Thursday, March 13, 2014

Spa Covers Etc. | Liquid Chlorine or Salt Pool

Salt Pool vs. Liquid Chlorine Pool

TDS (Total Dissolved Solids) is a measurement of ALL things that come into contact with the water. When a chemical is added it leaves behind “salts”. When a swimmer swims they sweat just as much as they would if they were running. The difference is that it is all washed away by the water. Sweat is salt. If the wind blows dust into the pool it will add to the TDS. If the birds “drop” into the water this adds th the TDS. And Urine adds to the TDS.
Fresh water is anything <1000 ppm
Saline Solution (eye drops) 15,000 to 30,000 ppm
Sea water is 30,000 to 40,000 ppm
If the TDS is higher than 2500 ppm in a swimming pool we recommend draining the pool.
(In the pool industry we usually get complaints about the pool tasting salty at >5000 ppm)
If the pool has a high concentration of swimmers at one time and the TDS has tested at <2500 ppm, the usual source of the “salty taste” is from sweat floating at the top of the water level. (Sweat doesn’t sink).

Now we compare Liquid Chlorine to a Salt (generator) Pool.
*** Note there are many types of ways to make chlorine. This ONLY compares Liquid Chlorine to a Salt Pool.  Dry Chlorine is very different.

Liquid Chlorine:
In Every gallon of liquid chlorine is a POUND and a HALF of salt. The chlorine manufacturer has a giant storage tank that they use to make liquid chlorine. It uses water and salt NACL. The tank uses a low voltage charge to polarize the NA (sodium) and the CL (Chlorine) using a negative charge the can separate the two elements and make what we call liquid chlorine (Sodium hypochlorite). Notice the Salt and chlorine in the words of sodium hypochlorite?
Over the course of time as more and more chlorine is added, water evaporates leaving the TDS from the tap water behind. When you add more water, more TDS are introduced to the pool. Adding chlorine and other sanitizing chemicals contributes to the rise of TDS.
A commercial pool may need to be drained annually depending on how many people use the pool over a course of the year. Hotter summers will require more chlorine and all will make TDS rise faster.
Fresh water out of the tap (today 9/6/2013) is 486 ppm. At 2500 ppm draining of the water is recommended.

Higher TDS readings are not harmful as long as there is a chlorine reading above 1.0 ppm. Higher TDS readings DO cause the pool to require a bit more chlorine. High TDS may cause cloudiness to the water.

Salt (generator) Pool:
This is exactly the same thing as a liquid chlorinated pool.
The difference is that in a Salt Pool, the owner of the pool owns the salt generator (the machine that makes the chlorine) and your pool is the storage tank.
Initially when the pool is filled, depending on the size of the pool, about 200 to 500 pounds of salt will be added to the water, dissolved, and when the salt generator is turned on it will do the following:
The water in the pool must be circulated (on the customers dime) in order for salt to be introduced as chlorine and mixed throughout the water. Approximately every 4 hours the unit will reverse polarity and separate the NACL into Salt and Chlorine and then reverse and turn itself back into NACL Table Salt. The strength of the chlorine in the water is determined by the setting on the salt generator and the length of time that the pool is running.
Over time more salt will be required and this will add to the TDS.
Neither a freshly filled salt water pool nor a pool that is sanitized using liquid chlorine should have a “salty” taste. However, over time both pools may develop some sort of taste. This usually is when the pool is to be drained. A TDS test can confirm this.
Note**** Do not confuse the above description of a salt pool with a pool filled with salt water. A salt water pool is a relaxation pool in which the salt level is that of the Dead Sea and you actually float on the water. You can’t swim in this type of pool.
Remember Sea Water is over 30,000 ppm. A pool is usually under 5000 ppm.

Now that you know a Salt Pool is the same thing as liquid chlorinated pool you should ask your pool professional about things like the initial cost of a salt generator, annual maintenance costs, how often do you add more salt,  and how long do they last? Compare this to the cost of liquid chlorine (at about $4.00 per gallon) and you can make an educated decision.

For more information visit our website @ Spa Covers Etc. 

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