Not sure if I may have a mustard Algae issue or not

[dmccarthy]

I have an inground, indoor gunite therapy pool at my business. (Please disregard my signature at the bottom as that is for my pool at home). Recently, there has been yellowish staining along some of the walls and near the deep end that does not seem to brush off. The indoor pool is approximately 24,000 gallons and is sanitized with bromine tablet with an in-line brominator. The temperature of the water is maintained 92 degrees. The water was just changed out about 3 months ago and the current measurements are as follows:

FC 2
PH 7.4
TA 110
CH 240
CYA 0

It is an indoor public pool, generally we try to keep the FC around 2-3 ppm, but recently I seem to be having difficulty maintaining the levels consistently and seems to be dropping faster than usual. We have an extremely high bather load (150 bathers/week) so I am used to adding bromine tabs and liquid chlorine regularly to keep up, but it seems to be going through more than usual to maintain. It does have a few skylights so I thought that maybe the fact that it seems to be going through sanitizer quickly and the FC/Br levels are not maintaining and the yellowish staining on the walls that maybe I could have a mustard Algae issue??

I had the pool water (and the fill water) tested today at the pool store for metals and they said there were none. My questions are Do I have a mustard algae issue? If so, should I SLAM for mustard algae and then do an OCLT? What level should I raise the FC to if my CYA is 0? I read 12 for MA but that is with CYA at 20ppm. Or, do you think it isn't a MA issue and could I possibly have something else?

Thanks in advance,
Darin

 

[tim5055]

You have me confused, are you sanitizing with bromine or chlorine? You talk about both in this thread.

 

[dmccarthy]

Bromine, but add liquid chlorine when shocking

- - - Updated - - -

Sorry, bromine tabs through an in-line brominator to maintain normal FC/Br levels. I add liquid chlorine as needed when levels drop or CC gets above .2ppm. Hope that clears it up.

 

[duraleigh]

that does not seem to brush off.

That's not mustard algae.

 

[dmccarthy]

any idea what it might be?

 

[dmccarthy]

I have never had this yellowing before on the gunite surface, especially after having just changed the water out 3 months ago. It is definately in patches in the deep end and some of the corners and steps. After a year or so and when we finally change the water out we may seem some mild discoloration on the surface, but not like this. Could it be something from the bathers? Otherwise, the water is clear and all the other measures appear to be normal. Other than that it seems to be going through bromine tabs more than usual to keep the bromine residual between 4-6ppm (around 2-3ppm on FC readings). I also seem to be adding liquid chlorine (12.5%) to the pool more than usual (2x/week) anywhere from 1/2 gallon to gallon to help reactive the bromine and keep the levels up between 4-6 and reduce the CC. I am aware that with bromine you can't distinguish between combined bromine and free available bromine and I am only testing the residual with that, however we use the taylor test kits that are recommended on this site for all the free, combined and total chlorine and residual bromine. Could it be a problem with my filter?? We have a 500lb high-rate sand filter that is about 5-6 years old.

Again, I had both the pool water and the fill water tested yesterday for copper, iron, etc at the pool store and nothing came up. Any suggestions on what you think it might be would be most appreciated.

Thanks

 

[Swampwoman]

Can you post a pic of the stains?

What is your water source?

Will a crushed up vitamin c lighten the stain?

Sometimes metals don't show on tests if the water has been sequestered, the metal has precipitated into a stain, etc. eg. I was once told by a pool store I had no metals...but I had all the signs and a wellwater source. I've since bought my own test and long since confirmed and treated for metals etc. but te point is had I "believed" the pool store I'd still be chasing my tail

 

[dmccarthy]

I will try and get you a pic later today. The water source is municipal. Do you recommend any test kits that test for metals that I could purchase to test on my own? I have not added any metal free or anything to the water, just some clarifier (usually weekly after shocking) and occasionally a few capfuls of pool perfect.

Can I do the crushed up Vitamin C underwater? Not sure how to do that. Could I hold a tablet against the pool wall underwater for a few min? Would that work?

Thanks

 

[ping]

Try brushing the stains with a stainless brush and post the results. Is the plaster pitted or rough in those areas?

 

[Swampwoman]

Can I do the crushed up Vitamin C underwater? Not sure how to do that. Could I hold a tablet against the pool wall underwater for a few min? Would that work?

That should work...you just want to see f the vit c effects any change, and should see a reaction or lightening in a minute or two if it is a metal stain.