Why do PH-Level recommendations differ so much between US and Europe?

[tors10]

Hello,
i'm new to this forum. I do operate a pool made of fiberglas in Germany. Every manufacturer and also all pool forums in Europe recommend a PH-Level between 7.2 to 7.4 for fiberglass pool.
Most US sources, including TFP, do recommend 7.6 to 7.8.

Why is that?

Thanks in advance for any explanations.
Torsten

 

[PoolGate]

Hello,
i'm new to this forum. I do operate a pool made of fiberglas in Germany. Every manufacturer and also all pool forums in Europe recommend a PH-Level between 7.2 to 7.4 for fiberglass pool.
Most US sources, including TFP, do recommend 7.6 to 7.8.

Why is that?

Thanks in advance for any explanations.
Torsten

Not really, TFP recommends between 7.2 and 8. It is simply a wider range based on maintaining all pool parameters within TFP specs.

PH indicates how acidic or basic the water is. PH should be tested daily at first. Once you gain experience with your pool, less frequent monitoring may be appropriate, depending on your pool’s typical rate of PH change. A PH level of 7.6 to 7.8 is ideal, but really anything between 7.2 and 8.0 is doing fine.

ABC's of Pool Water Chemistry

There are several items things every pool owner should know about swimming pool water. We share details on the basics of Pool Water Chemistry.

www.troublefreepool.com

 

[mgtfp]

It's not really a US vs Europe thing. More a difference between traditional pool industry and science based pool care.

The traditional recommendation to keep pH below 7.6 comes from the (correct) fact that the higher the pH, the lower the HOCl concentration.

At pH 7.5 there is about a 50/50 split between HOCl and OCl-.

Without CYA (stabiliser) in the water, the HOCl concentration drops by about 50% from pH 7.5 to pH 8.0.

With CYA, most of the chlorine binds to CYA where it is protected from UV, but also useless as a sanitizer and oxidizer, but still shows as FC in testing. Therefore, FC needs to be adjusted to the CYA level, this is what TFP's recommended FC/CYA Levels are about. Once this correction has been done, you have the advantage that from pH 7.5 to pH 8.0 the HOCl concentration decreases by only about 15%. Understanding both these effects allows to accept that pH usually (with proper TA management, i.e. allowing TA to settle around 70ppm) likes to stabilise somewhere around 7.8-8.0.

Rather than fighting the constant pH rise due to carbon dioxide outgassing (the carbonate buffer system used in pools leads to overcarbonated water, like soda water) when trying to maintain pH in the lower 7s, TFP accepts to just leave it a bit higher, if that's where pH likes to be in a pool.

Regulations for public pools in Germany/Europe are a bit different to the US and Australia. Public pools are maintained without CYA, and FC levels are to be maintained between 0.3 and 0.6ppm. With the proper automated test and dose equipment, these are perfect parameters, and without CYA, keeping pH below 7.6 does make sense.

To put things into relation: FC 0.6 ppm without CYA is in terms of HOCl concentration just under TFP's recommended SLAM level (used to clear an algae infested pool), which is 40% of the CYA level (e.g. FC 20ppm with CYA 50ppm) - this has about the same HOCl concentration as FC 0.64ppm with no CYA at pH 7.5.

Residential backyard pools are different. I assume that Trichlor pucks or Dichlor "shock" are also around in Germany and in use, and pool water will therefore contain CYA. Proper stabilisation with CYA (ideally adding straight CYA and only using liquid chlorine rather than risking creeping up CYA levels by using stabilised chlorine products) makes residential pool maintenance easy and affordable without having to micromanage. But it requires consideration of the FC/CYA relationship.

Regulations for public pools in the US and Australia are different. Public pools are usually also maintained with CYA. But the regulations don't consider maintenance of proper FC/CYA ratios (or only very vaguely), but define barn gate type limits for both. This can lead to either grossly over-chlorinated water (like FC 4ppm with no CYA), or disgustingly under-chlorinated water (like FC 1ppm with CYA 80ppm).

There has been some movement lately, mainly driven by Richard Falk, who had been a main technical contributor on TFP for many years as Chem Geek. But the industry is very resistant to change.

 

[tors10]

many thanks for your really detailed answer, now everything seems to make more sense for me.

