Any time you have different metals (copper, stainless steel, etc.) in a pool, you create a battery. Some amount of current flows between the metals. The electrons that make up the current are supplied by one of the metals, giving up bits of itself in the form of metal ions to the pool water. This is called galvanic corrosion. Galvanic corrosion causes plaster discoloration and metal erosion. The best way to inhibit the effect of galvanic corrosion is to use a zinc anode. Zinc is a metal that gives up its metal ions faster than other metals in the pool. In other words, the zinc anode will erode instead of other metals (pool light, rails, heater, light niche, ladder, etc.). The zinc ions will not discolor the pool plaster. The zinc anode should be replaced after half of it has eroded.
If you’ve looked through my website you know I’ve worked on many pools with rebar corrosion issues. Rebar stains are troublesome and costly. Trust me, you do not want one but if your pools reveals a rebar bleed you want to get it treated as quickly as possible- and, if it’s a salt water pool, timing is critical. Remember, SALT ACCELERATES THE CORROSION PROCESS! Rebar stains in salt water pools are ALWAYS more extensive than traditional chlorine pools. The longer you wait the more it spreads. It does not go away. Do you remember when your pool was built? Remember the spider web of rebar all tied together? Well, all the metal has the potential to rust. It may only start in one spot but it slowly spreads with the metal rebar acting like a fuel for the corrosion.
If you have a salt water chlorine generator I recommend having an anode in your pool as salt is so corrosive.
Pool Tool is the go-to supplier for swimming pool anodes.
You can find zinc balls on-line with a simple keyword search.
So, do zinc anodes truly work? Yes, they will inhibit corrosion, it’s to what degree that’s difficult to measure. Old-timers swear by them and for the amount of money you might spend repairing corroded rebar, $30 is worth it to me. I have one in my pool!