OC-1 Filter Media in a Domestic Swimming Pool

The Verdict


Pool size 15 mtr X 4.5 mtr Pool shape Rectangular with Roman steps
Pool type Delifol vinyl liner UK Situation Inground
Capacity 50 cu mtrs Use Occasional seasonal domestic
Pump Certikin Swimflo HPS031M Flow rate at 10 mtr head 8 cu mtr hr
Filter Certikin ZZOC-1/20 Filter Diameter 20"

The Verdict - Would I Recommend OC-1?

The crux of the matter is am I happy with and would I advise others to use OC-1? Bear in mind that I have invested time and money in the filter and media, so naturally I want them to be a success.

The point of a swimming pool filter, and the media within, is to remove debris from the water. It doesn't sanitise or circulate or commit algaecide. In other words to improve water clarity. But how is this to be measured, short of a very expensive turbidity meter? I doubt whether the cheaper turbidity meters are accurate at less than 0.5 NTU, and at under 0.1 NTU I would be suspicious of expensive meters too. (An NTU is a nephelometric turbidity unit, with a general and probably legal requirement that it should be below 0.5 in public pools: this seems a high limit, as a significant depth of water with 0.5 NTU turbidity has visible cloudiness.) For the domestic pool owner it has to be eyesight and perception, with 'Can you see the bottom of the deepest part of the pool clearly?' as a basic and minimum requirement. It's all subjective, as subjective as those testimonials for any product you care to mention.


From the point of evaluating filter media capabilities, we can forget 2020. Undoubtedly progress was made with the manual clearing of the debris on the floor at the deep end, and the removal of the black gunge from the walls and bottom in early 2021. This action has made the greatest effect on water quality. Hopefully others will not be starting from there. I cannot recommend a deep leaf net too highly, I'm going to get another as a spare. Sanitising and balancing the water (I have only used chlorine and pH-) also provides a sound base.

Mid 2021:

I would define the water as clear, but perhaps a little dull. I can certainly see the bottom of the deepest part (about 7') clearly. Using a pint glass comparison sample it matches our drinking water for clarity. At a guess it's under 0.5 NTU, but how far under I couldn't say. And how can I possibly compare it to the sand filter clarity of a few years ago? My wife says it is as clear as it's ever been, but again, this is subjective. A torch shone closely on the water at night shows what appears to be minute suspended solids floating along merrily, but the same test on pool water in a pyrex jug doesn't show any.

I would say that OC-1 has matched the filtering quality of sand so far, and hopefully will surpass it in time. So yes, I would recommend it (with a few caveats) as it does have advantages over sand in other areas. If the filtration reaches anywhere near the one micron claimed, then I would recommend OC-1 very highly indeed. But I'm not there yet. The large slots in the top and bottom laterals, and the open nature of the OC-1, appear to enable much of the water to flow straight through the filter media untouched. I believe that this is why the filtering process seems to be slower than sand, which offers a much denser barrier to water flow. It's a slow process and I am still waiting for that one micron clarity, but I can see improvement little by little, if not quite daily.

The benefits of OC-1 are, as I see them:

1) It will never, ever find its way into the pool
2) Backwashing is less frequent
3) Its open structure lowers resistance to flow
4) It requires no more maintenance than sand
5) It allegedly filters to one micron
6) It can't cake or clog or channel
7) It's light and easy to handle

The cons are few so far:

1) It seems to be slower to reach maximum filtering capability
2) Getting the correct flow though the filter may be difficult
3) Hazy water may be a problem in some cases
4) Nobody, especially in the pool business, knows anything about it, or if they do they look upon you as a crank

I can live with most of these. I believe that OC-1 needs a little more knowledge and attention, and needs a closer adherance to flow rate and other parameters. By mid 2021, after some tribulations peculiar to my pool, I am reasonably happy with the state of the pool water, but I await the day when I need sunglasses to protect my eyes from the scintillating pool water.

I would install the specialist ZZOC-1 filter. The water distribution with top laterals will always be better than a top dispersion adaptor. I would also try to reduce the flow through the filter (it will inevitably be a reduction) to as close to Certikin's recommendation, which in my case with the 20" filter is 5 m³/hr, as possible. The filtering system needs to be in sound working condition.

I would not recommend OC-1 to anyone who is not, for whatever reason, able to spend some time and effort in setting up and managing their pool filtering system. For those who like a bit of a challenge then OC-1 is well worth considering.


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