brown spots near my return

[garyg]

Hi All:

I have been pretty obsessed about pool water chemistry since I had my 5 year old pool replastered this spring... I use the K 2006 test kit... my numbers...I have a SWG... FC 5.2 TC 5.2 PH 7.8 TA 70 CH 450 CYA 60...My CYA is a little low so I added conditioner yesterday..I know my CH is a little high... but..

My big problem is I am getting dark brown spots about the size of a dime near my return... No where else in the pool..What could it be and what do I have to do to keep these away.. when I brush hard with my wire algae brush (thanks waterbear) ... they go away.. only to return the next day... sometimes 2 or 3 and some days.. 6 to 10..color may have a tinge of yellow/green as well.. they have a tight splatter pattern..

help... what do I do..??

Gary

 

[JasonLion]

Try holding a vitamin C tablet against one of the stains for 30 seconds and see if that has any effect.

 

[garyg]

Jason:

very little if any effect... when I rub the vit. C on the spots it does reduce the size a little but I think that is more a result of the abrasive action then a chemical reaction.. gary

 

[JasonLion]

Hum, I was thinking iron, but that would have disappeared from the Vitamin C without any rubbing. Algae is possible, but really doesn't seem likely if your FC level is steady around 5 with a SWG.

Hopefully someone else has some ideas.

 

[garyg]

Jason:

My chemistry has been really good in I joined TFP and got educated... but I have seen people that are having similar problems, some of the pros ask about there pool filter... Mine is a huge cartridge filter ... 700 sq ft. and I have only cleaned the filters one time in 5 years because the pressure never really changes... It does flucuate because I have an infloor cleaning system but the highest pressure... 22# has never really varied..

the spots always seem to appear near the return and it happened a few years ago... before I replastered as well.

hope this helps..

Gary

 

[duraleigh]

Purely a guess, but with your CH and pH both a littler higher than they should be, that combination may be resulting in some precipitation.....perhaps calcium mixed with something else to give it the coloring.

That may be a bit of a stretch but you could drop your pH down to 7.0-7.2 and keep it there for a week or so and see if that didn't slow or eliminate it's return. Cheap and relatively painless to do and it may work.

 

[PoolOwnerNumber9]

01) What brand is your in-floor cleaning system?
02) How many in-floor pop-up cleaning heads are there?
03) How many floor returns do you have?
04) Are there any wall returns?
05) Is there a heater?
06) Are the spots only appearing near one return, or by multiple returns?
07) Do spots or stains appear in any pattern coming out of the pop-up cleaning heads?
08) Do the spots appear after adding water?
09) Do you add water through the skimmer or directly into the pool?

You should clean the cartridge filter. Only needing to be cleaned 1 time in 5 years is very unusual. You should also remove all of the in-floor pop-up cleaning heads and floor return covers and screws to allow any debris in the lines to be blown out. Be sure to not allow anything to fall into the open holes.

Replace the return covers and pop-up heads after clearing the lines. The returns have an adjustable plate that is adjusted by a screw. Be sure to adjust all returns to the same level. Check the in-floor cleaning system distribution head for any debris. Clean the screen that goes to the in-floor cleaning system distributor head.

Check the salt cell for scaling and clean if necessary. Also, have the pool water and fill water tested for copper and iron. The salt cell could be causing iron or copper to precipitate out. The cell generates chlorine gas and hydroxides, which could combine with iron to form brown iron oxide or Yellow iron hydroxide. A stain and scale controller chemical should help.

 

[garyg]

Hi... this is a response to poolowner9..

1. shasta... quik clean
2. 18
3. 2
4. yes (1)
5. No
6. only on floor near wall return
7. doesn't seem to be... since head rotates 360 degrees.. I would think that pattern would be the same around nearest head... that is not true.
8. no
9. directly into pool

there is no adjustments on the returns of this system that i can see...

salt cell is cleaned monthly... city of phx water... no iron or copper

The cartridge filter is so huge... 700 sq. ft.. the pressure has not exceeded 22# since it was installed...

what do you think is causing the problem..

Gary

 

[PoolOwnerNumber9]

I'm thinking that the cause is either a metal or an algae possibly concentrating on spots that have been etched by spot etching. You should try to control algae, etching and metals. For algae, proper free chlorine and brushing. For metals, a stain and scale control chemical. For etching, increase the saturation index to as close to 0.0 as you can without scaling the cell.

I can give you better advice if you do the following:

1) Clean the cartridge filter. Report, in as much detail as possible, what is trapped on the filter.
2) Remove all of the in-floor pop-up cleaning heads and floor return covers and screws to allow any debris in the lines to be blown out. Report, in as much detail as possible, what debris blows out.
3) Report a full set of chemical readings.
4) Explain, in as much detail as possible, the filtration and plumbing set-up and operation.
5) Clean the screen that goes to the in-floor cleaning system distributor head. Report what debris is trapped on the screen.
6) Check the spots carefully to see if they are a different texture than the surrounding plaster.
7) Place a women's knee-high stocking, or other such fine filter, over the outlet to trap any debris that is coming out of the line and then examine it carefully. Use a magnet to test for iron. Report results.

Another possibility is a leak in the return line. Sometimes a leak can act like a venturi and pull dirt into the line and then blow it into the pool. With this type of leak you may not get much, if any, water loss. The line can be pressure tested for leaks.

Or possibly the metal is coming from under the plaster. If the rebar, or rebar ties, are rusting; the rust can sometimes come up from under the plaster and cause metal discolorations. Look for pinholes, cracks or roughness at the discolorations.

 

[Guest]

I'm thinking that the cause is either a metal or an algae possibly concentrating on spots that have been etched by spot etching. .

I tend to agree but I lean more toward algae since the OP said that the color tends toward greenish in a earlier post.

I would follow poolownernumber9's suggestions in the post above. It's sound advice.

 

[PoolOwnerNumber9]

The fact that the stains appear only on the floor below the one wall return, in a " tight splatter pattern", is now making me think that the problem may be related only to the wall return.

If the return has a Venturi type crack, the intermittent staining may be due to water washing dirt into the crack after rain or watering of the yard. One indication of this type of leak could be tiny air bubbles coming out of the return when the salt cell is off. The salt cell does produce some small bubbles which could mask the problem. Using something to catch debris from the line for inspection would be very helpful.

 

[garyg]

HI :

lately they seem to have more of a brownish tint.. but I did try a vit. c tablet and had no effect... so jason thought it is not iron staining..

I have seem some of the spots in the deep end of the pool but not for over 6 weeks.. seems like when I brush them well... they are gone the next day..the chlorine level is been ok for a long time... how can algae bloom with a satisfactory chlorine level??

I could put something like a window screen material over the wall return and see if I get anything... but the spots have not returned for over 5 days now..

gary

 

[duraleigh]

Did you lower your pH down to 7.2? It's cheap, easy, and it may work.

Short of that, do an overnite FC loss test. Test your FC in the evening and then again the next morning. If you have no algae, your FC loss should be .5ppm or less.