Recommend me a 20" carbon block filter. I currently use a Pentair CFB-plus. £33 at gapswater. I want something cheaper but just as good. No 💩off eBay please. 👍
You can buy carbon block filters that are cheaper than Fiberdyne from most other suppliers. This is from The Cleaning Warehouse
https://www.ebay.co.uk/itm/193810601488?hash=item2d20031610:g:eRsAAOSwTuxf3Htq This price is for 3 so is roughly a third cheaper per filter. However, the service life they quote is 6000 gallons US which is 24000 litres UK.
It has a disclaimer on the webpage that the service life depends on the level of contaminates in the water which is going to apply to every carbon block filter when you think about it. (Pentair do advise what their service life is based on in their spec sheet.)
If we take the 24000 litre service life as gospel and you change those filters every 24,000 litres, you are going to replace those carbon block filter 3 times to the Fiberdyne's once. I hate changing prefilters.
Doug Atkinson once stated that tests done in one city on the south coast showed no chlorine in the tap water after numerous samples were taken and analysed. He also said a similar situation was found in an area in Scotland where he lives. In cases like these those Fiberdyne filters could well have a much longer service life than the manufacture quotes of 75600 litres.
Over the years some window cleaners have reported only changing their cheap carbon block filters every 6 months with no issue. But that doesn't mean much when you think about it. It could well be that those reporting could just believe that changing an r/o membrane every 2 or 3 years is a normal process in water filtration.
All I know is my own experience with our water supply. I have religiously replaced Fiberdyne carbon block filters on my 4040 every 77,000 litres since I purchased the r/o in July 2012. I am still using the same Axeon HF5 membrane since new. Initially the membrane's rejection rate was 98%, it's now running at 97%.
Maybe our water has a lower chlorine content than the service life of the filter is calculated using. If it is, then my carbon filter will last longer. I don't know, so I will just stick to what the manufacturers advise. Accurate chlorine testers that will identify the minutest chlorine residue are very expensive. Chlorine test kits sold for swimming pool owners aren't sensitive enough for this.
But here is the conundrum. Dry Clean on here once stated that replacing the carbon filters less frequently will save money. It may cause an earlier demise of the membrane, but even replacing a membrane more frequently might still mean reduced filtration costs. He made a very valid comment. It's all about the economies of scale.
As they say in the classics; it's your call.
BTW, Daqua also sell Spectrum carbon block filters. I notice that their quoted service life is 12,000 litres.
The first wfp system I purchased was second hand and a year old from a window cleaner in our town. The r/o was also a year old. The cleaner I purchased the unit from very kindly told me that he had just replaced the prefilters for me. That was the first prefilter change he had done.
Within 6 months I had to replace those membranes as they were producing at a rejection rate of less than 94%. I was using a lot of resin polishing the water off. I continued to use that r/o for a further 6 years with the new membranes and changing prefilters regularly. Same town, same water. So in our town, changing prefilters annually meant the early demise of the membranes due to chlorine contamination.
