Manage Salt Cell Life
Cell Design
Salt water sanitising systems have been successfully used for many years with both Domestic and Commercial swimming pools to eliminate or minimise the use of Chlorine chemicals. The purpose of chlorine and other chemicals such as bromine that are added to water that are used by humans is to control and minimise the growth of bacteria. If water born bacteria is not controlled, pool water will go green and smell “off”. Around 15 years ago similar, and much smaller (less costly) systems were developed for use with Spa Pools.
Such systems effectively use the process of electrolysis to produce a form of chlorine in spa water from salt (sodium chloride). This takes place through a controlled voltage being applied by the system controller to electrodes of the systems “salt cell”. This then sits within the Spa water that contains the correct dilution of salt.
However one of the challenges with a Spa Pool, unlike a normal unheated swimming pool is the fact that you are dealing with hot water, and that in such an environment chlorine Sanitiser loss happens fairly quickly. For this reason Salt Water Systems slowly and regularly produce the chlorine sanitiser to keep water free from bacteria, rather than a less often “big hit” or “shock” of chemicals as with non Salt Systems spas. Often times the actual level of chlorine present may be so small, that it does not register on your test strip depending on where you and when you tested.
To address this, different systems enable control of the amount, and length of time that sanitizer is produced. Some systems are designed to check the water around the cell to determine the current chlorine level. If the level is low the controller switches on the salt cell. If the chlorine is high, then it will switch off the cell. Other systems enable users to select the length of time that the salt cell produces chlorine before it stops production and also how long it will wait until it starts production again.
The Hot Tub Wizard Controller provides 10 power levels
The total length of time that the salt cell is “energised” has a direct effect on the life of the salt cell. Most salt system manufactures recommend that the “run time” of the cell be minimised through the controller settings in order to maximise cell life. However don't run the salt cell for too little time to negate its effectiveness in your Spa Pool environment. Starting low, and then gradually increasing to your “happy point” is normally what is recommended.
Design of the salt cell electrodes varies between different manufactures. Some salt cells use electrodes with a reasonably low surface area in comparison to other systems. Other salt cells such as the Scepter use electrodes with a much larger surface area. The larger the surface area of the salt cell electrodes the more efficient the cell is in producing the chlorine sanitizer. e.g. it needs to run for a shorter period of time thus improving cell life.
Water Hardness
Due to well known water chemistry, the majority of salt water systems require a water hardness to be maintained of between 250 and 350ppm (parts per million). Some salt water systems recommend only 50ppm. For a salt water sanitising system to work reliably it is important to ensure that water hardness is maintained at the correct level. This can be checked with good quality water test strips.
If the spa pool is topped up with more water, it may be necessary to increase the water hardness level to the correct level by adding a “hardness increase” product.
Failure to keep the water hardness at the correct level, and allowing it to drop can dramatically reduce cell life. This is usually proceeded by the presence of fine grey flakes in the spa water. This is the special “titanium” coating on the salt cell electrodes detaching from the electrode surface.
Calcium Build-up
While it is important to maintain correct water hardness as per the range above, it does mean that there will be a gradual build-up of calcium deposits on the salt cell's electrodes. Such a build-up will reduce the salt cells effectiveness, and so the cell should be treated regularly (usually every month) to remove this build-up. While various proprietary products are available to treat the salt cell, the use of normal household white vinegar works well (immerse the cell electrodes in white vinegar for a half hour and then rinse and check – if white deposits still appear then repeat).
Correct Salt Levels
Having the correct salt concentration in your Spa Pool water is another important factor that you need to manage. Most manufactures recommend between 1500 and 2000ppm (parts per million) - the happy point being 1750ppm. Not enough salt and the Salt Cell does not have enough sodium chloride to do its job, and too much salt and the system at a certain level will cease to operate. Use salt test strips to keep an eye on your salt concentration, particularly after a water top up. Of course each time you replace your Spa Pool water you will need to also add the correct amount of salt before turning on your Salt Water System.
pH Levels
The importance of maintaining the correct pH levels in your Spa Pool water cannot be overstated in order to maintain effective water chemistry. With regard to Salt water systems, we have noticed that there appears to be over time a gradual increase in water pH which must be adjusted.
This occurs at a reasonably slow rate with new fresh water, but over time this pH increase seems to occur more rapidly. This must be manged through regular water testing, as high pH will also cause the titanium coating on the the Salt Cell electrodes to be damaged, and again this can be seen as grey flakes floating in you Spa Pool water. The less titanium coating left on the cell electrodes, the less efficient it becomes until it ceases to work.
Usage and Age
The more a Salt Cell has had to produce chlorine (the longer it is energised), the shorter its productive life will be. For some “lightly used” Spa pools (used on average by two people once every few weeks or so), the Salt Cell might last a number years. In “heavier use” environments, (where say the Spa Pool is used every day by a family), Salt Cell life may reduced to just 6 months life.
Over time the effectiveness of all Salt Cells reduce with age as they gradually wear. This means that the time that the Salt Cell is energised by the Salt System controller for each cycle will have to be gradually increased. What might start as running the Salt Cell at level 3 when first installed, then after 3 months have to be increase to level 4, then in another three months to level 5, etc. Judge the required power level increase based on the clarity of your Spa water. If it’s getting a green tinge then shock the water and increase one power level at a time.
Positioning
It is important to pay careful attention to where the Salt Cell is positioned in your Spa Pool. It is important to place the Salt Cell in a position where it is exposed to a reasonably high regular water flow (without the jets being run). This is ensure that the chlorine sanitiser is evenly distributed throughout the Spa Pool water and the cell does not have to be run for longer periods of time than necessary.
A popular location is the filter compartment beside the filter(s). In some cases it may be possible to position inside one of the filters but we have seen problems with this when the Salt Sell uses up all of the available salt in the body of water inside the filter. Another location is next to the water outlet vent in the deepest part of the Spa Pool. Experience has shown that lying the cell on its side prevents an air bubble forming in the top of the cell, and thus reducing sanitiser flow.
If possible, slide the Salt Cell down to the side of the filter for best circulation
In our experience, if you have a Spa Pool that does not constantly recirculate the water, then a Salt water system is not recommended unless you install some method of regular water circulation. This can be achieved through the use of a simple 12v boat bilge pump on a timer.
In Summary
There are many factors that contribute to Salt Cell life. Replacement Salt Cells are not inexpensive, so we recommend keeping a close eye on how your Salt Water system is performing and adjust it accordingly. Make sure you regularly clean your Salt Cell to maximise its performance.
If you believe you have a problem with a Scepter Salt Cell, and have followed all of the steps recommended, please feel free to contact us and arrange for it to be sent to us for testing.