Tap Water Residual Disinfectants

Hi Folks,

Please first take a look at the following to see the context in which I decided to start this new thread:

https://forums.thinkfish.co.uk/general-fishkeeping-advice/loosing-fish/msg48570/?topicseen#msg48570

I had been looking over the Water Report from my region's Water Supplier when I stumbled across something:

Residual Disinfectant - Free
Residual Disinfectant - Total

As I understand it, the first of these is chlorine. The second of these is chlorine + chloramine. So far, so good. But, then, I looked at the PCV* for each of these and it reads 'No Limit'. Compare this with the USEPA** where the MRDL*** is 4.0 mg/l (measured as Cl₂). In the UK, therefore, it looks like water companies can add as much chlorine or chloramine as they wish. When the likes of Seachem with their Prime product arrive at a recommended dosage, they presumably do this on the basis that the maximum chlorine or chloramine will be 4.0 mg/l. If that's the case, is Prime going to be effective when chlorine or chloramine is in excess of this figure - as permitted in the UK?

I am not a tap water user for my tanks. So, I don't know how many people measure chlorine in their tap/tank(s) water. I do note that test kits are available that measure both free and total chlorine:

https://www.itseurope.co.uk/products/waterworks%E2%84%A2-free-total-chlorine?_pos=1&_sid=cc4cf7321&_ss=r

* Prescribed Concentration or Value
** United States Environmental Protection Agency
*** Maximum Residual Disinfectant Level

So, those are my thoughts on this topic. All feedback very welcome. Let's ensure that we are all in agreement with what I'm proposing before acting on my thoughts. That's all they are at the moment - thoughts. Feel free to rip them to shreds!

JPC

For my own locale, further along the rows for residual disinfectant (free) and (total), there are values of min/med/max, and all are very much under that figure - are there no such columns with such levels in yours, JPC?

Aaah, I see. Yes, for my locale, the PVC column was blank which perhaps also suggests no upper limit, and very similar highest value and very similar number of samples to yours.  (Yep, "that figure" referred to the 4.0 mg/l.)

The WHO has set a maximum of 5ppm. Apparently UK authorities tend to keep it below 1, and usually less than 0.5

http://dwi.defra.gov.uk/consumers/advice-leaflets/chlorine.pdf

Hi @Hampalong

Many thanks for the information and link.

JPC