Measuring Chlorine is Salt Water Pool

[Kalograta]

Hi Pool People

This is a bit of a long story so I'll try and keep it short. I have two pools of my own that use standard chlorine granules for shocks and tablets to maintain levels. I keep an eye on PH, Chlorine and CYA. They run OK most of the time.

A neighbour has asked me to look after their new pool. This is a different type and works with salt in the water and a computer controled chlorine generator. PH is also maintaineed automatically. It has gone repeatedly green...... I have checked the chlorine with my drop tester in it is zero. The guy who installed the pool, assures me that the chlorine in the pool is fine and that it just will not show on my drop test???? I do not believe this. THe guy has treated the pool with some Oxygen based liquid and it has cleared slightly but still zero chlorin and still murky.

My question is, if the installation guy is correct - how do I measeur the chlorine in thisn type of pool.

Thanks for any replies

Nick

[Denniswiseman]

No he isn't correct and you test it in exactly as any other pool with your drop tester. Chlorine is chlorine which ever way it is delivered
Check you have sufficient salt in the pool, they need about 3000ppm to operate corectly
A SWCG should only maintain the chlorine level after you have reached the desired Pool Levels and chlorine
Bearing in mind that it will only produce chlorine while the pump is running. Also the SWCG should be sized for double the rated output for the pool which is 24/7 at 100%
The fact that there has been no chlorine in the water has created an algae bloom and he will need to Slam with relation to the Chlorine / CYA Chart
Best to use liquid chlorine as granules, tablets and pucks put extra CYA in which renders your chlorine ineffective
For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm.
For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm.
For every 10 ppm FC added by Cal-Hypo, it also increases Calcium Hardness (CH) by at least 7 ppm
Liquid chlorine (sodium hypochlorite or plain bleach)
Muriatic acid (hydrochloric acid) to lower pH and TA
Bicarbonate of soda to raise TA
Aeration will raise pH only
Soda ash will raise pH and TA

[Kalograta]

Thank you very much for your comprehensive reply. I have tested the pool with my drop tester and chlorine is still zero. However pool is almost clear. This seems strange to me though, the guy who installed the system ( a plumber, not a pool specialist) has put in about 10 litres of active oxygen. I think this is in fact hydrogen peroxide? I'm not sure what his theory is but surely pool will go green again as soon as effect wears off.

My other thought is of course it might be possible that the chlorine generator is working but cya could be so low that the chlorine produced is disappear by the time I test it?

My next course of action will be to check for cya.

Anyway, thanks again for your input.

Nick