Public pool sanitation requirements in the UK

[3dogowner]

I apologize if this is in the wrong forum.

Moved to the deep end, which is a better place for it. JasonLion

My sister in has joined a "club" in south eastern England with a pool that is proud to use only "copper and silver" to sanitize their indoor pool.

Directly from their web page: "...we do not use harsh chemicals like chlorine. The water is purified using a natural system of silver and copper, its just like swimming in natural spring water. There are no chemical smells and the water is gentle for your skin and hair (even if its not completely natural) as well as being environmentally friendly. The chemical free water is so natural it can be used to irrigate the vegetables in the walled garden for use in our restaurant."

I'm pretty sure I wouldn't swim in it as I wouldn't trust it to be sanitized.
Does anyone know what the UK requirements are in general for their public pools?

 

[chem geek]

As noted in this page of the Pool Water Treatment Advisory Group (PWTAG), "While drinking water and even coastal waters are subject to regulation in the UK, there is no equivalent specific regulation for the control of swimming pool water quality." The PWTAG has published a Code of Practice (CoP), but there is no legal requirement to follow it. The CoP says in section 5.6.5: "A wide range of disinfectants is available commercially. This CoP uses hypochlorite as a model for disinfection procedures. This is the commonest disinfectant, especially in public pools. But the CoP does not intend to rule out the use of other disinfectant systems, including those that may be developed in the future."

 

[freetime]

" While drinking water and even coastal waters are subject to regulation in the UK, there is no equivalent specific regulation for the control of swimming pool water quality." The PWTAG has published a Code of Practice (CoP), but there is no legal requirement to follow it.

Much 'regulation' in the UK is not legally binding but evidence of compliance with certain published standards can be used as a statutory defense against legal liability. The PWTAG COP is referenced by HSG179 so I expect it would fall in this category.

There is no mandated UK wide system of routine oversight of public pools however environmental health officers do have powers to inspect and take samples for analysis. Response to infection incidents (e.g. Cryptosopridium) is relatively robust - UK public health surveillance is integral to the universal coverage government healthcare system (NHS) which helps to ensure even very small outbreaks (3-4 cases) routinely get picked up. Also the UK obsession with all things 'elf and safety' borders on ridiculous, to the extent that it has inspired a TV sitcom and a 'myth-busters' section on the HSE website!

The ubiquitous 'leisure center' swimming pools where English families take the kids swimming are sometimes a little antiquated but (most!) are relatively well managed and the water is effectively sanitized - perhaps not quite up to TFP standards but never cloudy or off color! These pools are owned by local government (district council) or sometimes charitable groups - organisations which tend to be risk averse and very hot on compliance. Leisure center pools typically have monthly plate counts, sanitizer residuals are checked 3 times a day and it's not unusual for pools to shut regularly due to minor contamination incidents, generally these things get taken very seriously. So perhaps the lack of regulation in the UK stems from the fact that most pools are operated in the public sector, which does a reasonable job of policing itself due to internal culture of safety and public health protection.

However, commercial pools i.e. clubs/spas/holiday parks are an entirely different matter, maintenance and sanitization standards vary from best to worst!

Regarding the club pool in the OP - I would be asking to see bacteriological test results. Perhaps also worth a call to the local Environmental Heath Dept expressing concern to encourage them to 'pay a visit'

 

[freetime]

As noted in this page of the Pool Water Treatment Advisory Group (PWTAG)

Richard

Interesting to note that the PWTAG guidance does seem to indirectly acknowledge the need to increase CL in line with CYA, albeit by specifying a range for each:

11.4.3 Free chlorine levels above 3mg/l should not be necessary in any pool. If this is exceeded,
dosing should be reduced.

11.4.5 The same principle applies to pools on chloroisocyanurates (or with cyanurates added as a
chlorine stabiliser), bearing in mind that chlorine residuals of up to 5mg/l may be necessary in
normal operation. (normal UK range is 0.5 - 1ppm)
For pool using chlorinated isocyanurates as disinfectant, free chlorine should be maintained at
2.5-5mg/l and the cyanuric acid at 50-100mg/l.

 

[chem geek]

Even in the U.S. many regs now refer to different chlorine levels when CYA is absent vs. present, though like the recommendations in the CDC Model Aquatic Health Code (MAHC):

5.7.3.1.1.2.1 Not Using Cyanuric Acid
AQUATIC VENUES not using cyanuric acid shall maintain a minimum FAC concentration of 1.0 PPM (MG/L).