I'm operating my pool with automatic liquid chlorine dosing and for shock, im using also anorganic Calcium Hypochloride. In Germany, one can not buy straight CYA, so to gain a proper CYA level, it seems I have to buy organic trichlor tablets...

Best, Torsten

 

[AUSpool]

A pH of 7.2 - 7.4 for fibreglass seems to be very common, not just from the fibreglass pool manufacturers but also from equipment and chemical manufacturers. But I have never found any sound reasoning for these tight limits. Sorry I’m not being much help, answering a question with a question that no-one appears to have an answer for.

Given the commonly accepted industry FC range of 1-3ppm and the fibreglass pH range of 7.2-7.4 I read an account from a fibreglass pool owner with breaching damage who had diligently followed the manufacturers set targets of 1ppm FC with a pH of 7.2. If minimizing hypochlorous acid is the goal then both targets seem counterproductive. Limiting FC to 1ppm does limit the concentration of hypochlorous acid but running at a pH of 7.2 maximises it at that 1ppm.

 

[mgtfp]

Quite curious how your pool maintenance is going without CYA, which FC levels you are targeting and how to keep them in range.

I'm quite interested in what's happing in Germany and the rest of the EU. Residential pools beyond a little toddler blow up thing used to be quite rare, but that seems to be changing. Germany's regulations seem to have gone down the path of banning CYA. And from what I have seen over there, this seems to be working quite well in public pool environments.

Are there any guidelines for residents pools? In my opinion, maintaining a residential outdoor pool without CYA is quite a challenge. Keeping the appropriate FC levels between 0.3 and 0.6 through frequently changing UV exposures and having the required residual to cope with a few kids emptying their bladders, can't be easy.

When used in moderation, acknowledging the chemical equilibriums in the chlorinated cyanurates system, CYA is actually a great tool for backyard pool maintenance, allowing maintenance of safe HOCl levels without feeling harsh, but still having a decent chlorine reservoir bound to CYA.

If you have some information on guidelines and what pool stores recommend pool owners to do, that would actually help us to understand where the few pool owners from Europe that land here are coming from, and how to best help them when things aren't going great.

 

[tors10]

Since Covid-19, residential pools became quite common in Germany... ;-)
I must correct my previous answer, there is no ban of CYA in Germany... but as most of the pool ownser use organic chloride tabletts, there seems to be no demand for CYA. After a little more Googling, I've found two products under the name "Chlorine Stabilizer"... like Stabilochloran, which contains Isocyanur-Acid.

There is a ban in Germany of selling Calcium Hypo Chloride to private customers, but one can easily buy it on french online stores, they legally deliver also to Germany (EU regulations breaking Country regulations is sometimes annoying and sometimes very funny).

Here in Germany, none of the companies, who sell pools, do give you an introduction to pool chemistry beyond putting some Trichloride tablets into the water for desinfection.

But, on the other side, we have really cool water analyzers... like these here: Photolab, and they are not really expensive (200€).

We also have forums for pool maintenance (most common: poolpowershop-forum ), but they are "far away" from the scientific basis of TFP).
They always give you some advice about chemistry levels, but they totally ignore the dependencies of the levels.
Normal recommendations is:
PH between 7.2 to 7.4
TA between 80 to 120
Chlorine sometimes 1, sometimes 3
Normally no recommendations for Calcium Hardness
And never any really good explanation how these levels depend on each other

I had brown spots in my fiberglass pool. My pool company said: these are metal spots, they come from a not working electrical grounding of the pool (which seems to be really a problem of fiberglass pools).
We also have here a really "soft" tap water, Calcium Hardness (46) and TA Levels (40) are really low.
So I bought Metal Spot Remover, but it had no effect at all (besides completely destabilizing PH and Chlorine levels).
Only solutions was to use muriatic acid gel.

These problems were my motivation to search for pool chemistry explanations and searching for LSI led me to TFP. I will now follow the recommendations

 

[PoolStored]

But, on the other side, we have really cool water analyzers... like these here: Photolab, and they are not really expensive (200€).

I will now follow the recommendations

Here are the test kits we recommend...link-->Test Kits Compared

There are many issues with the photometric test kits with respect to accuracy and repeatability.

