Ideal Salt Level Pool Pilot

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Waterbear,

I did a little further research.

While ORP values are useful values for predicting algae breakouts in aquariums the ORP value for aquariums do not translate to pools, as marine aquariumss are controlled environments (where the temperature, UV, are constant and wind normally plays no part) albeit that higher values can guarantee higher FC chlorine levels. Predicting algae breakouts in pools using marine aquarium guidelines would normally not be of value as other levels such as ammonia, nitrates, nitrites, phosporous, and especially the fact the salt ppm (normally 30,000 to 50,000 ppm) in marine aquariums is many times greater than in a pool. Additionaly chlorine is normally not used in salt water aquariums but Nitrifying bacteria are used, this is not so in salt water pools, see here:

http://en.wikipedia.org/wiki/Aquarium

It seems that two pools with identical ORP values can have different levels of FC, and even these ORP values can fluctuate quite a bit depending on the time of day.

For example an ORP value of 700 in one pool may indicate an FC of 6, while and ORP value of 650 in another may also indicate a FC of 6. Even the same pool can have wildly swinging ORP numbers in the course of one day but still have FC readings of 6 consistently throughout the day.

Obviously as with aquariums the larger the size the less the fluctuation, a 50 gallon tank will fluctuate more than a 500 gallon tank, so it seems this is also true of pools.

I believe that in a post from Chem Geek he stated that ORP value was not as valuable to pool chemistry as once thought and that the HOCL % was a better indicator as far as algae control was concerned. At least that is the way I understood his post. And from practical experience I would have to agree.

The time line of bacterial cross infection between humans is affected by ORP but at levels of 650 or 700 depending on your view, or 750 in a public pool, this is not a concern; at least in regards to algae control. 650 ORP is the current standard for most US public pools, Germany's is 750 but that as you know is extremely hard to achieve without very sophisticated equipment, which most US public pool do not have at present.

Additionally most persons do not have ORP controllers or complicated ozone setups to mitigate the loss of chlorine so for the average person HOCL% would most probably be an easier number to strive for as it can be easily calculated using CyA, pH, and the FC numbers.

It seems therefore that for those with no algae problems a SWG pool would be optimized at pH 7.5, CyA 35, and FC of 4, this gives an approximate HOCL % of 0.050 %, which could be considered a minimum standard. For those with algae issues the FC is better kept at 6, an HOCL % of 0.080%. Obviously if one raises the CyA ppm then one would have to either lower the pH (harder on the eyes while swimming) or raise the FC which most SWG are unable to do as they struggle at FCs of 5 or 6, unless they are oversized.

Any thoughts?