Mustard Algae problem or not?

I think I may be dealing with mustard algae but it's confusing me since my cc level remains negligable. I'm getting a yellow blotchy dust coating on the bottom of my pool. Our pollen season is pretty much over and I'm not seeing any on vehicles in the morning so I don't think it's coming from the trees like earlier in the season and I had the pool clear when the pollen season was over.

A month ago I had the pool clear, it was holding 20ppm Cl overnight with no CC. I kept it there for about 4 days then let it drift down while keeping my SWG at 80% and circulating 8 hrs a day. When the pool gets to 12-15 Cl, it gets a little cloudy and the yellow dust starts settling on the bottom. The pool gets a lot of shade and some sun. Even with the water clouding and dust on the bottom, the CC tests O and sometimes .5. I've tried daily vacumming, brushing often, and clean the cartridge often but it doesn't go away, just kind of stays at a low level.

So, I decided to give the shocking another go and treat it like mustard algae. Last night I ran the Cl up to 25, turned off the swg for the night, and brushed the pool. This morning the Cl is 24, CC is 0-.5 and the yellow dust is a gray/blue color. So, my plan is keep the Cl at 25, brush daily, vacuum and clean filter every 2 days, SWG back on at 60% and run the pump 24/7. After a couple of days of this, I'll increase the Cl to 35 for a couple of days and let it drift back down if the CC stays at 0 and the water looks good. Does this sound reasonable, or should I use some Polyquat along the way for maintenance since it's been such a pain so far? I also think I was fighting it last year but not as bad.

One problem that I see for persistence and a return of the problem is that I have in floor cleaning and I've pulled a few of the heads that were broke. There is a light brownish deposit on the parts under the floor, from years of accumulations, it is not slimy. So, I'm sure that the pipes to the heads can have algae growing on these deposits, and there is no way to brush them to break it down.



Oh almost forgot, cya is 50-55, Ph reads high but with high Cl it's hard to put faith in the value, alk is high at 135 or so, CH is high at 500. I'm also working at changing out my pump and a larger filter but would like to clear the water up first.

Thanks for any suggestions for changes to what I'm doing to combat this or how to keep things at bay once it's gone. I'd like to not keep the Cl at 15-20 to keep the water clear.

Sorry this is a bit verbose, too much coffee this morning I guess!

It seems unlikely to me that it is algae with no chlorine consumption overnight and only a slight CC reading. Ben may think differently.

Just wanted to ask about that high CH reading? Are you using cal-hypo? If so, no more. That is pretty high and along with high pH and high alk may cause you some issues at some point. Also, don't use your salt cell to keep the pool at shock level. It will shorten the cell life. Use a different chlorine source and then once you are just back in maintenance mode, turn your SWCG back on.

I only use liquid chlorine in the bulk containers from the pool store for shocking. My fill water is ground water and I think the CH for it is like 250. I'll have to retest it and see. Metered water is pretty expensive in Fl so I use the irrigation well. It does have sulfer in it if that means anything. I suppose evaporation over the years could have concentrated the Calcium in the water. Yes, the very low CC reading has confused me on this issure and calling it algae. But strangely, as soon as I approach 20ppm with free Cl, the pool turns that cloudy blue gray just shocked look and starts to clear in a few days and holds the CL overnight. but when I let the Cl fall off after 3-4 days and when the level starts dropping below 15, it starts to cloud up again and the yellow color of the dust on the bottom takes hold again. Until that point, there is a small amount of clear gray dust on the bottom which I assume is dead organic debris or algae that didn't quite clear from the shock period.

I've asked Ben to take a look at this thread.

Quote:

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Originally Posted by keastman

But strangely, as soon as I approach 20ppm with free Cl, the pool turns that cloudy blue gray just shocked look and starts to clear in a few days and holds the CL overnight. but when I let the Cl fall off after 3-4 days and when the level starts dropping below 15, it starts to cloud up again and the yellow color of the dust on the bottom takes hold again..

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The fact that it recurs when you lower chlorine is indicative of mustard algae. Do all these things:

1. Tell us how you are testing (if your CYA test results are NOT from a K2006, or other Taylor CYA test, we're going to tell you to get one!)
2. I've never said this before, but go your pool store, and see if they will test for phosphates. It's very unusual for mustard algae to recur at 20 ppm FC with only 55ppm CYA.
3. If you are not using your Quick-Clean flow director, cut it off, and EITHER
3a. Put MIP adapters on each riser, and then FIP caps on each adapter. Then pour 2 gallons of 1:10 bleach mix down each pipe. OR
3b. Connect each pipe to the supply with a 1/2 PVC section, so a small amount of treated water goes continuously through each pipe
[ Stagnant pipe are potentially dangerous. It's rare, but there have been cases of very dangerous pathogens accumulating in these pipes, and then during a maintenance failure, infecting a swimmer. ]
4. Let your chlorine drop, but put a trichlor puck on a flat plastic lid (don't let it rest directly on the pool surface) on a 'mustard algae' area. If the mustard algae does NOT develop around the trichlor, that's very indicative of algae rather than something else.

