Thread: New Big blue GAC cartridge filter not working?

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Just fitted a brand new big blue cartridge from Amazon (see pic above) for my 20" housing, fitted nice and easily both washers in tact but getting 0.36mg/L Total Chlorine reading from the tap.

Any clues ?
is the cartridge the wrong one?
Do they take time to work?
are some 20 X 41/2 not compatible with different housings?
Is it not seating right in the housing?

The 20" filter serves the whole house then I have a 12" Evolution Aqua inline chlorinator at the outside tap that works perfectly.


love to hear other users experience.

Thanks Shaun.

a 20" GAC serving your whole house will not give you a low level of chlorine,
unless your tap water has virtually no chlorine in it in it.
what is your tap water chlorine level before ther filter?

Those 12" evolution dechlorinators are not brilliant at giving you a very low level of chlorine either.
again being GAC don't last that long for the cost.

0.36mg/L Total chlorine untreated water.
0.00mg/L through evolution dechlorinator.

I was hoping to at least lower background chlorine through whole house using big blue 20” and make life easy for the evolution decorator.

I still use sodium thiosulphate in pond too.

I use these and find them great.

https://aquafilter.com/en/product/3/16/fccbkdf

Full range here:
https://aquafilter.com/en/product/3/inline-carbon

This thread tells you the flow rates and how much capacity they can take before needing replacement:

https://www.koiforum.uk/water-treatm...nfo-ideas.html