find that over time the CH is rising, then this could be from the dissolving of plaster (DiamondBrite) surfaces. However, evaporation and refill can also increase CH since this adds to the pool water whatever is in the fill water.

At any rate, if you measure the full water chemistry that will give you a snapshot of the current tendency towards dissolving calcium carbonate (with negative saturation index) vs. scaling (with positive saturation index). It will not tell you the rate of how quickly this will occur. The saturation index is a thermodynamic calculation telling you what is possible, not how quickly it will happen.

Link to comment
Share on other sites

btw they want me to test the water for CH. what do you think I will find? If the pool has had no calcium for 1 1/2yrs and the calcium has leaked out of the Diamond Brite won't some CH be then in the water now?

If the calcium carbonate in plaster is dissolving into the water due to a lack of saturation (i.e. very negative saturation index, especially with lower pH), then you are correct that this will increase the Calcium Hardness (CH) as well as the pH and Total Alkalinity (TA) with the latter two just as if you had added a pH Up product since that is sodium carbonate. So yes, if you find that over time the CH is rising, then this could be from the dissolving of plaster (DiamondBrite) surfaces. However, evaporation and refill can also increase CH since this adds to the pool water whatever is in the fill water.

At any rate, if you measure the full water chemistry that will give you a snapshot of the current tendency towards dissolving calcium carbonate (with negative saturation index) vs. scaling (with positive saturation index). It will not tell you the rate of how quickly this will occur. The saturation index is a thermodynamic calculation telling you what is possible, not how quickly it will happen.

Thanks. B)

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Unfortunately, your content contains terms that we do not allow. Please edit your content to remove the highlighted words below.
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...