You can order the K2006 from Spain:

Taylor K-2006 multiparametric analyzer test kit

• High precision test.• Chlorine determination by DPD-FAS method• Determines up to 8 water parameters.• High quality reagents.• Supplied in a plastic case.

piscinasyproductos.es

 

[AUSpool]

I have a PoolLab paper weight. Not really impressed with it when compared to my K2006C. You need to careful with the volumes and care of the vial. The chemistry is the same as any standard colourmetric test, the difference is that the device now makes the optical assessment with applied conversion factor instead of the human eye. Nothing beats a good titration test. But you have to use what you can get.

 

[mgtfp]

Thanks for the link to that German forum. There is a blog about DIN 16713-3 for pools for private use:

Unser Poolwasser - DIN EN 16713-3 Schwimmbäder für die private Nutzung - Poolpowershop Forum

Unser Poolwasser - DIN EN 16713-3 Schwimmbäder für die private Nutzung O. g. europäische DIN Norm steht uns seit Februar 2016 zur Verfügung.Was ist eine DIN Norm? DIN – Normen sind Empfehlungen. Das heißt man kann sie anwenden – muss es aber nicht.…

www.poolpowershop-forum.de

Wow. Quite some bad information. For example:

g.) Freies Chlor in Verbindung mit Cyanursäure

Neben den o. g. genannten anorganischen Chlorprodukten gibt es organische Chlorprodukte (Bestandteile wie Natriumdichlorisocyanuratdihydrat, Symclosen) in Form von Tabs und Granulat z. B. von den Firmen Bayrol, Ultrapool und Cristal. Diese haben den Vorteil das sie gegenüber den anorganischen Produkten eine Depotwirkung besitzen und die desinfizierenden Bestandteile des Chlores langsamer und über einen längeren Zeitraum abgeben. Um dies zu erreichen wird dem organischen Chlor Cyanursäure zugesetzt. Diese hat allerdings die Eigenschaft das sie sich im Poolwasser immer mehr anreichert und die Wirksamkeit des freien aktiv wirkenden Chlores einschränkt.

Cyanursäurekonzentration im Poolwasser Anteil des freien aktiv wirksamen Chlores

30 mg/l ca. 45%
50 mg/l ca. 33%
70 mg/l ca. 28%
90 mg/l ca. 14%
100 mg/l ca. 12%

Die Cyanursäurekonzentration kann z. B. mit den Pooltestern Scuba 2 oder PoolLab 1.0 gemessen werden.

Was bedeutet das für uns?

Wir haben mit unserem Pooltester z. B. eine Cyanursäurekonzentration von 50 mg/l gemessen. Weiterhin bestimmen wir mit unserem Pooltester den Wert des freien Chlores. Wir messen z. B. einen Wert von 1 mg/l. Bei einem Cyanursäurewert von 50 mg/l wirken aber nur noch 33% davon. Damit ergibt sich für uns ein Wert von 0,33 mg/l an wirklich aktivem freien Chlor welches zur Pooldesinfektion zur Verfügung steht. Um auf einen Wert von 0,6 mg/l an wirklich aktiven freien Chlor zu kommen, müssen wir nun den Chlorwert auf 1,8 mg/l dosieren!

That table is pretty much wrong by a factor of 10. When calculating this with Chem Geek's spreadsheet:

https://www.troublefreepool.com/~richardfalk/pool/PoolEquations.xls

...that is based on O'Brien's equilibrium parameters for the chlorine-CYA system:

Equilibria in Aqueous Solutions of Chlorinated Isocyanurate

...then I get these values (at pH 7.5):



That means to get the equivalent to FC 0.6ppm without CYA, you need to dose to FC 18.9ppm with CYA 50ppm. Not 1.8ppm - that would actually be equivalent to about FC of 0.03ppm without CYA.

