Salt System / Ph Injection

[PoolDoctor]

Hi All,

We will be installing a salt water treatment system shortly, in a residential pool. The pool owner specifically requested the Zodiac Tri with built-in pH injector. Hmn. Where did he learn that we wonder? Turns out, he is an engineer. So, I thought I would post a bit of info here on why a pH injector is also required in a salt water pool.

A salt water treatment system converts via electrolysis the salt [sodium chloride] in the pool water to a gaseous form of hypochloric acid. HA is the killing form of chlorine, and this chlorine gas effectively oxidizes (or sanitizes) any foreign contanimation in the water (e.g., bacteria, viruses, water borne pathogens).

The problem is, this process of converting the salt to chlorine tends to make the pH rise over time (any further explanation here gets VERY technical, beyond the scope of this post). The salt in the water also contributes to the pH drifting upwards. Why is this a problem?

Because, the efficiency (ORP to be exact) of chlorine is inversely related to pH. At high pH levels, ORP (oxidation reduction potential) declines SIGNIFICANTLY. Some estimates are, that at 8.0 ph, chlorine is only oxidizing at 20% potential. This means, even if you have high ABSOLUTE levels of chlorine in the water, that chlorine might only be working at a small fraction of its potential. This problem is further exacerbated by most homeowners not knowing that they need additional chlorine stabilizer in the water (cyuranic acid) to counteract rapid evaporation of chlorine gas. Voila - high pH, and no CYA = problem. This is where 90% of the complaints come from with regards to salt water chlorinators and commercial liquid chlorine pools (liquid chlorine is also un-stabilized).

Lesson - keep the pH down with a pH injector, and stabilize your pool water at 30-50ppm cyuranic acid. End of problem, and very nice high ORP. Safe water!

Gil

[jbrain]

I have a Zodia Tri Ph large installed for almost a year and have no problems.My Ph is a constant 7.3 and my chlorine levels are adequate, however I would like to learn how to check CYA levels once without spending thousands on such a taylor kit.

[PoolDoctor]

I have a Zodia Tri Ph large installed for almost a year and have no problems.My Ph is a constant 7.3 and my chlorine levels are adequate, however I would like to learn how to check CYA levels once without spending thousands on such a taylor kit.

Sounds like the Zodiac is doing its job nicely. You can easily check CYA using inexpensive litmus strips. They check free chlorine, pH, CYA, alkaline, and hardness. Available at any good pool shop that understands chemistry.

Gil

[jbrain]

I have a Zodia Tri Ph large installed for almost a year and have no problems.My Ph is a constant 7.3 and my chlorine levels are adequate, however I would like to learn how to check CYA levels once without spending thousands on such a taylor kit.

Sounds like the Zodiac is doing its job nicely. You can easily check CYA using inexpensive litmus strips. They check free chlorine, pH, CYA, alkaline, and hardness. Available at any good pool shop that understands chemistry.

Gil

Could you point me to such a shop within a 5000 Km radius

Or do you stock the strips ?

[yankee99]

I agree with PD. My ph is constantly slowly rising with my hayword system. A bottle of muriatic acid takes care of it but i hate handling it.