CO2 System

Automatic pH Control

Programmable Controller with pH sensor automatic control of either CO2 or acid feeder

It is important to balance the water in all pools to prevent corrosion (if pH is too low) or scale (if pH is too high). In a chlorine-free pool, the water is generally in balance at neutral pH ( 7.0, or 6.8 - 7.2). [If the pH in a chlorine pool were neutral, the aggressive chlorine would corrode the copper in the water heater.] The pH in most plaster/cement-based pools tends to climb to around 8.0 if no acid is added. The neutral pH can be maintained (lowered) with muriatic (hydrochloric) acid or with carbon-dioxide (CO2), which forms carbonic acid when mixed with water. This weak acid reverts back to CO2 and water when it breaks down, and is always totally harmless. Copper ions are most effective at neutral pH in preventing microbes and algae from living in the water (see bottom of Science page for details).

The 20 pound CO2 cylinder shown here is usually used for hot tubs. Two, 50 pound cylinders with auto-pressure-switch-over are usually used for pools.

Each high-pressure CO2 cylinder will last around a month, depending on the cure-level/age of pool, and can be exchanged for a full one by any welding shop or microbrewery for twenty-some dollars (plus delivery of about $18 if so-desired, or tanks can be exchanged by your pool service provider).

There are advantages and disadvantages to each of these methods. A CO2 system is the purest. However, an acid-feeder is less expensive to buy and to operate, much easier to re-supply, and more reliable. Most of the world's pools use muriatic acid, which is mainly hydrochloric acid, which our stomachs use to digest proteins. So it is not foreign to our bodies. In its concentrated form, it is caustic, so care is needed in handling and storing it, but once in the pool, it becomes neutral and harmless.