Ben, thanks for your input. Yes, I'm using the K2006 kit I got via this site's link. A couple of years ago the pool store (one that used photmetric analysis which I don't trust) said I had very high phosphates and wanted to sell me some junk that I didn't buy. At that time, the suggestions on this site said if I wan't having problems don't worry about it. I'll take a sample to Pinch a Penny tomorrow and have the test for phosphates. They use titration mehthods, so I'm assuming are more accurate if they have a titration test for phosphates.

As to the floor inlets, the only other inlet for the pool is the venturi skimmer which is limited in return volume and the SWG enters through that, so I won't be able to cut off the diverter and cap the lines as you suggested. I do think that these runs could be at the root of the problem if it is mustard algae Starting last fall some of them broke down in a few of the zones and the cleaning heads popped out. So, those in those zones, all the water enters from the blown out head and the water in runs to the other heads in the zone probably doesn't move a lot since the remaining heads in the affected zones don't activate. Perhaps that's where the algae hides out. The heads are also the only returns for my spa. So, my plan will be to pull out all the heads in the pool. The zones will still operate independently, but every return in the zone will then have water flowing through them. I may also get an appropriate sized bottle brush and try to clean as deep as I can get into each opening. Then I'll jack the chlorine up as stated earlier.

I'll report back on the phosphate results.

sounds good.

OK Ben, I got the rest of the in floor heads out today and cleaned their outlets as well as possible with a brush. I had the water tested for phosphates and as I remember it was high. 500ppm or more. I think it was the last color on the scale they were using. So, do you think the phophates are feeding the algae problem. Of course they wanted to sell me their phosphate remover. I figured I'd wait until I hear from you. Eventually I'll need to fabricate a cap for those floor outlets with small holes in them so that no one gets a toe or hand caught in them.

If you recall my other thread in equipment, I'm also about to replace my 12o sq ft cart filter with a 320sq ft one and new pump, but am thinking I need to clear this up first. I've also got high alkalinity and high Calcium hardness, don't know if that's making anything worse also.

My FC was 16 this morning with a CC of less than 0.5. The yellow dust is now blue grey, water is clear with a slight haze. I'm brushing daily. Typical for this point of my shocking. My plan was to put the Chlorine to 25 to 30 now for 3-4 days. Where would you suggest I go from here with the phosphates etc.

Thanks again for your help.

I almost can't believe I'm saying this, but with 0.5 ppm phosphates, it might be worthwhile to try using a remover. I'd recommend wait for the new filter, though. The removers cloud the pool badly, and it will clean up better with the larger filter.

Meanwhile, keep the chlorine high.

If you want to do so, adding borax to reach a 60 ppm level would also help. On a 23K gal pool, you'd need about 100 lbs (22 boxes of 20 Mule Team borax) plus about 6 gallons of muriatic acid. Borates at that level do seem to inhibit mustard algae, from the reports we've seen.

PAC floc will also remove phosphates, if you use them as a drip feed ahead of your filter, and clean the filter before the floc can escape. But you'll DEFINITELY want the new filter first.

Thanks, I guess I'd better get to work on plumbing in the filter then. Is there any type of phospate remover that's better than another. I usually deal with Pinch a Penny for chlorine and CYA, so I'd probably get what they carry, unless there is one that works better. Looks like this could be the summer for borates also if that will help. Can you tell me if that effects the taste of the water at all? Not that we drink it!

I also remembered that I haven't used the spa in well over a year, so I dumped a bunch of chlorine in it and switched over the returns and drain to spa to cook the jet pipes and spa return pipes for a while. I've yanked my non functioning heat pump and we wont' be using the spa other than to look at. Perhaps I should slightly open the drain and return for it so pool water is always moving through sth spa piping. Or would just switching the valves weekly for a few minutes to the trick.

I'll let you know how it's going once I get the plumbing changed around.

OK Ben, I've been running my Free Cl between 25-29 for about 5 days with no CC and an overnight loss of 1-2ppm at most. The yellow has been gone for that period, only a small amount of clear dust on the bottom.
I'm about ready to stop the liquid chlorine and let the level settle while I continue brushing and vacuuming.

So, I tested my CYA tonight and it is down to 40 or just a bit under that when it was 50-55 when I started jacking up the Cl. My question is, will the high Cl levels interfere with the test or burn off CYA? I know you've written of the biofilm consuming the CYA, but I can't believe I'd have a viable biofilm at those Cl levels. There have been no significant rains or water added to the pool in this time frame. My pool does usually go down to "0" cya through the winter, so I figure that may be biofilm action.

Watermom, could you ask Ben to look at my last post and see what he thinks of the missing CYA. I've now stopped adding CL, still have the SWG off and am letting the Cl drop. It's come down from 28-18 in 48 hours with only the pump running. Water is still clear. I'm planning on switching back to 8 hrs a day on the pump and starting the swg again tomorrow. I will need to add more CYA again but am confused on where it went. I'm going to test it today and probably put a sock full in the skimmer. The pool is shaded for half the day.

The CYA test isn't that accurate -- technically, if you get a reading of 50 ppm, both 40 and 60 are in the range of error.

When you add in the fact that high chlorine slowly breaks CYA down, and the fact that you may well have had some water loss during cleaning and such (typical, through of course, I don't know that it happened in your case)

Thanks,

I guess I'll continue to let the Cl fall and then add CYA to get back to the 60+ range for my SWG when I turn it back on. Then keep my fingers crossed that the yellow scourge doesn't re-appear.