Staining due to pool water

Staining in pool water can happen to the surfaces on all types of pool whether tiled, concrete or liner pools however the most common appears to be with liner pools.

There are a number of potential causes so it may be worth narrowing them down to what you think they may be problem.

Ruling out the obvious;

  1. Assuming it is not the standard tide mark (scum line) often more common in areas with hard water, this can usually be cleaned with a proprietary cleaner or what is commonly used is Sodium Bicarbonate.  It is always advisable to check the calcium hardness levels in the pool as too much will eventually lead to surface marking.
  2. The liner has not stained by sunlight, liners are usually treated to prevent UV light deterioration but they do not last forever.
  3. Adding chemicals directly into the pool particularly disinfectants can cause what is known as bleaching (fading).  It is always recommend that chemicals be mixed to a volume of water first before being added to the pool and when applying to the pool ensure it is distributed around the pool and not in one place.

If it’s none of the above then let us consider

Organic Materials;

Have you considered that it maybe organic stains which are usually brown or green, the cause of which may be the algae, dirt, mud, leaves or other organic material in the pool.

It is possible it may be due to bacterial build-up leaving a possible light pink colour, if this is the case then reviewing of the  disinfection levels in the water needs to be considered, not only to address the staining but to minimise the risks of cross infection.

Metal Staining:

If the organic staining is not the source of the staining then it may be due to the presence of metals in the water or the subsequent chemical reactions.   

Look for the obvious signs as to the culprits, particularly around the steps / ladders, pool outlets, skimmer baskets or any other water features in the pool.

The metal stains generally are from copper, iron and Manganese which may have been introduced during the addition of the mains (source water)

Copper stains – blue-green (teal)  Mainly due to the mains supply, possibly even a damaged calorifier heat exchange unit.   Have you added algaecide as this may contain copper sulphate (chelats) to kill the algae.   As an alternative you may want to think about Quaternary Ammonium compounds. (Be aware as these are basically a detergent it can lead to increased foaming but contain no copper).

However copper in the water has also been known to react with sun protection products worn by bathers, this can often lead to yellow staining.  If you think this is the case then check to see if you have elevated copper levels.   

Iron – will usually enter the water through the tap or source water.  If you have an old pool however you may want to check if there are still iron components installed.  These could be strainer baskets, pool fittings or the old iron pipes.

High levels of iron can leave reddish brown (rust) appearance but on some liners it can also cause  yellow staining

Manganese in the water often results in black or purple stains.  Manganese will tend to be introduced through the mains (source) water.  High levels you may see the water look a little discoloured although it’s not likely to be cloudy. When you add your disinfection oxidsation takes place and can result in a black or purple colour appearing as the water darkens.

Recommended levels for the chemicals;

Generally swimming pool water should have zero mg/l of copper or iron present.  As a guide we would recommend a maximum of 1mg/l of copper or iron.  If you start going over 0.3mg/l iron or copper then staining maybe the result.

Need further information

Want to test for the chemicals then let us know how we can help by emailing or calling 0115 8882726