Mustard Algae problem or not?

[Watermom]

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.

[keastman]

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.

[Watermom]

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

[PoolDoc]

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..

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.

[keastman]

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.

[PoolDoc]

sounds good.

[keastman]

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.

[PoolDoc]

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.