Hayward sense and dispense

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ozone generators, UV systems, . . .

Hayward sense and dispense

Postby wlstallings » Thu 19 Feb, 2009 09:26

I would like to know if anyone has used the Hayward sense and dispense for controlling PH? Does it work well and is it worth it?

chem geek
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Hayward sense and dispense

Postby chem geek » Thu 19 Feb, 2009 13:13

You can read what some people say about it here and here. Just keep in mind that if you tend to have a problem with rising pH, then there are other ways of minimizing that problem. If the pool does not have a pool cover, then a high Total Alkalinity (TA) level will tend to make the pH rise, especially if there are sources of aeration (waterfall, spillover, fountain, aeration jets). Saltwater Chlorine Generator (SWG/SWCG) pools also tend to have rising pH both due to increased aeration from hydrogen bubbles and possibly some outgassing of undissolved chlorine gas.

If a pool has new plaster, then the pH tends to rise significantly in the first few months and even up to a year.

So if you are not using acidic sources of chlorine, such as Trichlor, and are instead using hypochlorite sources (e.g. bleach, chlorinating liquid, Cal-Hypo, lithium hypochlorite), then check your TA level. It should not be higher than 80 ppm and could even be a little lower if you compensate with a higher pH and/or Calcium Hardness (CH). A higher TA level is only needed when using acidic sources of chlorine (e.g. Trichlor, Dichlor), accounting for the acidity of chlorine usage/consumption.

You can also use 50 ppm Borates in the pool as an additional pH buffer. This won't change the total amount of acid you need to add, but will let you add it less frequently as it will slow down the rate of pH rise. If you have an SWG pool, then the Borates may lower the acid demand as well since the Borates are a mild algaecide so could let you lower your SWG ontime if the chlorine demand drops due to less nascent algae growth. Also, in an SWG pool the CYA should be higher (60-80 ppm, 70-80 ppm is best) if the pool is exposed to direct sunlight since this will let you turn down the SWG ontime since less chlorine will break down in sunlight. Just be sure to maintain a minimum FC of at least 4.5% of the CYA level for an SWG pool (in a manually dosed pool, the minimum FC is 7.5% of the CYA level).

You can learn more by looking at the Pool School.


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