After a hiatus for opening season, we are back with part two of our deeper look into chemical feeders and sanitization generators.
Mechanized chemical feeders used with what we call “automation”— (remotes, apps on your phone, preprogrammed schedules and doses)—can make water treatment as easy as opening your garage door—with the touch of a button.
Some common types of automated mechanized feeders include erosion (or mechanized) feeders, chlorine generators, ozonators, ionizers and mineral systems.
Erosion feeders are differentiated from floating tab dispensers because the tab dispenser is classified as non-mechanized, and the erosion feeder is mechanized. However, the fundamental “how it works” is very similar: the chemical is gradually eroded by friction of water passing over and around the chemical. There are two main types of erosion feeders, Inline pressure and Off-line pressure differential (also called bypass). An inline feeder is one that is plumbed straight into your system, typically after the heater, and the pool water that is being pushed by the pump creates that pressure which erodes the chemical. An off-line feeder is one that is not plumbed into the system, but is connected via tubing, taking some water from the pressure side of the feeder and returning it to the pressure line further downstream. The pressure differential is maintained by either a venturi pipe section, or gate valve. This will restrict waterflow and increase water pressure on the upstream side of the feeder. Simple physics wins again!
(An example of an offline pressure differential chlorinator-note the tubing that connects the chlorinator to two ports in the pool's system.)
As we continue, you’ll notice that sanitization options grow more sophisticated. Ever heard of a saltwater pool? Many people tout these as “chlorine free” but really the salt cell, or salt chlorine generator, uses low-voltage direct current to release the chlorine from the salt molecule. In simple terms, it uses the salt in the water to produce chlorine, which in turn keeps the pool sanitized. Many people opt for salt pools because they reduce the hassle of handling, storing, and moving chlorine, the salt cell handles all that for you. Typically, you only need to up your salt content once or twice a season, and it is much more economical than continually repurchasing chlorine as needed.
(Examples of a Hayward salt cell and Jandy salt cell on a couple of Denscot systems. Note how each cell is plumbed after the pump and filter, and the return line disappears into the ground just after the salt cell, taking freshly chlorinated water back to the pool.)
In water with high calcium levels, the chlorinator cell may scale, requiring frequent acid cleaning. Units called bipolar cells offer current reversal, to help clean scale off the chlorine producing plate. When the current is reversed, the plate repels the accumulated scale. Bipolar cells are shorter-lived than monopolar (non-current reversing) cells, but do not require cathode cleaning as often.
Additional disinfection and sanitization methods include ozone and ionizers. Ozone is produced and used on-site via UV light and electricity. Ozone reduces the need for chlorine, but does not replace it, being added back to the system after the pump, filter, heater, and often after the addition of a chlorine product. It is pH neutral and won’t cause the pH in the pool water to bounce.
Ionizers deliver measured amounts of silver, or silver and either copper or zinc ions into the water. These metals have bacteria and algae killing properties. There are other metal-releasing devices that rely on water that flows through the pool’s system to release these ions. Ionizers, like ozonators, must be used with a sanitizer like chlorine or bromine for regular sanitization, and if you are going to use an ionizer, remember to check with the local department of health, as some jurisdictions have restrictions on ion treated wastewater being discharged into a storm drain.
Whatever your preferred method of sanitizing your pool or spa, none are as important as the simple objective of keeping that water clean, for the health of your family, and the health of your system. As you look to build or update your system, talk to different pool professionals about what methods they recommend and why. There is so much more information and experience out there than can be fit into a couple of blog entries.