Automatic Liquid Chlorine Disinfection
Here we discuss how to achieve Principle 5 for obtaining Clear Clean Water.
Principle 5: Minimise chemical use by precise control systems
This relies on 24/7 running of the pool pump to ensure that every cubic metre of pool water passes through the UV cell at least 4 times in every 24 hours.
The instrumentation in the system accurately measures and adjusts the pH and Chlorine levels to ensure that your pool water has the exact minimum amount of chlorine required to ensure that the pool water is safe and healthy.
If the pool has a UV Cell, the chlorine levels can be reduced to about the same level (0.8 - 1.0 ppm) as the water from your tap (0.5-0.8ppm)
The equipment is fixed to the wall of your plant room and is equipped with two 25kg liquid containers. One is for pH stabiliser and the other is for calcium or sodium hypochlorite.
Two basic types of system:
Redox Systems
Redox systems measure the oxidizing properties of any sanitizer (chlorine) present in the water and are ideal for domestic pools. In simple terms they measure the oxidative power of the pool water and so provide a qualitative estimate of free chlorine which provides a good indication of how water quality has been affected by bather pollution. When chlorine is free to oxidize, sensors generate a millivolt reading, expressed as the oxygen reduction potential (ORP) and the controller responds to the level of voltage generated.
The Redox controller is commissioned by a technician after the pool has been filled and been in operation for a week or so. The technican calibrates the machine by measuring the pH and free chlorine in the pool water and setting it up accordingly. The readings are interpreted by the controller in the unit taking into account the millivolt reading and pH levels. The machine then injects the appropriate amounts of pH stabiliser and liquid hypochlorite into the water flowing back to the pool.
By ensuring that the pool water filtration system is never charged with excess chlorine the possibility of bleach damage to the pool's PVC liner is minimised. Maintenance is restricted to periodically filling up the chlorine and pH containers and the pool water quality will be maintained. This system is particularly ideal for Clients with a holiday home that they only visit occasionally.
Redox systems cost under £ 2000 + VAT and are relatively maintenance free and just require the replacement of the liquid chemical containers every 6 months or so. The probes and injectors need to be replaced occasionally and this normally carried out by the pool owner.
Free Chlorine systems
Amperometric or Free chlorine systems directly measure the level of free chlorines in the water and because the process is more complex the probes and the electronics - whilst similar in size and appearance - are a lot more expensive and their use is normally restricted to Commercial pools. They can cost up to £ 5,000 + VAT depending on the manufacturer but they normally give many years of useful life.
A typical dosing schematic is shown here:
This is a commercial system and includes coagulent dosing.
A domestic system with a UV cell will only require pH and liquid chlorine dosing.
For more details on the Bluepools' Principles and how to get the best quality for your pool, click the link below:
Clear Clean Water