Boron, the fifth element on the periodic table, is found in naturally occurring minerals called borates (sodium borates). Borates are very cost effective, multi-action pool additives. Unlike chemicals that must be constantly added to the pool, borates are added just once and are only added again to compensate for water removal during backwash or drain down for winterization. It only takes about 40- to 60 parts-per-million to gain the many benefits that boron provides to pools.
Yes, that includes saltwater pools, which we’ll get to later. But first, let’s look closely at how this mineral works to improve water quality.
One of the biggest impacts reported by customers is the look and feel of the pool. The borate actually increases the refractory index of the water so more light is reflected — in essence, the pool sparkles. And because the borates are a mineral salt, they give the water a silky smooth feeling similar to a mineral bath.
Borates for use in pools come in two basic forms: Powder and liquid. Most borate powders will raise the pool pH too high, requiring the addition of acid to bring the pool into balance; however, the newer liquid borate products are based on hexaborate (pH 7.5) rather than tetraborate (pH 9) and so adjust the pool pH directly to 7.6-7.8 (the still slightly higher pH helps the chlorine perform longer). The liquid borate was developed to overcome one of the shortcomings of the powders, mainly dissolution. The powder formulas are difficult to mix into the pool — some of the powder will float on the top and some of the powder can sink to the bottom and form small hard clumps, and if added to skimmers, can actually damage pumps. The liquid borate simply needs to be shaken thoroughly and then poured into the pool for it to dissipate rapidly.
Chemically, the main benefit of borate is as a buffer. This feature stabilizes pH, which in turn extends the life of sanitizers, such as chlorine; stops acid degradation of pools; and prevents scaling at high pH. If the water has too much acid, the chlorine causes eye irritation and also is rapidly lost from the pool. The water will dissolve plaster, corrode metal fixtures in the pool and cause staining. When there is too much base in the pool, the chlorine works poorly, doesn’t kill all the bacteria and the water gets cloudy.
In addition to eye irritation, scale and discoloration, the pump has to work harder. Any type of pool with proper boron levels will allow the owner to reduce the amount of time they run their pump. Time reductions of 40 percent are common and we have seen pools reduce pump run time as much as 70 percent with the pool still maintaining a beautiful appearance. That can represent a $300 savings annually on a 15,000-gallon pool.
For pool owners with non-chlorine pools there also are great advantages to using borate. One of the problems with chlorine-generating pools using salt is that this continually generates NaOH when the NaCl is broken to free chlorine. This rapidly increases pH and requires addition of acid every 48 hours to maintain a safe pool with regard to the presence of hypochlorous acid. In saltwater chlorine-generating pools, the pump time reductions can be even greater with less salt and acid needed, as well as longer life expectancies on electrodes.
Borates’ buffering capacity allows the water to stay at a more neutral pH for longer, and so maintains its sanitation efficiency more effectively.
Pools run with biguanide sanitizers also get great advantages from the biostatic qualities. Borates help prevent the bacterial and algal sliming common with these systems. Many pool professionals run higher levels of borate in their pools for this algal control benefit alone.