5.7.3.1.1.2.2 Using Cyanuric Acid
AQUATIC VENUES using cyanuric acid shall maintain a minimum FAC concentration of 2.0 PPM (MG/L).

However, there is still no concept of the FC/CYA ratio being proportional to the level of disinfection.

 

[freetime]

However, there is still no concept of the FC/CYA ratio being proportional to the level of disinfection.

I took the liberty of putting the PWTAG numbers through your spreadsheet to see where HOCl falls out :

(@ pH7.4)

CYA FC HOCl

50 2.5 0.021

100 5 0.021

HOCl 0.021 is about double the absolute minimum 0.011 required for sanitisation - although this is at the low end I guess the buffered CL reserve allows a lower absolute HOCl to be effective for localized disinfection and it's consistent with treatment practice in Northern Europe i.e. minimum chlorination + supplemental treatment (Floc/Ozone/UV). As a slight aside, in my experience Southern Europe is a whole different place, where pool sanitation seems to involve very large quantities of chlorine and not much else.


However as with US standards the PWTAG CoP doesn't show the proportional relationship between CYA/FC - with the ranges reversed at CYA 100 the HOCl falls just out of range :

(@ pH7.4)

CYA FC HOCl

50 5 0.045

100 2.5 0.01 - less than 0.011ppm minimum for sanitisation



But PWTAG specify pH range of 7.2 - 7.4 so I tried again with lower pH and HOCl falls back into line....just

(@ pH7.2)

CYA FC HCOl

100 2.5 0.11


It looks like there is a sound rationale behind the individual ranges specified - but as usual the effect of interactions between parameters (FC/CYA/pH) to disinfection seems to have been been ignored. To be fair to PWTAG the HOCl result looks close enough to be within margin of error, a pool with CYA 100 is less likely to have much pH up-drift and I think the simplification is most likely done for ease of understanding by pool operators, which is no bad thing in itself.

This has got me curious to explore the reason(s) that such differing treatment practice has evolved between regions e.g. Europe/USA, but maybe that deserves a new thread

 

[chem geek]

By the way, the 0.011 ppm minimum for sanitation in the spreadsheet is to prevent uncontrolled bacterial growth for common relatively easy-to-kill fecal bacteria. It is not for preventing person-to-person transmission of disease. The EPA DIS/TSS-12 level is around 0.4 ppm FC with no CYA at pH 7.5 so an HOCl level of around 0.2 ppm. That would be roughly an FC/CYA ratio of 31%. Likewise the DIN 19643 standard in Europe is roughly a similar level.

I think the EPA and DIN levels are higher than necessary, but where exactly to draw the line is hard to say. There are lots of pools with CYA and relatively low HOCl levels and generally they don't have outbreaks so if there is person-to-person transmission of disease it's at a low enough level to not get reported regularly. The protozoan oocyst Cryptosporidium parvum is an exception but that's because it is highly chlorine resistant (the oocyst has a difficult to penetrate shell). I generally say that an FC/CYA ratio of 20% would be reasonable for commercial/public pools though even 10% might be good enough and either one would be enough to prevent green and black algae (the 20% would be more than enough to prevent yellow/mustard algae as well).

 

[freetime]

By the way, the 0.011 ppm minimum for sanitation in the spreadsheet is to prevent uncontrolled bacterial growth for common relatively easy-to-kill fecal bacteria. It is not for preventing person-to-person transmission of disease. The EPA DIS/TSS-12 level is around 0.4 ppm FC with no CYA at pH 7.5 so an HOCl level of around 0.2 ppm.

Thanks for the clarification - so the PWTAG recommended minimum of 0.5ppm FC at <pH7.4 with no CYA is conservative against EPA DIS/TSS-12

That would be roughly an FC/CYA ratio of 31%. Likewise the DIN 19643 standard in Europe is roughly a similar level. There are lots of pools with CYA and relatively low HOCl levels and generally they don't have outbreaks so if there is person-to-person transmission of disease it's at a low enough level to not get reported regularly.

On the other hand where CYA is used the PWTAG minimum levels equate to FC/CYA ratio of just 5% which seems to be very low by comparison.

In reality most all public pools in the UK are indoors - those few that are outside don't get too much sun - so there are probably not many public pools in the UK using CYA anyhow. I'm just interested to try to understand the basis of the recommended FC/CYA levels, but there doesn't seem to be one.