Here is a good presentation from Richard about some of the background and the consequences on pool sanitation:

Richard Falk’s presentation on Risk of illness in stabilized chlorine pools - PWTAG - The Pool Water Treatment Advisory Group

www.pwtag.org

Or full-on here:

Assessing the Impact of Cyanuric Acid on Bather’s Risk of Gastrointestinal Illness at Swimming Pools

Current regulatory codes for swimming pool disinfection separately regulate free chlorine (FC) and cyanuric acid (CYA). It is well-known that CYA affects disinfection rates by reversibly binding to FC in aqueous solutions. However, limits for these regulated parameters have neither...

www.mdpi.com

 

[tors10]

Thanks for the link to that German forum. There is a blog about DIN 16713-3 for pools for private use:

Unser Poolwasser - DIN EN 16713-3 Schwimmbäder für die private Nutzung - Poolpowershop Forum

Unser Poolwasser - DIN EN 16713-3 Schwimmbäder für die private Nutzung O. g. europäische DIN Norm steht uns seit Februar 2016 zur Verfügung.Was ist eine DIN Norm? DIN – Normen sind Empfehlungen. Das heißt man kann sie anwenden – muss es aber nicht.…

www.poolpowershop-forum.de

Wow. Quite some bad information. For example:

some pages later they tell you the true story that pool water always gets "agressive" after some time due to ph-Minus, flocking (they do recommend flocking), and low alkanlinity levels.
But then on the last page they tell you that the only solution is to add fresh water.

No words about increasing alkalinity or calcium hardness or ph...

 

[mgtfp]

The main issue is that they recommend "pH minus" to lower pH, which adds sulphates to the pool. These do accumulate in the water and create a corrosive environment for plaster surfaces and metal, also quite bad for the coating of SWG plates, and they can, in combination with high calcium levels, lead to calcium sulphate scale formation. When using pH minus products on a regular basis, then a water exchange from time to time may not be a bad thing.

The best option for lowering pH in pools is hydrochloric acid (or muriatic acid, as it's called in the US, which by the way means the same as the German "Salzsäure", from Latin muria for brine), which only adds hydrogen ions and chloride, which is what added chlorine turns eventually into anyway.

Not sure if HCl is banned in Germany for private use. There is a lot of scare information around hydrochloric acid, especially about the fumes. These are unpleasant, yes, so don't breathe them in. I think they are actually a good thing, because they make you treat the acid with respect and stop you from becoming complacent. They trigger a natural body reaction that stops you from inhaling too much. Always wear eye protection, splashes into the eyes are the only real risk that I see. I don't consider gloves necessary, splashes on the hands you just rinse off in the pool. And don't store it in the garage, the fumes escaping from the vented bottles are corrosive to metals nearby.

 

[tors10]

In Germany, you do get muriatic acid as pH minus, but it is only allowed for pools using chlorine-free desinfection systems... it is said, not because of the fumes of muriatic acid, but instead to prevent the possible formation of chlorine gas, especially with automatice dosage systems because the dosing valves are installed typically close to each other...

So, you are obliged to use sulphuric acid, with the consequences you mentioned.. :-(

 

[mgtfp]

In Germany, you do get muriatic acid as pH minus, but it is only allowed for pools using chlorine-free desinfection systems... it is said, not because of the fumes of muriatic acid, but instead to prevent the possible formation of chlorine gas, especially with automatice dosage systems because the dosing valves are installed typically close to each other...

So, you are obliged to use sulphuric acid, with the consequences you mentioned.. :-(

Yes, it is a very bad idea to mix muriatic acid directly with liquid chlorine. To do that would be extremely dangerous. But so is mixing sulphuric acid with liquid chlorine.

The formation of chlorine gas comes from reducing the pH (by a lot), not from anything in particular that muriatic acid does that I am aware of. You just don't mix liquid chlorine with any acid.

To me that sounds like over-regulation that doesn't make any sense. Wondering if @JoyfulNoise has more insight?

 

[JoyfulNoise]

Over regulation and no understanding of chemistry. As you say, adding ANY acid (even vinegar) to liquid chlorine, will liberate chlorine gas simply from the equilibrium shift of chlorine dissolved in water. Also, sulfuric acid is infinitely more dangerous than HCl because it is incredibly reactive with organic compounds. Sulfuric acid can cause instant deep tissue burns when exposed to human skin. HCl does not. Just mix sulfuric acid and sugar and watch what happens …

 

[mgtfp]

Our bleach bottle in the laundry says "May give off dangerous gas if mixed with other products" and "Mix with water only". Which is concise advice to the point. Don't go into details which liquid (apart from water) you can mix bleach with, just don't mix it.

I don't want to know how many people have tried to remove mould and scale in their shower at the same time. Very bad idea. A couple of years ago, Metro Melbourne had a great add campaign, I think they should have added this: