Hi Folks, I have been having trouble now for months with brown staining all over the pool. I have tried an ascorbic acid clean several times but after 5 or 6 days the stain always comes back. My phosphates a very high despite several attempts to use a coagulate and vacuum them from the pool. After using the Vitamin C I get what looks like soap flakes floating in the pool. I have never had a high reading for metals on any pool shop testing. I have had trouble with my multi port letting water back into the pool when I have been back washing and some sand so I am changing my multi port over on the weekend to fix this. I run a salt chlorinator which produces 35 grams an hour and as well as this I am having to add 2 litres of liquid chlorine a day. We do have a high bather load of 80 students a day as we run a swim school from our home pool. We have never had to add so much liquid chlorine in the past though so not sure why! As we operate 6 days a week anything we try is limited to doing in a small window from Saturday afternoon until Monday morning. Does anyone have any ideas that can help us????? Part of the ascorbic acid clean is to use a Phosphonic acid to hold the staining substance presumably a metal of some sort in solution. Would the use of this acid be giving me high reading for Phosphates???? I have been all over town to find a solution but no-one has any idea. I have had my water tested from the tap where I fill the pool from and nothing shows up. I use a heater which has brass fittings and copper heat exchanger but I have been told the colour stains are not consistent with those metals and no metals have been detected in the water any way. It is a real dilemma I am hoping someone can help me with.
Brown Stains and Phosphates
- Thread starter HSSS
- Start date
- May 23, 2015
- 25,733
- Pool Size
- 16000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Pentair Intellichlor IC-60
How old is the pool surface? Can you post a full set of test results.
Fiberglass pool surfaces are very hard to diagnose because it depends A LOT on the quality of manufacturer. FG surfaces can experience all sorts of weird staining if the gelcoat starts to break down and, depending on how much calcium carbonate is used in the manufacturing of the pool surface, low CH can sometimes cause problems (chalking of the surface). Cobalt staining is another problem with FG pools but that typically manifests itself as little black spots on the FG surface.
Typically with an ascorbic acid treatment, one first uses the AA to lift the stain and then sequestrant is added to hold the metal ion in solution. As the FC is raised back up from zero, the chlorine will destroy the AA and you'll initially get very high chlorine demand. Then, as the AA concentration is reduced to zero, the FC begins to hold. BUT, it is critical to NOT raise the FC too high or too fast as you begin to bring it back up (some people take weeks to raise their FC very slowly) since the FC can easily re-oxidize any metals in solution and cause the stains to reappear. You may need to find a different stain treatment method and one that might be specifically formulated for FG surfaces. I would contact Jack's Magic Company and talk to their techs. They have a wide array of chemistries available to help with staining and their technical support is very good. Hopefully they distribute their products to Australia.
As far as phosphonate sequestrants go, yes they will be oxidized by chlorine over time and converted to orthophosphates (PO4). Many pool owners that are heavy sequestrant users find that their pools have thousands to tens of thousands of ppb's (parts per billion) worth of phosphates in their water. There's no easy way to deal with it other than to switch to more expensive and, possibly less effective, chemistries such as poly-acrylic acid (PAA) or nitrilotriacetic acid (NTA).
Fiberglass pool surfaces are very hard to diagnose because it depends A LOT on the quality of manufacturer. FG surfaces can experience all sorts of weird staining if the gelcoat starts to break down and, depending on how much calcium carbonate is used in the manufacturing of the pool surface, low CH can sometimes cause problems (chalking of the surface). Cobalt staining is another problem with FG pools but that typically manifests itself as little black spots on the FG surface.
Typically with an ascorbic acid treatment, one first uses the AA to lift the stain and then sequestrant is added to hold the metal ion in solution. As the FC is raised back up from zero, the chlorine will destroy the AA and you'll initially get very high chlorine demand. Then, as the AA concentration is reduced to zero, the FC begins to hold. BUT, it is critical to NOT raise the FC too high or too fast as you begin to bring it back up (some people take weeks to raise their FC very slowly) since the FC can easily re-oxidize any metals in solution and cause the stains to reappear. You may need to find a different stain treatment method and one that might be specifically formulated for FG surfaces. I would contact Jack's Magic Company and talk to their techs. They have a wide array of chemistries available to help with staining and their technical support is very good. Hopefully they distribute their products to Australia.
As far as phosphonate sequestrants go, yes they will be oxidized by chlorine over time and converted to orthophosphates (PO4). Many pool owners that are heavy sequestrant users find that their pools have thousands to tens of thousands of ppb's (parts per billion) worth of phosphates in their water. There's no easy way to deal with it other than to switch to more expensive and, possibly less effective, chemistries such as poly-acrylic acid (PAA) or nitrilotriacetic acid (NTA).