Pool Stain Busters - Ipswich Pool & Spa Centre

Treating Stains on Pools and Spas

HOW TO REMOVE STAINS

All you need to know about metal and organic stains

Stains are a common occurrence in pools but nothing about stains is simple. There is no simple 1,2,3 for stains. What works well on one stain may not be nearly so effective on the next.

No two pool owners will describe the same stain in the same way. What appears brown to one pool owner will appear green to the next.

The first rule of stain removal is to test the stain.
The second rule is you cannot always remove stains

What are stains?

A stain is something that alters the appearance of the pool surface to the detriment of the pool. This definition includes scale and most pool owners would indeed call scale a stain. Metals and dirt usually color the scale.

Scale is not a stain. It is a deposit of calcium carbonate, also known as chalk, on the pool surface. You can recognize it by its milky appearance and rough texture, which feels like sandpaper.

Stains can be the size of a hair clip or to where the whole pool surface is stained.

It is rare to find a pool that does not have stains of some description and it is a case of what the pool owner sees as beyond acceptable that determines if or when you will be called in.

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What causes stains?

Stains mainly happen when metals enter the water. These metals react with chlorine or the slightly alkaline pH. This reaction creates dark-colored metal oxides, which we refer to as stains.

Metals can be introduced by:

Salt added to a salt water pool – Salt is the most common cause of stains. Iron can cause stains that range from green to yellow to brown, depending on how severe it is. Manganese creates dark brown to black stains.
Liquid Chlorine. – Whose yellow colour is usually Iron. After continuous use for years the Iron build up can cause yellow to brown stains.
Top up water – Especially bore water which can contain Iron, Manganese or Copper.
Algaecides containing metals – May include Copper, Silver and/or Nickel, all of which give black stains.
Metal fixtures – Especially in Above Ground pools where the ladder and walls are made of cheap stainless steel which give Iron stains.
Garden dirt – Washed into the pool after heavy rain or hosing. May contain Iron, Manganese, Vanadium, Copper to name a few.
Black Spots in Fibreglass Pools – The Black Spots are Cobalt Oxide stains. The Cobalt comes from the gel coat. It leaches some of the Cobalt catalyst from the fiberglass resin. Blisters appear at the site of the black spot, characterizing osmosis.
Organic stains – From Algae growth, leaf stains or dirt washed into the pool and left longer than a week. Usually yellow to green.
Oxidation – Of fibreglass or painted surfaces which give a milky or chalky appearance. Oxidation isn’t solely due to elevated Chlorine levels, but rather a combination of high Chlorine levels and a low pH. Trichlor Tablets, which possess both high Chlorine concentration and a low pH, require particular attention!
Scale – Deposited on the surfaces of the pool giving a chalky or milky appearance and a sandpaper like feel. Scale is caused by:
Water out of balance from too high pH, too high Total Alkalinity, too high a Calcium level or too high T.D.S.

Look for the cause:

There is nothing worse than spending time and effort in removing a stain only to have it reappear after three weeks. This is a highly common scenario when using something like Citric Acid. The initial dose works well but Chlorine slowly breaks down the Iron/Citric Acid complex and the stain reappears.

Remember to look for the cause. Salt is the main cause of stains in pools. It is important for pool owners to understand that stains are a constant issue in saltwater pools.

Testing the stain

Testing the stain will determine what caused it so you can prevent it, what the stain is made of and how long it will take to remove or if it is possible to remove the stain completely.

Usually a pool owner will have some clue as to how the stain formed.

Was it after adding salt?
A Copper based Algaecide?
Do they have an Ioniser?
Do they have a leaf problem and leave the leaves sit in the pool for weeks?
Did a storm wash dirt into the pool?
How long has the stain been there? Have they tried anything themselves?

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Organic stains:

Most commonly leaf stains, where a leaf has been allowed to sit in one place for weeks and Algae stains where the pool was allowed to stay green for weeks. Dirt also gives rise to organic stains.

Dirt can wash into the pool after a storm. It can also happen if the hydrostatic valve works and dirty water comes in. You can tell this by a discolored ring around the main drain.

The most common colours are yellow, green and brown.

Metal stains:

Most commonly Iron which gives yellow through to brown stains and Black Spots in Fibreglass pools which are Cobalt stains.