stains on liner

[Guest David]

I have a 22,000 gallon in groud pool with a new liner that was put in last season. I check the chems on a regular basis and they are in proper adjustment. This sesason I have used a ton of chlorine both liquid and granular due to the extreme hot weather in the east. I am now getting brown staining on the pool floor. Any thoughts as to why this is happening?

[Guest Eric]

Brown stains is usually metal oxidizing in the water. Bring a water sample to a pool store and test for copper, iron and magnesium.

The metal may be comming from your source water, so also test the tap water.

The other possibility is that the metal is comming from your heater. To avoid metal corrosion, the pH, alkalinity and water hardness should be maintained in the recommended ranges. If your test kit only tests for pH and chlorine, throw it out! Invest in the Aquacheck Yellow 4-in-1 test strips.

Also, do you use copper based algaecides, or that magic blue powder? Read the labels and look out for coper sulfate! I would never use copper algaecides in vinyl pools, as there is always a risk of staining. 40% polyquat algaecides work just fine. The only trade secret is to apply the algaecide 24 hours after a shock treatment and not concurrently.

Also, how do you chlorinate? Do you use Trichlore pucks and shock the pool with liquid or granular chlorine? If so, Trichlore pucks are verry acidic and should NOT be placed in the skimmer, as this will corrode any heater. Pucks must be placed in a designated chlorinator installed on the return line after the heater to avoid corrosion. Also, a check-valve should be installed on the chlorinator to avoid back-flow of corrosive water into the heater.

The pool stores sell stain remover products. They sometimes work miracles, but often do nothing. Good luck! If there is metal in your water, buy a chealating agent which helps reduce and control metal in water.

P.S. Also test for stabilizer (cyanuric acid) and adjust it between 25 - 40 PPM. You may quickly discover that you only require half a ton of chlorine instead of a whole ton!

[Guest Eric]

One more possibility.

Liquid chlorine and granular calcium hypochlorite are both high in pH. You probably used pH reducer (sodium bisulfate) or muriatic acid to lower the pH. pH reducer or muriatic acid should be poured around the pool, and then the pool should be brushed to stir it up. (Note: muriatic acid is not recommended as it can damage the printed patern on a liner).

Pouring strong acid directly in the pool skimmer can certainly corrode a heater!