Sarah House gravatar image

Specifications for paints for drinking water tanks?

by Sarah House | 2017-09-13 15:53:36 -0500

Hi everyone,

Does anyone know of any simple to understand (or even not so simple to understand) specifications for paints for the inside of drinking water tanks? I have checked the ISO standards and there does not seem to be any details available here. The UK Water Industry covers this under the The Water Supply (Water Quality) Regulations 2016, 31 (which is not specific about the requirements but talks more about who can certify) and the DWI provides a list of named products, but I can't seem to locate any general guidance on how the certificiation should be made?

If anyone has seen any spec info from any source that would be great. If anyone has any examples of country specs from a low income country even better.

Many thanks

Sarah

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John Cody gravatar image

by John Cody | RedR Experts | 2017-10-07 06:26:03 -0500

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Hi Sara

Is the purpose of the paint water proofing or corrosion protection?

Check out the link for a product for waterproofing the roofs of masonry/concrete tanks. http://resapol.com/wp-content/downloa....

I am not aware of paints specifically for the inside of tanks, and I would not be confident that the above product would be satisfactory under pressures that would be encountered on the walls of a water tanks. In the past bitumen was used in joints but I think this practice is likely to be frowned upon at this point, as I think modern practice would be to provide internal water proofing measures at the construction phase. If you have access to the BSI online there is a section within BS 8110 (Structural use of reinforced concrete) that deals specifically with the design and construction of water retaining structures-http://lms.iesl.lk/pluginfile.php/2331/mod_resource/content/1/8110%20Part%201-1997.pdf. This standard has been superseded by RC Eurocode, but the Provisions of the Eurocode are likely to be broadly similar.

You could try googling "Tanking Products". These products seem to be mainly aimed a damp-proofing basements, and are unlikely to function under the pressures that would be encountered in a reservoir. If the purpose is not water proofing then I think you would ok using a non oil or lead based acrylic paint. If the purpose of the paint is corrosion protection then I think modern practice would be to provide so form of cathodic protection. You could have a look at http://resource.npl.co.uk/docs/scienc... to see if this is a potential solution to your problem.

Hope this helps

John

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Tim Foster gravatar image

by Tim Foster | RedR Experts | 2017-10-06 15:10:54 -0500

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HI Sarah We used what I remember as a two part epoxy paint in Rwanda in the early 1990s for small water tanks. My starting point would be https://www.google.ch/search?q=epoxy+... but guess you have researched well beyond that. Sorry not to be able to be of more use. Good luck.

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Sarah House gravatar image

by Sarah House | 2017-10-18 18:20:01 -0500

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Hi John and Tim and also Graham Welland from Thames Water (who sent me some information directly).

Thanks so much for responding to my email which has been greatly appreciated and apologies for my silence to all of you. Have had a very busy few weeks working and travelling in country, including looking into this issue some more and wanted to have time to respond to your posts properly. Strangely I received John's email in my inbox and tried to send a quick reply of thanks by return of email at the time, but it seems this system does not work as my response was not posted. But for Tim's email I didn't even receive this in my inbox. I am new to Knowledge Point in this format, so not sure if I have the hang of it yet? I need to work that one out.

John thanks very much for the suggestion re cathodic protection and also other forms of waterproofing. We haven't discussed this option as of yet but I will add it into the discussion. I haven’t heard this mentioned but it would be interesting to know if it is a technique already available in country. In terms of the reason that painting is recommended as I understand it, it is for both preventing / slowing down the rusting process for steel tanks and also probably for a degree of waterproofing. I just found this interesting article which talk about various options including different types of epoxy paints in case you are interested: https://www.wwdmag.com/coatings/prote...

Thanks very much Tim for your experience of using epoxy paints in Rwanda. That's also useful to know. I have also just established last week that in the country I am currently working in that epoxy based paints are produced in country (two part mixes) and used by one of the largest water tank manufacturing companies for the insides of water tanks; and also that a producer has also just started producing a bitumous paint. This particular company do their best to identify if the paint is safe for drinking water but there do not seem to be agreed procedures or processes for checking their safety for use in drinking water tanks in country at the moment. Painting inside tanks seems to be quite widely recommended as it is noted in various guidance and regulations, including for bottled water factories. I presume that at present most companies and smaller water tank users (such as water tanker or donkey cart operators) probably do not use such paints as they may not know they need to use a non-toxic paint and also using an epoxy paint apparently costs about 15 times as much as a standard paint off of the shelf so this is also quite a deterrent. Even when a system for certifying paints, sealants or other materials for use with drinking water is established (which seems to be quite complicated and will need sophisticated lab equipment and processes), there will still be significant challenges for enforcement and ensuring use; which I think would be similar challenges faced in many countries.

Graham also very kindly pointed me in the direction of the DWI website (http://www.dwi.gov.uk/drinking-water-...) and their list and procedures for applying for approval testing for paints and also provided a further contact for more details, which is also really helpful and I will probably take up at some point. Both epoxy resin and polyurethane based paints are included on the DWI approved list of site applied coatings for water retaining structures for inert tank materials such as metals and cement based structures (pp48-50).

Thanks so much again for taking the time to respond to my question. It has been much appreciated and I will be sharing the various suggestions when back in country.

Many thanks.

Sarah

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Asked: 2017-09-13 15:53:36 -0500

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